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A    TREATISE 


HUMAN    PHYSIOLOGY; 


DESIGNED    FOR    THE    USE    OF 


STUDENTS  AND  PEACTITIONERS  OF  MEDICINE. 


BY 

JOHN  C.  DALTON,  Jr.,  M.  D., 

PKOFESSOR  OP  PHTSIOLOSY  AND  MICROSCOPIC  ANATOMT  IS  THE  COLLEGE  OF  PHYSICIANS  AND  StTEGEONS 

HEW  TORE  ;    MEMBER   OP  THE   NEW  YORK  ACADEMY  OF    MEDICINE  ;    OF  THE    NEW  YORK 

PATHOLOGICAL  SOCIETY  ;   OF  THE  AMERICAN  ACADEMY  OP  ARTS  AND  SCIENCES, 

BOSTON,    MASS.  ;    AND   OP   THE   BIOLOGICAL  DEPARTMENT  OF   THE 

ACADEMY  OF  NATURAL   SCIENCES  OF  PHILADELPHIA. 


S^^irb  ^hxtion,  ^zbht)i  unh  ®ttlarg£b. 


TWO  HUNDRED  AND   SEVENTY-THREE  ILLUSTRATIONS. 


PHILADELPHIA: 

HENRY    C.    LEA. 

1866. 


3f 


ExTEEED  according  to  the  Act  of  Congress,  in  tlie  year  1864,  by 

BLANCHARD   AND   LEA, 

in  tlie  Office  of  the  Clerk  of  the  District  Court  of  the  United  States  in  and  for 
the  Eastern  District  of  the  State  of  Pennsylvania. 


PHILADELPHIA: 
COLLINS,  PRINTER,  705  JAYNE  STREET. 


TO    MY    FATHER, 

JOHN  C.  DALTOl^,  M.D., 

IN 

HOMAGE    OP    HIS    LONG    AND    SUCCESSFUL    DEVOTION 

TO    THE 

SCIENCE  AND  ART  OF  MEDICINE, 

AND    IN 

GRATEFUL  RECOLLECTION  OF  HIS  PROFESSIONAL  PRECEPTS  AND  EXAMPLE, 

IS    RESPECTFULLY   AND   AFFECTIONATELY 
INSCEIBED. 


(    iii    ) 


PREFACE  TO  THE  THIRD  EDITION. 


In  the  present  edition  of  this  work,  the  general  plan  and  arrange- 
ment of  the  two  former  ones  are  retained.  The  improvements  and 
additions  which  have  been  introduced  consist  in  the  incorporation 
into  the  test  of  certain  new  facts  and  discoveries,  relating  mainly 
.to  details,  which  have  made  their  appearance  within  the  last  three 
years.  Such  are  the  experiments  of  the  author  with  regard  to  the 
secretion  and  properties  of  the  parotid  saliva  in  the  human  subject, 
and  the  quantitative  analysis  of  this  fluid  by  Mr.  Perkins;  the 
valuable  observations  of  Prof.  Austin  Flint,  Jr.,  on  Stercorine, 
Cholesterin,  and  the  effects  of  permanent  biliary  fistula,  and  those 
of  Prof.  Jeffries  Wyman  on  Fissure  of  Hare-lip  in  the  median 
line,  from  arrest  of  development.  Three  new  illustrations  have 
been  introduced,  one  of  which  (Fig.  183)  replaces  a  previous  one. 
The  author  is  much  indebted  to  his  friend.  Dr.  Foster  Swift,  for 
aid  in  carrying  the  work  through  the  press. 

New  Yokk,  January,  1864. 


(V) 


PREFACE  TO  THE  SECOND  EDITIOl^. 


In  presenting  a  new  edition  of  this  work,  tiie  author  desires  to 
express  his  sincere  acknowledgments  to  his  professional  brethren 
for  the  very  favorable  manner  in  which  it  was  received  at  the 
time  of  its  first  appearance,  two  years  ago.  In  the  present  edition, 
the  author  has  endeavored  to  supply,  as  fully  as  possible,  the 
deficiencies  which,  he  is  well  aware,  existed  in  the  former  volume. 
Some  of  these  deficiencies  were  evident  to  his  own  mind,  while 
others  were  indicated  by  the  suggestions  of  judicious  criticism. 
These  suggestions,  accordingly,  have  been  adopted  in  all  cases  in 
which  they  appear  to  be  well  founded,  and  not  inconsistent  with 
the  general  plan  of  the  work.  In  those  instances,  on  the  other 
hand,  in  which  the  views  of  the  author  on  physiological  questions 
seemed  to  him  to  be  positively  sustained  by  the  results  of  observa- 
tion, he  has  retained  these  views  unchanged  in  the  present  edition. 
At  the  same  time,  he  has  abstained,  as  before,  from  the  lengthened 
discussion  of  theoretical  points,  and  has  purposely  avoided  even 
the  enumeration  of  new  experiments  and  observations,  wherever 
they  have  not  materially  affected  the  position  of  physiological 
doctrines;  for  in  a  work  like  the  present,  it  is  not  the  object  of 
the  writer  to  give  a  detailed  history  of  physiological  science,  but 
only  such  prominent  and  essential  points  in  its  development  as 
will  enable  the  reader  fully  to  comprehend  its  actual  condition  at 
the  present  time. 

The  principal  additions  and  alterations  which  have  thus  been 
found  advisable  are : — 

First,  the  introduction  of  an  entire  chapter  devoted  to  the  con- 
sideration of  the  Special  Senses,  which  were  only  incidentally  treated 

of  in  the  former  edition. 

(  vii  ) 


viii  PREFACE    TO    THE    SECOND    EDITIOjS', 

Second,  the  re-arrangement  of  tlie  chapter  on  the  Cranial  Nerves, 
and  the  introduction  of  some  new  views  and  facts  in  regard  to  their 
physiology. 

Third,  an  account  of  some  new  experiments,  original  with  the 
author,  relating  to  the  function  of  the  Cerehellum,  and  the  conclu- 
sions to  which  they  lead. 

Fourth,  certain  considerations  respecting  the  general  properties 
of  Sensation  and  Motion,  as  resident  in  the  nervous  system,  which 
are  important  as  an  introduction  to  the  more  detailed  study  of 
these  functions. 

Fifth,  the  introduction  of  a  chapter  on  Imbibition  and  Exhalation 
and  the  functions  of  the  Lymphatic  System;  including  the  study  of 
endosmosis  and  exosmosis,  and  their  mode  of  action  in  the  animal 
frame,  the  experiments  of  Dutrochet,  Chevreuil,  Grosselin,  Matteucci, 
and  others,  on  this  subject,  the  constitution  and  circulation  of  the 
lymph  and  chyle,  and,  finally,  a  quantitative  estimate  of  the  entire 
processes  of  exudation  and  reabsorption,  as  taking  place  in  the 
living  body. 

Additions  have  also  been  made,  in  various  parts,  to  the  chapters 
on  Secretion,  Excretion,  the  Circulation,  and  the  functions  of  the 
Digestive  Apparatus.  In  every  instance,  these  alterations  have 
been  incorporated  with  the  text  in  such  a  manner  as  to  avoid,  so 
far  as  possible,  increasing  unnecessarily  the  size  of  the  book. 

Twenty-two  new  and  original  illustrations  have  been  introduced 
into  the  present  volume,  of  which  number  five  replace  others  in 
the  former  edition,  which  were  regarded  as  imperfect,  either  in 
design  or  execution.     The  remaining  seventeen  are  additional. 

It  is  hoped  that  the  above  alterations  and  additions  will  be  found 
to  be  improvements,  and  that  they  will  enable  the  work,  in  its  pre- 
sent form,  to  accomplish  more  fully  the  object  for  which  it  was 
designed. 

New  York,  February,  1861. 


PIIEFACE  TO  THE  EIEST  EDITIOl^. 


This  volume  is  offered  to  the  medical  profession  of  the  United 
States  as  a  text-book  for  students,  and  also  as  a  means  of  commu 
nicating,  in  a  condensed  form,  such  new  facts  and  ideas  in  physio- 
logy as  have  marked  the  progress  of  the  science  within  a  recent 
period.  Many  of  these  topics  are  of  great  practical  importance  to 
the  medical  man,  as  influencing,  in  various  ways,  his  views  on 
pathology  and  therapeutics;  and  they  are  all  of  interest  for  the 
physician  who  desires  to  keep  pace  with  the  annual  advance  of  his 
profession,  as  indicating  the  present  position  and  extent  of  one  of 
the  most  progressive  of  the  departments  of  medicine. 

It  has  been  the  object  of  the  author,  more  particularly,  to  pre- 
sent, at  the  same  time  with  the  conclusions  which  physiologists 
have  been  led  to  adopt  on  any  particular  subject,  the  experimental 
basis  upon  which  those  conclusions  are  founded;  and  he  has  en- 
deavored, so  far  as  possible,  to  esitablish  or  corroborate  them  by 
original  investigation,  or  by  a  repetition  of  the  labors  of  others. 
This  is  more  especially  the  case  in  that  part  of  the  book  (Section 
I.)  devoted  to  the  function  of  Nutrition;  and  as  a  general  thing, 
throughout  the  work,  any  statement  of  experimental  facts,  not 
expressly  referred  to  the  authority  of  some  other  writer,  is  given 
by  the  author  as  the  result  of  direct  personal  observation. 

The  illustrations  for  the  work  have  been  prepared  with  special 
reference  to  the  subject-matter ;  and  it  is  hoped  that  they  will  be 
found  of  such  a  character  as  materially  to  assist  the  student  in 
comprehending  the  most  important  and  intricate  parts  of  the  sub- 
ject. It  is  more  particularly  in  the  departments  of  the  Nervous 
System  and  Embryonic  Development  that  simple,  clear,  and  faithful 

(ix) 


X  PREFACE    TO    THE    FIRST    EDITION. 

illustrations  are  indispensable  for  the  proper  understanding  of  the 
printed  descriptions ;  the  latter  being  often  necessarily  somewhat 
intricate,  and  requiring  absolutely  the  assistance  of  properly 
arranged  figures  and  diagrams.  Of  the  two  hundred  and  fifty- 
four  illustrations  in  the  present  volume,  only  eleven  have  been 
borrowed  from  other  writers,  to  whom  they  will  be  found  duly 
credited  in  the  list  of  woodcuts. 

Of  the  remaining  illustrations,  prepared  expressly  for  the  pre- 
sent work,  the  drawings  of  anatomical  structures,  crystals,  and 
microscopic  views  generally  were  all  taken  from  nature.  The 
diagrams  were  arranged,  for  purposes  of  convenience,  in  such 
a  manner  as  to  illustrate  known  anatomical  or  physiological  ap- 
pearances, in  the  most  compact  and  intelligible  form. 

Physiological  questions  which  are  in  an  altogether  unsettled 
state,  as  well  as  purely  hypothetical  topics  have  been  purposely 
avoided,  as  not  coming  within  the  plan  of  this  work,  nor  as  calcu- 
lated to  increase  its  usefulness. 

New  York,  January  1,  1859. 


C01(TE1(TS. 


INTRODUCTION. 

PAGE 

Definition  of  Physiology — Its  mode  of  study — Nature  of  Vital  Phenomena — 
Division  of  the  subject        .         .         .         .    ■ 49-59 


SECTION    I. 
NUTEITION. 


CHAPTER    I. 

PROXIMATE  PRINCIPLES  IN  GENERAL. 

Definition  of  Proximate  Principles — Mode  of  their  extraction — Manner  in  which 
tliey  are  associated  with  each  other — Natural  variation  in  their  relative 
quantities — Three  distinct  classes  of  proximate  principles  .         .         .         61-68 

CHAPTER    II. 

PROXIMATE  PRINCIPLES  OF  THE  FIRST  CLASS. 

Inorganic  substances — Water — Chloride  of  Sodium — Chloride  of  Potassium — 
Phosphate  of  Lime — Carbonate  of  Lime — Carbonate  of  Soda — Phosphates  of 
Magnesia,  Soda,  and  Potassa — Inorganic  proximate  principles  not  altered  in 
the  body — Their  discharge — Nature  of  their  function  ....         69-78 

CHAPTER    III. 

PROXIMATE  PRINCIPLES  OF  THE  SECOND  CLASS. 

Starch — Percentage  of  starch  in  different  kinds  of  food — Varieties  of  this 
substance — Properties  and  reactions  of  starch — Its  conversion  into  sugar — 
Sdgar — Varieties  of  sugar — Physical  and  cliemical  properties — Proportion 
in  different  kinds  of  food — Fats — Varieties — Properties  and  reactions  of  fat 
— Its  crystallization — Proportion  in  different  kinds  of  food — Its  condition  in 
the  body — Internal  production  of  fat — Origin  and  destination  of  proximate 
principles  of  this  class        .        , 79-94 

(  xi  ) 


Xll  CONTEXTS. 


CHAPTER    lY. 

PROXIMATE  PRINCIPLES  OP  THE  THIRD  CLASS. 

PAGE 

General  characters  of  organic  substances — Their  chemical  constitution — Hygro- 
scopic properties  — Coagulation  — Catalysis — Fermentation — Putrefaction — 
Fibrin — Albumen — Casein — Globuline — Pepsine- — Pancreatine — Mucosine — 
Osteine  —  Cartilagine  —  Musculine  — Hsematine — Melanine —  Biliverdine  — 
Urosacine — Origin  and  destruction  of  proximate  principles  of  this  class     95-104 

CHAPTER    Y. 

OF  FOOD. 

Importance  of  inorganic  substances  as  ingredients  of  food — Of  saccharine  and 
starchy  substances — Of  fatty  matters — Insufficiency  of  these  substances 
when  used  alone — EfiFects  of  an  exclusive  non-nitrogenous  diet — Organic 
substances  also  insufficient  by  themselves — Experiments  of  Magendie  on 
exclusive  diet  of  gelatine  or  fibrin — Food  requires  to  contain  all  classes  of 
proximate  principles — Composition  of  various  kinds  of  food — Daily  quantity 
of  food  required  by  man — Digestibility  of  food — Effect  of  cooking      .     105-114 


CHAPTER    YI. 

DIGESTION. 

Nature  of  digestion — Digestive  apparatus  of  fowl — Of  ox — Of  man — Mastica- 
tion— Varieties  of  teeth — Effect  of  mastication — Saliva — Its  composition — 
Daily  quantity  produced — Its  action  on  starch — Effect  of  its  suppression — 
Function  of  the  saliva — Gastric  Juice,  and  Stomach  DiGESTiojf — Structure  of 
gastric  mucous  membrane — Dr.  Beaumont's  experiments  on  St.  Martin — 
Artificial  gastric  fistulse — Composition  and  properties  of  gastric  juice — Its 
action  on  albuminoid  substances — Peristaltic  action  of  stomach — Time  re- 
quired for  digestion — Daily  quantity  of  gastric  juice — Influences  modifying 
its  secretion — Intestinal  Juices,  and  the  Digestion  of  Sugar  and  Starch — 
Follicles  of  intestine — Properties  of  intestinal  juice — Pancreatic  Juice,  and 
THE  Digestion  of  fat — Composition  and  properties  of  pancreatic  juice — Its 
action  on  oily  matters — Successive  changes  in  intestinal  digestion — The  large 
intestine  and  its  contents llS-lffl 


CHAPTER    YII. 

ABSORPTION. 

Closed  follicles  and  villi  of  small  intestine — Peristaltic  motion — Absorption 
by  bloodvessels  and  lymphatics — Chyle — Lymph — Absorbent  system— Lac - 
teals  and  lymphatics — Absorption  of  fat — Its  accumulation  in  the  blood 
during  digestion — Its  final  decomposition  and  disappearance      .         ,     162-174 


CONTENTS.  Xlli 

CHAPTER    Till. 

THE  BILE. 

PAGE 

Physical  properties  of  the  bile — Its  composition — Biliverdine — Cholesterin — 
Biliary  salts — Their  mode  of  extraction — Crystallization — Glyko-cholate  of 
soda — Tauro-cholate  of  soda — Biliary  salts  in  different  speciefi  of  animals 
and  in  man — Tests  for  bile — Variations  and  functions  of  bile — Daily  quan- 
tity— Time  of  its  discharge  into  intestine — Its  disappearance  from  the  ali- 
mentary canal — Its  reabsorption — Its  ultimate  decomposition  .  .     175-199 

CHAPTER    IX. 

FORMATION   OP   SUGAR   IN   THE   LIVER. 

Existence  of  sugar  in  liver  of  all  animals — Its  percentage — Internal  origin  of 
liver-sugar — Its  production  after  death — Glycogenic  matter  of  the  liver — Its 
properties  and  composition — Absorption  of  liver-sugar  by  hepatic  veins — 
Its  accumulation  in  the  blood  during  digestion — Its  final  decomposition  and 
disappearance      ........     200-207 

CHAPTER    X. 

THE   SPLEEN. 

Capsule  of  Spleen — Variations  in  size  of  the  organ — Its  internal  structure — 
Malpighian  bodies  of  the  spleen — Action  of  spleen  on  the  blood — Effect 
of  its  extirpation  .......     208-212 

CHAPTER    XI. 

THE   BLOOD. 

Red  Globules  of  the  blood — Their  microscopic  characters — Structure  and  com- 
position— Variations  in  size  in  different  animals — White  Globules  of  the  • 
blood — Independence  of  the  two  kinds  of  blood-globules — Plasma — Its  com- 
position— Fibrin — Albumen — Fatty  matters — Saline  ingredients — Extractive 
matters — Coagulation  op  the  Blood — Separation  of  clot  and  serum — Influ- 
ences hastening  or  retarding  coagulation — Coagulation  not  a  commencement 
of  organization — Formation  of  bnffy  coat — Entire  quantity  of  blood  in  body 

213-231 

CHAPTER    XII. 

RESPIRATION. 

Piespiratory  apparatus  of  aquatic  and  air-breathing  animals — Structure  of 
lungs  in  human  subjects — Respiratory  movements  of  chest — Of  glottis — 
Changes  in  the  air  during  respiration — Changes  in  the  blood — Proportions 
of  oxygen  and  carbonic  acid,  in  venous  and  arterial  blood — Solution  of  gases 
by  the  blood-globules — Origin  of  carbonic  acid  in  the  blood — Its  mode  of 
production — Quantity  of  carbonic  acid  exhaled  from  the  body — Variations 
according  to  age,  sex,  temperature,  &c. — Respiration  by  the  skin        .     232-252 


SIV  -  CONTENTS. 

CHAPTER    XIII. 

ANIMAL   HEAT. 

PAGE 

Standard  temperature  of  animals — How  maintained — Production  of  heat  by 
Vegetables — Mode  of  generation  of  animal  heat — Theory  of  combustion — 
Objections  to  this  theory — No  oxidation  in  vegetables  during  production  of 
heat — Quantities  of  oxygen  and  carbonic  acid  in  animals  do  not  correspond 
with  each  other — Production  of  animal  heat  a  local  process — Depends  on. 
the  chemical  phenomena  of  nutrition    .....     253-263 

CHAPTER    XI Y. 

THE   CIRCULATION. 

Circulatory  apparatus  of  fish — Of  reptiles — Of  mammalians — Course  of  blood 
through  the  heart — Action  of  valves — Sounds  of  heart — Movements — Im- 
pulse— Successive  pulsations — Arterial  system — Movement  of  blood  through 
the  arteries — Arterial  pulse — Arterial  pressure — Rapidity  of  arterial  circula- 
tion— The  veins — Causes  of  movement  of  blood  in  the  veins — Rapidity  of 
venous  current — Capillary  circulation — Phenomena  and  causes  of  capillary 
circulation — Rapidity  of  entire  circulation — Local  variations  in  different 
parts        .........     264^306 

CHAPTER    XY. 

IMBIBITION   AND   EXHALATION. — THE   LYMPHATIC    SYSTEM. 

Eudosmosis  and  exosmosis — Mode  of  exhibiting  them — Conditions  which  regu- 
late their  activity — Nature  of  the  membrane — Extent  of  contact — Constitu- 
tion of  the  liquids — Temperature — Pressure  —  Nature  of  eudosmosis  —  Its 
conditions  in  the  living  body — Its  rapidity — Phenomena  of  endosmosis  in 
the  circulation — The  lymphatics — Their  origin — Constitution  of  the  lymph 
and  chyle — Their  quantity — Liquids  secreted  and  reabsorbed  in  twenty- 
four  hours  ........     307-323 

CHAPTER    XYI. 

SECRETION. 

Nature  of  secretion — Variations  in  activity — Mucus — Sebaceous  matter — Its 
varieties — Perspiration — Structure  of  perspiratory  glands — Composition  and 
quantity  of  the  perspiration — Its  use  in  regulating  the  animal  temperature — 
Tears — Milk — Its  acidification — Secretion  of  bile — Anatomical  peculiarities 

324-340 


CONTENTS.  XV 

CHAPTER    XYII. 

EXCRETION. 

PAGE 

Nature  of  excretion — Escrementitious  substances — Effect  of  their  retention — 
Urea — Its  source — Conversion  into  carbonate  of  ammonia — Daily  quantity 
of  urea — Creatine— Creatinine — Urate  of  soda — Urates  of  potassa  and  ammo- 
nia— General  characters  of  the  urine— Its  composition — Variations— Acci- 
dental ingredients  of  the  urine— Acid  and  alkaline  fermentations — Final 
decomposition  of  the  urine  ......  341-364 


SECTION    II. 
NERVOUS    SYSTEM. 

CHAPTER    I. 

GENERAL  CHARACTER  AND   FUNCTIONS   OF   THE   NERVOUS   SYSTEM. 

Nature  of  the  function  performed  by  nervous  system — Two  kinds  of  nervous 
tissue — Fibres  of  white  substance— Their  minute  structure— Division  and 
inosculation  of  nerves — Gray  substance — Nervous  system  of  radiata — Of 
moUusca — Of  articulata — Of  mammalia  and  human  subject — Structure  of 
encephalon — Connections  of  its  different  parts  .        •     .  .     365-887 

CHAPTER    II. 

OF   NERVOUS   IRRITABILITY,  AND   ITS   MODE   OF  ACTION, 

Irritability  of  muscles— How  exhibited— Influences  which  exhaust  and  destroy 
it— Nervous  irritability— How  exhibited— Continues  after  death— Exhausted 
by  repeated  excitement— Influence  of  direct  and  inverse  electrical  currents 
—Nervous  irritability  distinct  from  muscular  irritability— Nature  of  the 
nervous  force— Its  resemblance  to  electricity— Difl'erences  between  the  two 

388-397 

CHAPTER    III. 

THE   SPINAL   CORD. 

Power  of  sensation— Power  of  motion— Distinct  seat  of  sensation  and  motion 
in  nervous  system— Sensibility  and  excitability— Distinct  seat  of  sensibility 
and  excitability  in  spinal  cord— Crossed  action  of  spinal  cord— Independent 
and  associated  action  of  motor  and  sensitive  filaments— Reflex  action  of 
spinal  cord— How  manifested  during  disease— Influence  in  health  on 
sphincters,  voluntary  muscles,  urinary  bladder,  &c.     .  .  .     398-416 


XVI  CONTENTS. 

QHAPTER    IV. 

THE   BRAIN. 

PAGE 

Seat  of  sensibility  and  excitability  in  different  parts  of  the  encephalon — Olfac- 
tory ganglia — Optic  tlxalami— Corpora  striata — Hemispheres — Remarkable 
cases  of  injury  of  hemispheres — Effect  of  their  removal — Imperfect  develop- 
ment in  idiots — Aztec  children — Theory  of  phrenology — Cerebellum — Effect 
of  its  injury  or  removal — Comparative  development  in  different  classes — 
Tuberculaquadrigemina — Tuber  annulare — Medulla  oblongata — Three  kinds 
of  j.'eflex  action  in  nervous  system  .....     417-445 

CHAPTER    Y. 

THE   CRANIAL   NERVES. 

Olfactory  nerves — Optic  nerves — Auditory  nerves — Classification  of  cranial 
nerves — Motor  nerves — Sensitive  nerves — Motor  oculi  communis — Patheti- 
cus — Motor  esternus — Fifth  pair — Its  sensibility — Effect  of  division — Influ- 
ence on  mastication — Influence  on  the  organ  of  sight — Facial  nerve — Effect ' 
of  its  paralysis — Glosso-pharyngeal  nerve — Pneumogastric — Its  distribution 
— Influence  on  pharynx  and  oesophagus—  On  larynx — On  lungs — On  stomach 
and  digestion — Spinal  accessory  nerve — Hypoglossal    .  .  .     446-477 

CHAPTER    VI. 

THE   SPECIAL   SENSES. 

General  and  special  sensibility — Sense  of  touch  in  the  skin  and  mucous  mem- 
branes— Nature  of  the  special  senses — Taste — Apparatus  of  this  sense — Its 
conditions — Its  resemblance  to  ordinary  sensation — Injury  to  the  taste  in 
paralysis  of  the  facial  nerve — Smell — Arrangement  of  nerves  in  nasal  pas- 
sages— Conditions  of  this  sense — Distinction  between  odors  and  irritating 
vapors— Sight— Structure  of  the  eyeball— Special  sensibility  of  the  retina — 
Action  of  the  lens— Of  the  iris— Combined  action  of  two  eyes— Vivid  nature 
of  the  visual  impressions — Heaking — Auditory  apparatus — Action  of  mem- 
brana  tympani — Of  chain  of  bones — Of  their  muscles — Appreciation  of  the 
direction  of  sound — Analogies  of  hearing  with  ordinary  sensation        .  478—513 

CHAPTER    VII. 

SYSTEM   OF   THE   GREAT   SYMPATHETIC. 

Ganglia  of  the  great  sympathetic — Distribution  of  its  nerves — Sensibility  and 
excitability  of  sympathetic— Sluggish  action  of  this  nerve — Influence  over 
organs  of  special  sense — Elevation  of  temperature  after  division  of  sympa- 
thetic— Contraction  of  pupil  following  the  same  operation — Reflex  actions 
taking  place  through  the  great  sympathetic       ....     514-524 


CONTENTS.  XVU 


SECTION    III. 
REPHODUCTION. 

CHAPTER    I. 

ON   THE   NATURE   OF   REPRODUCTION,    AND    THE   ORIGIN   OF   PLANTS  AND 

ANIMALS. 

PAGE 

Nature  and  objects  of  the  function  of  reproduction — Mode  of  its  accomplisli- 
ment — By  generation  from  parents — Spontaneous  generation — Mistaken  in- 
stances of  this  mode  of  generation — Production  of  infusoria — Conditions  of 
their  development — Schultze's  experiment  on  generation  of  infusoria — Pro- 
duction of  animal  and  vegetable  parasites — Encysted  entozoa — Trichina 
spiralis — Tsenia— Cjsticercus — Production  of  taenia  from  cysticercus— Of 
cysticercus  from  eggs  of  taenia — Plants  and  animals  always  produced  by 
generation  from  parents  ......      525-539 

CHAPTER    II. 

ON    SEXUAL  GENERATION   AND   THE   MODE   OF   ITS   ACCOMPLISHMENT. 

Sexual  apparatus  of  plants— Fecundation  of  the  germ— Its  development  into 
a  new  plant — Sexual  apparatus  of  animals— Ovaries  and  testicles — Uni- 
sexual and  bisexual  species— Distinctive  characters  of  the  two  sexes       540-543 

CHAPTER    III. 

ON  THE  EGG,  AND  THE  FEMALE  ORGANS  OF  GENERATION. 

Size  and  appearance  of  the  egg— Vitelline  membrane— Vitellus—Germinative 
vesicle— Germinative  spot — Ovaries — Graafian  follicles — Oviducts — Female 
generative  organs  of  frog — Ovary  and  oviduct  of  fowl— Changes  in  the  egg, 
while  passing  through  the  oviduct— Complete  fowl's  egg— Uterus  and  ova- 
ries of  the  sow — Female  generative  apparatus  of  the  human  subject — Fal- 
lopian tubes— Body  of  the  uterus— Cervix  of  the  uterus         .  .     544-555 

CHAPTER    lY. 

ON   THE   SPERMATIC   FLUID,    AND   THE   MALE   ORGANS   OF   GENERATION. 

The  spermatozoa— Their  varieties  in  different  species — Their  movement — For- 
mation of  spermatozoa  in  the  testicles— Accessory  male  organs  of  generation 
—  Epididymis  —  Vas  deferens  —  Vesiculae  seminales  —  Prostate — Cowper's 
glanda— Function  of  spermatozoa— Physical  conditions  of  fecundation     556-562 

2 


XVlll  CONTENTS. 


CHAPTER    Y. 

ON   PERIODICAL   OVULATION,    AND   THE   FUNCTION   OP   MENSTRUATION. 

PAGE 

Periodical  Ovulation — Pre-existence  of  eggs  in  the  ovaries  of  all  animals — 
Their  increased  development  at  the  period  of  puberty — Their  successive 
ripening  and  periodical  discharge — Discharge  of  eggs  independently  of  sexual 
intercourse — Rupture  of  Graafian  follicle,  and  expulsion  of  the  egg — Pheno- 
mena of  cestruation — Menstruation — Correspondence  of  menstrual  periods 
with  periods  of  ovulation  in  the  lower  animals — Discharge  of  egg  during 
menstrual  period — Conditions  of  its  impregnation,  after  leaving  the  ovary 

563-575 

CHAPTER    VI. 

ON  THE   CORPUS  LUTEUM  OP  MENSTRUATION  AND  PREGNANCY. 

Corpus  Luteum  of  Menstruation — Discharge  of  blood  into  the  ruptured  Graafian 
follicle — Decolorization  of  the  clot,  and  hypertrophy  of  the  membrane  of  the 
vesicle — Corpus  luteum  of  menstruation,  at  the  end  of  three  weeks — Yellow 
coloration  of  convoluted  wall — Corpus  luteum  of  menstruation  at  the  end 
of  four  weeks — Shrivelling  and  condensation  of  its  tissues — Its  condition  at 
the  end  of  nine  weeks — Its  final  atrophy  and  disappearance — Corpus  Luteum 
OF  Pregnancy — Its  continued  development  after  the  third  week — Appearance 
at  the  end  of  second  month — Of  fourth  month — At  the  termination  of  preg- 
nancy— Its  atrophy  and  disappearance  after  delivery — Distinctive  characters 
of  corpora  lutea  of  menstruation  and  pregnancy  .  .  .     576-585 

CHAPTER    YII. 

ON  THE  DEVELOPMENT  OP  THE  IMPREGNATED  EGG. 

Segmentation  of  the  vitellus — Formatioh  of  blastodermic  membrane — Two 
layers  of  blastodermic  membrane — Thickening  of  external  layer — Formation 
of  primitive  trace — Dorsal  plates — Abdominal  plates — Closure  of  dorsal  and 
abdominal  plates  on  the  median  line — Formation  of  intestine — Of  mouth 
and  anus — Of  organs  of  locomotion — Continued  development  of  organs,  after 
leaving  the  egg    ........    586-595 

CHAPTER    YIII. 

THE   UMBILICAL  VESICLE. 

Separation  of  vitelline  sac  into  two  cavities — Closure  of  abdominal  walls,  and 
formation  of  umbilical  vesicle  in  fish — Mode  of  its  disappearance  after  hatch- 
ing— Umbilical  vesicle  in  human  embryo — Formation  and  growth  of  pedicle 
— Disappearance  of  umbilical  vesicle  during  embryonic  life  .  .       596-598 


CONTEXTS.  XIX 

CHAPTER    IX. 

AMNION  AND  ALLANT0I8 — DEVELOPMENT  OF  THE  CHICK. 

PAGE 

Necessity  for  accessory  organs  in  the  development  of  birds  and  quadrupeds — 
Formation  of  amniotic  folds — Their  union  and  adhesion — Growth  of  allantois 
from  lower  part  of  intestine — Its  vascularity — Allantois  in  the  egg  of  the 
fowl — Respiration  of  the  egg — Absorption  of  calcareous  matter  from  the 
shell — Ossification  of  skeleton — Fracture  of  egg-shell — Casting  off  of  amnion 
and  allantois       ........     599-607 

CHAPTER    X. 

DEVELOPMENT  OF  THE  EGG  IN  THE  HUMAN  SPECIES FORMATION  OF  THE 

CHORION. 

Conversion  of  allantois  into  chorion — Subsequent  changes  of  the  chorion — 
Its  villosities — Formation  of  bloodvessels  in  villosities — Action  of  villi  of 
chorion  in  providing  for  nutrition  of  foetus — Proofs  that  the  chorion  is  formed 
from  the  allantois  —  Partial  disappearance  of  villosities  of  chorion,  and 
changes  in  its  external  surface  ......     608-613 

CHAPTER    XI. 

DEVELOPMENT  OF  UTERINE  MUCOUS  MEMBRANE FORMATION  OF  THE 

DECIDUA. 

Structure  of  uterine  mucous  membrane — Uterine  tubules — Thickening  of  ute- 
rine mucous  membrane  after  impregnation — Decidua  vera — Entrance  of  egg 
into  uterus — Decidua  reflexa — Inclosure  of  egg  by  decidua  reflexa — Union 
of  chorion  with  decidua — Changes  in  the  relative  development  of  different 
portions  of  chorion  and  decidua  .....     614-620 

CHAPTER    XII. 

THE  PLACENTA. 

Nourishment  of  foetus  by  maternal  and  foetal  vessels — Arrangement  of  the 
vascular  membranes  in  different  species  of  animals — Membranes  of  foetal 
pig — Cotyledon  of  cow's  uterus — Development  of  foetal  tufts  in  human  pla- 
centa— Development  of  uterine  sinuses — Relation  of  foetal  and  maternal ' 
bloodvessels  in  the  placenta  —  Proofs  that  the  maternal  sinuses  extend 
through  the  whole  thickness  of  the  placenta — Absorption  and  exhalation 
by  the  placental  vessels  ......     621-629 


XX  CONTENTS. 

CHAPTER    XIII 

DISCHARGE  OF  THE  OVUM,  AND  INVOLUTION  OF  THE  UTERUS. 

PAGE 

Enlargement  of  amniotic  cavity — Contact  of  amnion  and  chorion — Amniotic 
fluid — Movements  of  foetus — Union  of  decidua  vera  and  reflexa — Expulsion 
of  the  ovum  and  discharge  of  decidual  membrane — Separation  of  the  pla- 
centa— Formation  of  new  mucous  membrane  underneath  the  old  decidua — 
Fatty  degeneration  and  reconstruction  of  muscular  walls  of  uterus         630-636 

CHAPTER    XIY. 

DEVELOPMENT  OF  THE  EMBRYO — NERVOUS  SYSTEM,  ORGANS  OF  SENSE, 
SKELETON  AND  LIMBS. 

Formation  of  spinal  cord  and  cerebro-spinal  axis — Tbree  cerebral  vesicles — 
Hemispheres — Optic  thalami — Tubercula  quadrigemina — Cerebellum — Me- 
dulla oblongata — Eye — Pupillary  membrane — Skeleton — Chorda  dorsalis — 
Bodies  of  the  vertebrae — Laminse  and  ribs — Spina  bifida — Anterior  and  pos- 
terior extremities — Tail — Integument — Hair — Vernix  caseosa — Exfoliation 
of  epidermis        ........     637-643 

CHAPTER    XV. 

DEVELOPMENT  OF  THE  ALIMENTARY  CANAL  AND  ITS  APPENDAGES. 

Formation  of  intestine — Stomach — Duodenum — Convolutions  of  intestine — 
Large  and  small  intestine — Caput  coli  and  appendix  vermiformis — Umbi- 
lical hernia — Formation  of  urinary  bladder — Urachus — Vesico- rectal  septum 
— Perineum — Liver — Secretion  of  bile — Gastric  juice — Meconium — Glyco- 
genic function  of  liver — Diabetes  of  foetus — Pharynx  and  oesophagus — Dia- 
phragm— Diaphragmatic  hernia — Heart  and  pericardium — Ectopia  cordis — 
Development  of  the  face  ......     644-654 

CHAPTER    XYI. 

DEVELOPMENT  OP  THE  KIDNEYS,  WOLFFIAN   BODIES,  AND  INTERNAL  ORGANS 

OF  GENERATION. 

Wolffian  bodies — Their  structure — First  appearance  of  kidneys — Growth  of 
kidneys,  and  atrophy  of  Wolffian  bodies — Testicles  and  ovaries — Descent  of 
the  testicles — Tunica  vaginalis  testis — Congenital  inguinal  hernia — Descent 
of  the  ovaries — Development  of  the  uterus       ....     655-664 


CONTEXTS.  XXI 

CHAPTER    XYI  I. 

DEVELOPMENT  OF  THE  CIRCULATORY  APPARATUS. 

PAGE 

First,  or  vitelline   circulation— Area   vasculosa — Sinus  terminalis— Vitelline 

circulation  of  fish — Arrangement  of  arteries  and  veins  in  body  of  foetus 

Second,  or  placental  circulation — Omphalo-mesenteric  arteries  and  vein 

Circulation  of  the  umbilical  vesicle— Of  the  allantois  and  placenta— Umbi- 
lical arteries  and  veins — Third,  or  adult  circulation— Portal  and  pulmonary 
syatems — Development  of  the  arterial  system— Development  of  the  venous 
system — Changes  in  the  hepatic  circulation — Portal  vein — Umbilical  vein 
— Ductus  venosus — Changes  in  the  cardiac  circulation — Division  of  heart 
into  right  and  left  cavities — Aorta  and  pulmonary  artery — Ductus  arteriosus 
— Foramen  ovale  and  Eustachian  valve  —  Changes  in  circulation  at  the 
period  of  birth 665-68(5 

CPI  AFTER    XYI  1 1. 

DEVELOPMENT  OF  THE  BODY  AFTER  BIRTH. 

Condition  of  foetus  at  birth- Gradual  establishment  of  respiration — Inactivity 
of  the  animal  functions —  Preponderance  of  reflex  actions  in  the  nervous 
system — peculiarities  in  the  action  of  drugs  on  infant — Difference  in  relative 
size  of  organs,  in  infant  and  adult— Withering  and  separation  of  umbilical 
cord- Exfoliation  of  epidermis— First  and  second  sets  of  teeth— Subsequent 
changes  in  osseous,  muscular  and  tegumentary  systems,  and  general  devel- 
opment of  the  body 687-690 


LIST  OF  ILLUSTEATIOXS, 

ALL  OF  WHICH    HAVE    BEEN  PREPARED  FROM  ORIGINAL   DRAWINGS,  WITH  THE 
EXCEPTION  OF  TEN,  CREDITED  TO  THEIR  AUTHORITIES. 


FIG. 

1.  Fibula  tied  in  a  knot,  after  maceration  in  a  dilute  acid 

2.  Grains  of  potato  starch     . 

3.  Starch  grains  of  Bermuda  arrowroot 

4.  Starch  grains  of  wheat  flour 

5.  Starch  grains  of  Indian  coi'n 

6.  Starch  grains  from  wall  of  lateral  ventricle 

7.  Stearine 

8.  Oleaginous  principles  of  human  fat 

9.  Human  adipose  tissue 

10.  Chyle 

11.  Globules  of  cow's,  milk 

12.  Cells  of  costal  cartilages 

13.  Hepatic  cells 

14.  Uriniferous  tubules  of  dog 

15.  Muscular  fibres  of  human  uterus 

16.  Alimentary  canal  of  fowl 

17.  Compound  stomach  of  ox 

18.  Human  alimentary  canal 

19.  Skull  of  rattlesnake  .  .  .  Prom 

20.  Skull  of  polar  bear 

21.  Skull  of  the  horse 

22.  Molar  tooth  of  the  horse 

23.  Human  teeth — upper  jaw 

24.  Buccal  and  glandular  epithelium  deposited  from  saliva 

25.  Gastric  mucous  membrane,  viewed  from  above    . 

26.  Gastric  mucous  membrane,  in  vertical  section     . 

27.  Mucous  membrane  of  pig's  stomach 

28.  Gastric  tubules  from  pig's  stomach,  pyloric  portion 

29.  Gastric  tubules  from  pig's  stomach,  cardiac  portion 

30.  Confervoid  vegetable,  growing  in  gastric  juice     . 

31.  Follicles  of  Lieberkiihn     .... 

32.  Brunner's  duodenal  glands 

33.  Contents  of  stomach,  during  digestion  of  meat    . 

34.  From  duodenum  of  dog,  during  digestion  of  meat 

35.  From  middle  of  small  intestine    .  . 


From  Rymer  Jone; 
Achille-Richard 


PAGE 

75 

80 

80 

81 

81 

82 

87 

88 

90 

90 

91 

91 

92 

92 

93 

117 

118 

119 

121 

122 

122 

122 

123 

124 

133 

133 

134 

134 

134 

140 

151 

152 

158 

158 

159 


iii) 


XXIV 


LIST    OF    ILLUSTRATIONS. 


FIG. 

36.  From  last  quarter  of  small  intestine 

37.  One  of  the  closed  follicles  of  Peyer's  patches 

38.  Glandulae  agminatse 

39.  Extremity  of  intestinal  villus 

40.  Panizza's  experiment  on  absorption  by  bloodvessels 

41.  Chyle,  from  commencement  of  thoracic  duct 

42.  Lacteals,  thoracic  duct,  &c. 

43.  Lacteals  and  lymphatics  . 

44.  Intestinal  epithelium,  in  intervals  of  digestion 

45.  Intestinal  epithelium,  during  digestion    . 

46.  Cholesterin  .... 

47.  Ox-bile,  crystallized 

48.  Glyko-cholate  of  soda  from  ox-bile 

49.  Glyko-cholate  and  tauro-cholate  of  soda,  from  ox-bile 

50.  Dog's  bile,  crystallized 

51.  Human  bile,  showing  resinous  matters 

52.  Crystalline  and  resinous  biliary  substances,  from  dog's  intestine 

53.  Duodenal  fistula    .... 
64.  Human  blood-globules 

55.  The  same,  seen  out  of  focus 

56.  The  same,  seen  within  the  focus  . 

57.  The  same,  adhering  together  in  rows 

58.  The  same,  swollen  by  addition  of  water 

59.  The  same,  shrivelled  by  evaporation 
GO.  Blood-globules  of  frog 

61.  White  globules  of  the  blood 

62.  Coagulated  fibrin   .... 

63.  Coagulated  blood  .... 

64.  Coagulated  blood,  after  separation  of  clot  and  serum 

65.  Recent  coagulum   .... 

66.  Coagulated  blood,  clot  buffed  and  cupped 

67.  Head  and  gills  of  menobranchus  . 

68.  Lung  of  frog  .... 

69.  Human  larynx,  trachea,  bronchi,  and  lungs 
7J.  Single  lobule  of  human  lung 

71.  Diagram  illustrating  the  respiratory  movements 

72.  Small  bronchial  tube 

73.  Human  larynx,  with  glottis  closed 

74.  The  same,  with  glottis  open 

75.  Human  larynx — posterior  view    . 

76.  Circulation  of  fish 

77.  Circulation  of  reptiles 

78.  Circulation  of  mammalians 

79.  Human  heart,  anterior  view 

80.  Human  heart,  posterior  view 

81.  Right  auricle  and  ventricle,  tricuspid  valve  open,  arterial  valves  closed 

82.  Right  auricle  and  ventricle,  tricuspid  valve  closed,  arterial  valves  open 

83.  Course  of  blood  through  the  heart 

84.  Illustrating  production  of  valvular  sounds 

85.  Heart  of  frog,  in  relaxation 


PAGE 

159 
162 
162 
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165 
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168 
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172 
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177 
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182 
183 
189 
190 
214 
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226 
22T 
230 
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233 
234 
235 
235 
237 
239 
240 
240 
241 
265 
266 
267 
268 
268 
268 
269 
270 
273 
276 


LIST    OF    ILLUSTRATIONS. 


XXV 


FIG. 

86. 
87. 


90. 

91. 

92. 

93. 

94. 

95. 

96. 

97. 

98. 

99. 
100. 
101. 
102. 
103. 
104. 
105. 
106. 
107. 
108. 
109. 
110. 
111. 
112. 
113. 
114. 
115. 
116. 
117. 
118. 
119. 
120. 
121. 
122. 
123. 
124. 
125. 
126. 
127. 
128. 
129. 
130. 
131. 
132. 
133. 
134. 
135. 


Heart  of  frog,  iu  contraction       . 

Simple  looped  fibres         .... 

Bullock's  heart,  showing  superficial  muscular  fibres 

Left  ventricle  of  bullock's  heart,  showing  deep  fibres 

Diagram  of  circular  fibres  of  the  heart 

Converging  fibres  of  the  apex  of  the  heart 

Artery  in  pulsation 

Curves  of  the  arterial  pulsation 

Volkmann's  apparatus    . 

The  same  .... 

Vein,  with  valves  open    . 

Vein,  with  valves  closed 

Small  artery,  with  capillary  branches    . 

Capillary  network 

Capillary  circulation 

Diagram  of  the  circulation 

Follicles  of  a  compound  mucous  glandule 

Meibomian  glands 

Perspiratory  gland 

Glandular  structure  of  mamma 

Colostrum  corpuscles 

Milk-globules      .... 

Division  of  portal  vein  in  liver 

Lobule  of  liver 

Hepatic  cells        .... 

Urea         .  '  . 

Creatine 

Creatinine 

Urate  of  soda 

Uric  acid 

Oxalate  of  lime    . 

Phosphate  of  magnesia  and  ammonia 

Nervous  filaments,  from  brain     . 

Nervous  filaments  from  sciatic  nerve 

Division  of  a  nerve 

Inosculation  of  nerves 

Nerve  cells 

Nervous  system  of  starfish 

Nervous  system  of  aplysia 

Nervous  system  of  centipede 

Cerebro-spinal  system  of  man     . 

Spinal  cord 

Brain  of  alligator 

Brain  of  rabbit 

Medulla  oblongata  of  human  brain 

Diagram  of  human  brain 

Experiment  showing  irritability  of  muse 

Experiment  showing  irritability  of  nerve 

Action  of  direct  and  inverse  currents 

Diagram  of  spinal  cord  and  nerves 


From  KoUiker 

From  Ludovic 

From  Todd  and  Bowman 


From  Lehmann  (Funke's  Atlas) 
From  Lehmann  (Funke's  Atlas) 
From  Lehmann  (Funke's  Atlas) 


les 


XXVI 


LIST    OF    ILLUSTRATIONS. 


FIG. 

136.  Spinal  cord  in  vertical  section 

137.  Experiment,  showing  effect  of  poisons  upon  nerves 

138.  Pigeon,  after  removal  of  the  hemispheres 

139.  Aztec  children 

140.  Brain  in  situ         .... 

141.  Transverse  section  of  brain  .  . 

142.  Pigeon,  after  removal  of  the  cerebellum 

143.  Brain  of  healthy  pigeon  in  profile 

144.  Brain  of  operated  pigeon  in  profile 

145.  Brain  of  healthy  pigeon,  posterior  view 

146.  Brain  of  operated  pigeon,  posterior  view 

147.  Inferior  surface  of  brain  of  cod 

148.  Inferior  surface  of  brain  of  fowl  . 

149.  Course  of  optic  nerves  in  man     . 

150.  Distribution  of  fifth  nerve  upon  the  face 

151.  Facial  nerve 

152.  Pneumogastric  nerve       . 

153.  Diagram  of  tongue 

154.  Distribution  of  nerves  in  the  nasal  passages 

155.  Vertical  section  of  eyeball 

156.  Dispersion  of  rays  of  light 

157.  Action  of  crystalline  lens 

158.  Myopia     . 

159.  Presbyopia 

160.  Vision  at  short  distance 

161.  Vision  at  long  distance   . 

162.  Refraction  of  lateral  rays 

163.  Skull,  as  seen  by  left  eye 

164.  Skull,  as  seen  by  right  eye  . 

165.  Human  auditory  apparatus 

166.  Great  sympathetic 

167.  Cat,  after  division  of  sympathetic  in  the  neck 

168.  Different  kinds  of  infusoria 

169.  Experiment  on  spontaneous  generation 

170.  Trichina  spiralis 

171.  Taenia      .... 

172.  Cysticercus,  retracted 

173.  Cysticercus,  unfolded 

174.  Blossom  of  Convolvulus  purpureus 

175.  Single  articulation  of  Taenia  crassicoUis 

176.  Human  ovum 

177.  Human  ovum,  ruptured  by  pressure 

178.  Female  generative  organs  of  frog 

179.  Mature  frogs'  eggs 

180.  Female  generative  organs  of  fowl 

181.  Fowl's  egg 

182.  Uterus  and  ovaries  of  the  sow     . 

183.  Generative  organs  of  human  female 

184.  Spermatozoa 

185.  Graafian  follicle  .     . 


From 


Schultze 


PAGE 

409 
412 
421 
426 
428 
429 
431 
433 
433 
433 
433 
436 
436 
437 
452 
457 
462 
483 
489 
493 
495 
495 
496 
496 
497 
497 
600 
502 
502 
507 
515 
522 
530 
532 
535 
536 
537 
537 
540 
541 
544 
545 
547 
548 
551 
552 
553 
554 
557 
56S 


LIST    OF    ILLUSTRATIONS. 


XXVll 


FIG.  PAGE 

186.  Ovary  with  Graafian  follicle  ruptured     .  .  .  .  .568 

187.  Graafian  follicle,  ruptured  and  filled  with  blood             .             .             .  577 

188.  Corpus  luteum,  three  weeks  after  menstruation             .             .             .  578 

189.  Corpus  luteum,  four  weeks  after  menstruation              .             .             .  579 

190.  Corpus  luteum,  nine  weeks  after  menstruation              .            .             .  579 

191.  Corpus  luteum  of  pregnancy,  at  end  of  second  month  .             .             .  582 

192.  Corpus  luteum  of  pregnancy,  at  end  of  fourth  mouth    .             .             .  582 

193.  Corpus  luteum  of  pregnancy,  at  term     .....  583 

194.  Segmentation  of  the  vitellus      ......  587 

195.  Impregnated  egg,  showing  embryonic  spot         .  .  .  .590 

196.  Impregnated  egg,  showing  two  layers  of  blastodermic  membrane          .  591 

197.  Impregnated  egg,  farther  advanced        .....  591 

198.  Frog's  egg,  at  an  early  period     ......  592 

199.  Egg  of  frog,  in  process  of  development   .....  592 

200.  Egg  of  frog,  farther  advanced      ......  592 

201.  Tadpole,  fully  developed  .  .  .  .  .  .593 

202.  Tadpole,  changing  into  frog         .             .             .             .             .             .  594 

203.  Perfect  frog  .  .  .  .  .  .  .  .594 

204.  Egg  of  fish           .             .             .             .             .             .             .             .  596 

205.  Young  fish,  with  umbilical  vesicle          .....  597 

206.  Human  embryo,  with  umbilical  vesicle              ....  597 

207.  Fecundated  egg,  showing  formation  of  amnion  ....  600 

208.  Fecundated  egg,  showing  commencement  of  allantois  .             .             .  601 

209.  Fecundated  egg,  with  allantois  nearly  complete             .             .             .  601 

210.  Fecundated  egg,  with  allantois  fully  formed       ....  602 

211.  Egg  of  fowl,  showing  area  vasculosa       .....  603 

212.  Egg  of  fowl,  showing  allantois,  amnion,  &c.       .             •            .             .  604 

213.  Human  ovum,  showing  formation  of  chorion      ....  608 

214.  Compound  villosity  of  human  chorion                 ....  610 

215.  Extremity  of  villosity  of  chorion            .....  611 

216.  Human  ovum,  at  end  of  third  month     .  .  .  .  .612 

217.  Uterine  mucous  membrane         ......  615 

218.  Uterine  tubules   .  .  .  .  .  .  .  .615 

219.  Impregnated  uterus^  showing  formation  of  decidua       .             .             .  617 

220.  Impregnated  uterus,  showing  formation  of  decidua  reflexa       .             .  617 

221.  Impregnated  uterus,  with  decidua  reflexa  complete       .             .             .  617 

222.  Impregnated  uterus,  showing  union  of  chorion  and  decidua    .             .  619 

223.  Pregnant  uterus,  showing  formation  of  placenta            .             .             .  620 

224.  Foetal  pig,  with  membranes         ......  622 

225.  Cotyledon  of  cow's  uterus           ......  622 

226.  Extremity  of  foetal  tuft,  human  placenta           ....  624 

227.  Fcetal  tuft  of  human  placenta  injected               ....  625 

228.  Vertical  section  of  placenta        ......  626 

229.  Human  ovum,  at  end  of  first  month        .....  630 

230.  Human  ovum,  at  end  of  third  month    .....  631 

231.  Gravid  human  uterus  and  contents        .....  632 

232.  Muscular  fibres  of  unimpregnated  uterus           ....  635 

233.  Muscular  fibres  of  human  uterus,  ten  days  after  parturition     .             .  635 

234.  Muscular  fibres  of  human  uterus,  three  weeks  after  parturition            .  636 

235.  Formation  of  cerebro-spinal  axis            .....  637 


XSVlll 


LIST    OF    ILLUSTRATIONS. 


FIG. 

236.  Formation  of  cerebro-spinal  axis 

237.  Foetal  pig,  sliowing  brain  and  spinal  cord 

238.  Foetal  pig,  sliowing  brain  and  spinal  cord 

239.  Head  of  foetal  pig  .  .  . 

240.  Brain  of  adult  pig 

241.  Formation  of  alimentary  canal  . 

242.  Foetal  pig,  showing  umbilical  hernia 

243.  Head  of  human  embryo,  at  twenty  days  .  .     From 

244.  Head  of  human  embryo,  at  end  of  sixth  week 

245.  Head  of  human  embryo,  at  end  of  second  month 

246.  Foetal  pig,  showing  Wolffian  bodies 

247.  Fcetal  pig,  showing  first  appearance  of  kidneys 

248.  Internal  organs  of  generation 

249.  Internal  organs  of  generation     . 

250.  Formation  of  tunica  vaginalis  testis 

251.  Congenital  inguinal  hernia 

252.  Egg  of  fowl,  showing  area  vasculosa 

253.  Egg  of  fish,  showing  vitelline  circulation 

254.  Young  embryo  and  its  vessels     . 

255.  Embryo  and  its  vessels,  farther  advanced 

256.  Arterial  system,  embryonic  form 

257.  Arterial  system,  adult  form 

258.  Early  condition  of  venous  system 

259.  Venous  system,  farther  advanced 

260.  Continued  development  of  venous  system 

261.  Adult  condition  of  venous  system 

262.  Early  form  of  hepatic  circulation 

263.  Hepatic  circulation  farther  advanced     . 

264.  Hepatic  circulation,  during  latter  part  of  foetal  life 

265.  Adult  form  of  hepatic  circulation 

266.  Foetal  heart 

267.  Foetal  heart 

268.  Fcetal  heart 

269.  Foetal  heart 

270.  Heart  of  infant    . 

271.  Heart  of  human  foetus,  showing  Eustachian  valve 

272.  Circulation  through  the  foetal  heart 

273.  Adult  circulation  through  the  heart 


Lonstet 


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HUMAN   PHYSIOLOGY. 


INTRODUCTION. 

I.  Physiology  is  the  study  of  the  phenomena  presented  by 
organized  bodies,  animal  and  vegetable. 

These  phenomena  are  different  from  those  presented  by  inorganic 
substances.  They  require,  for  their  production,  the  existence  of 
peculiarly  formed  animal  and  vegetable  organisms,  as  well  as  the 
presence  of  various  external  conditions,  such  as  warmth,  light,  air, 
moisture,  &c. 

They  are  accordingly  more  complicated  than  the  phenomena  of 
the  inorganic  world,  and  require  for  their  study,  not  only  a  pre- 
vious acquaintance  with  the  laws  of  chemistry  and  physics,  but,  in 
addition,  a  careful  examination  of  other  characters  which  are  pecu- 
liar to  them. 

These  peculiar  phenomena,  by  which  we  so  readily  distinguish 
living  organisms  from  inanimate  substances,  are  called  Vital  pheno- 
mena, or  the  phenomena  of  Life.  Physiology  consequently  includes 
the  study  of  all  these  phenomena,  in  whatever  order  or  species  of 
organized  body  they  may  originate. 

We  find,  however,  upon  examination,  that  there  are  certain 
general  characters  by  which  the  vital  phenomena  of  vegetables 
resemble  each  other,  and  by  which  they  are  distinguished  from  the 
vital  phenomena  of  animals.  Thus,  vegetables  absorb  carbonio 
acid,  and  exhale  oxygen;  animals  absorb  oxygen,  and  exhale  car- 
bonic acid.  Vegetables  nourish  themselves  by  the  absorption  of 
unorganized  liquids  and  gases,  as  water,  ammonia,  saline  solutions, 
&c. ;  animals  require  for  their  support  animal  or  vegetable  sub- 
stances as  food,  such  as  meat,  fruits,  milk,  &c.  Physiology,  then, 
4  (  49  ) 


50  INTRODUCTION. 

is  naturally  divided  into  two  parts,  viz.,  Vegetable  Physiology,  and 
Animal  Physiology. 

Again,  the  different  groups  and  species  of  animals,  while  they 
resemble  each  other  in  their  general  characters,  are  distinguished 
by  certain  minor  differences,  both  of  structure  and  function,  which 
require  a  special  study.  Thus,  the  physiology  of  fishes  is  not 
exactly  the  same  with  that  of  reptiles,  nor  the  physiology  of  birds 
with  that  of  quadrupeds.  Among  the  warm-blooded  quadrupeds, 
the  carnivoTa  absorb  more  oxygen,  in  proportion  to  the  carbonic 
acid  exhaled,  than  the  herbivora.  Among  the  herbivorous  quad- 
rupeds, the  process  of  digestion  is  comparatively  simple  in  the 
horse,  while  it  is  complicated  in  the  ox,  and  other  ruminating  ani- 
mals. There  is,  therefore,  a  special  physiology  for  every  distinct 
species  of  animal. 

Human  Physiology  treats  of  the  vital  phenomena  of  the  human 
species.  It  is  more  practically  important  than  the  physiology  of 
the  lower  animals,  owing  to  its  connection  with  human  pathology 
and  therapeutics.  But  it  cannot  be  made  the  exclusive  subject  of 
our  study ;  for  the  special  physiology  of  the  human  body  cannot 
be  properly  understood  without  a  previous  acquaintance  with  the 
vital  phenomena  common  to  all  animals,  and  to  all  vegetables; 
beside  which,  there  are  many  physiological  questions  that  require 
for  their  solution  experiments  and  observations,  which  can  only  be 
made  upon  the  lower  animals. 

While  the  following  treatise,  therefore,  has  for  its  principal  sub- 
ject the  study  of  Human  Physiology,  this  will  be  illustrated,  when- 
ever it  may  be  required,  by  what  we  know  in  regard  to  the  vital 
phenomena  of  vegetables  and  of  the  lower  animals. 

II.  Since  Physiology  is  the  study  of  the  active  phenomena  of 
living  bodies,  it  requires  a  previous  acquaintance  with  their  struc- 
ture, and  with  the  substances  of  which  they  are  composed ;  that  is, 
with  their  anatomy. 

Anatomy,  again,  requires  a  previous  acquaintance  with  inorganic 
substances ;  since  some  of  these  inorganic  substances  enter  into  the 
composition  of  the  body.  Chloride  of  sodium,  for  example,  water, 
and  phosphate  of  lime,  are  component  parts  of  the  animal  frame, 
and  therefore  require  to  be  studied  as  such  by  the  anatomist. 
Now  these  inorganic  substances,  when  placed  under  the  requisite 
external  conditions,  present  certain  active  phenomena,  which  are 
characteristic  of  them,  and  by  which  they  may  be   recognized. 


INTRODUCTION.  51 

Thus  lime,  dissolved  in  water,  if  brought  into  contact  with  car- 
bonic acid,  alters  its  condition,  and  takes  part  in  the  formation  of 
an  insoluble  substance,  carbonate  of  lime,  which  is  thrown  down 
as  a  deposit.  A  knowledge  of  such  chemical  reactions  as  these  is 
necessary  to  the  anatomist,  since  it  is  by  them  that  he  is  enabled  to 
recognize  the  inorganic  substances,  forming  a  part  of  the  animal 
body. 

It  is  important  to  observe,  however,  that  a  knowledge  of  these 
reactions  is  necessary  to  the  anatomist  only  in  order  to  enable  him 
to  judge  of  the  presence  or  absence  of  the  inorganic  substances  to 
which  they  belong.  It  is  the  object  of  the  anatomist  to  make  him- 
self acquainted  with  every  constituent  part  of  the  body.  Those 
parts,  therefore,  which  cannot  be  recognized  by  their  form  and 
texture,  he  distinguishes  by  their  chemical  reactions.  But  after- 
ward, he  has  no  occasion  to  decompose  them  further,  or  to  make 
them  enter  into  new  combinations ;  for  he  only  wishes  to  know 
these  substances  as  they  exist  in  the  body,  and  not  as  they  may  exist 
under  other  conditions. 

The  unorganized  substances  which  exist  in  the  body  as  compo- 
nent parts  of  its  structure,  such  as  chloride  of  sodium,  water,  phos- 
phate of  lime,  &c.,  are  called  X}xe  proximate  ;principles  of  the  body. 
Mingled  together  in  certain  proportions,  they  make  up  the  animal 
fluids,  and  associated  also  in  a  solid  form,  they  constitute  the  tissues 
and  organs,  and  in  this  way  make  up  the  entire  frame. 

Anatomy  makes  us  acquainted  with  all  these  component  parts  of 
the  body,  both  solid  and  fluid.  It  teaches  us  the  structure  of  the 
body  in  a  state  of  rest ;  that  is,  just  as  it  would  be  after  life  had 
suddenly  ceased,  and  before  putrefaction  had  begun.  On  the  other 
hand.  Physiology  is  a  description  of  the  body  in  a  state  of  activity. 
It  shows  us  its  movements,  its  growth,  its  reproduction,  and  the 
chemical  changes  which  go  on  in  its  interior ;  and  in  order  to  com- 
prehend these,  we  must  know,  beforehand,  its  entire  mechanical, 
textural,  and  chemical  structure. 

It  is  evident,  therefore,  that  the  description  of  the  proximate  prin- 
ciples, or  the  chemical  substances  entering  into  the  constitution  of 
the  body,  is,  strictly  speaking,  a  part  of  Anatomy.  But  there  are 
many  reasons  why  this  study  is  more  conveniently  pursued  in  con- 
nection with  Physiology ;  for  some  of  the  proximate  principles  are 
derived  directly,  as  we  shall  hereafter  show,  from  the  external  world, 
and  some  are  formed  from  the  elements  of  the  food  in  the  process 
of  digestion ;  while  most  of  them  undergo  certain  changes  in  the 


52  INTEODUCTION". 

interior  of  the  body,  which  result  in  the  formation  of  new  sub- 
stances ;  all  these  active  phenomena  belonging  necessarily  to  the 
domain  of  Physiology. 

The  description  of  the  proximate  principles  of  animals  and  vege- 
tables will  therefore  be  introduced  into  the  following  pages. 

The  description  of  the  minute  structures  of  the  body,  or  Micro- 
scopic Anatomy,  is  also  so  closely  connected  with  some  parts  of  Phy- 
siology as  to  make  it  convenient  to  speak  of  them  together ;  and 
this  will  accordingly  be  done,  whenever  the  nature  of  the  subject 
may  make  it  desirable. 

III.  The  study  of  Physiology,  like  that  of  all  the  other  natural 
sciences,  is  a  study  of  -plienomena,  and  of  phenomena  alone.  The 
essential  nature  of  the  vital  processes,  and  their  ultimate  causes, 
are  questions  which  are  beyond  the  reach  of  the  physiologist,  and 
cannot  be  determined  by  the  means  of  investigation  which  are  at 
his  disposal. 

Consequently,  all  efforts'  to  solve  them  will  only  serve  to  mislead 
the  investigator,  and  to  distract  his  attention  from  the  real  subject 
of  examination.  Much  time  has  been  lost,  for  example,  in  discuss- 
ing the  probable  reason  why  menstruation  returns,  in  the  human 
female,  at  the  end  of  every  four  weeks.  But  the  observation  of 
nature,  which  is  our  only  means  of  scientific  investigation,  cannot 
throw  any  light  on  this  point,  but  only  shows  us  the  fact  that  men- 
struation docs  really  occur  at  the  above  periods,  together  with  the 
phenomena  which  accompany  it,  and  the  conditions  under  which  it 
is  hastened  or  retarded,  and  increased  or  diminished,  in  intensity, 
duration,  &c.  If  we  employ  ourselves,  consequently,  in  the  discus- 
sion of  the  reason  above  mentioned,  we  shall  only  become  involved 
in  a  network  of  hypothetical  surmises,  which  can  never  lead  to  any 
definite  result.  Our  time,  therefore,  will  be  much  more  profitably 
devoted  to  the  study  of  the  above  phenomena,  which  can  be  learned 
from  nature,  and  which  constitute  afterward,  a  permanent  acquisi- 
tion. 

The  physiologist,  accordingly,  confines  himself  strictly  to  the 
study  of  the  vital  phenomena,  their  characters,  their  frequency, 
their  regularity  or  irregularity,  and  the  conditions  under  which 
they  originate. 

When  he  has  discovered  that  a  certain  phenomenon  always  takes 
place  in  the  presence  of  certain  conditions,  he  has  established  what 
is  called  a  general  principle,  or  a  Law  of  Physiology. 


INTEODUCTION.  53 

As,  for  example,  when  lie  has  ascertained  that  sensation  and 
motion  occupy  distinct  situations  in  every  part  of  the  nervous 
system. 

This  "  Law,"  however,  it  must  be  remembered,  is  not  a  discovery 
by  itself,  nor  does  it  give  him  any  new  information,  but  is  simply 
the  expression,  in  convenient  and  comprehensive  language,  of  the 
facts  with  which  he  was  already  previously  acquainted.  It  is  very 
dangerous,  therefore,  to  make  these  laws  or  general  principles  the 
subjects  of  our  study  instead  of  the  vital  phenomena,  or  to  suppose 
that  they  have  any  value,  except  as  the  expression  of  previously 
ascertained  facts.  Such  a  misconception  would  lead  to  bad  prac- 
tical results.  For  if  we  were  to  observe  a  phenomenon  in  discord- 
ance with  a  "  law"  or  "  principle,"  we  might  be  led  to  neglect  or 
misinterpret  the  phenomenon,  in  order  to  preserve  the  law.  But 
this  would  be  manifestly  incorrect.  For  the  law  is  not  superior  to 
the  phenomenon,  but,  on  the  contrary,  depends  upon  it,  and  derives 
its  whole  authority  from  it.  Such  mistakes,  however,  have  been 
repeatedly  made  in  Physiology,  and  have  frequently  retarded  its 
advance. 

lY.  There  is  only  one  means  by  which  Physiology  can  be 
studied :  that  is,  the  observation  of  nature.  Its  phenomena  cannot 
be  reasoned  out  by  themselves,  nor  inferred,  by  logical  sequence, 
form  any  original  principles,  nor  from  any  other  set  of  phenomena 
whatever. 

In  Mathematics  and  Philosophy,  on  the  other  hand,  certain  truths 
are  taken  for  granted,  or  perceived  by  intuition,  and  the  remainder 
afterward  derived  from  them  by  a  process  of  reasoning.  But  in 
Physiology,  as  in  all  the  other  natural  sciences,  there  is  no  such 
starting  point,  and  it  is  impossible  to  judge  of  the  character  of  a 
phenomenon  until  after  it  has  been  observed.  Thus,  the  only  way 
to  learn  what  action  is  exerted  by  nitric  acid  upon  carbonate  of 
soda  is  to  put  the  two  substances  together,  and  observe  the  changes 
which  take  place ;  for  there  is  nothing  in  the  general  characters  of 
these  two  substances  which  could  guide  us  in  anticipating  the  result. 

Neither  can  we  infer  the  truths  of  Physiology  from  those  of 
Anatomy,  nor  the  truths  of  one  part  of  Physiology  from  those  of 
another  part ;  but  all  must  be  ascertained  directly  and  separately 
by  observation. 

For,  although  one  department  of  natural  science  is  almost  always 
a  necessary  preliminary  to  the  study  of  another,  yet  the  facts  of 


54  INTRODUCTION. 

the  latter  can  never  he  in  the  least  degree  inferred  from  those  of  the 
former,  hut  must  he  studied  hy  themselves. 

Thus  Chemistry  is  essential  to  Anatomy,  because  certain  sub- 
stances, as  we  have  already  shown,  belonging  to  Chemistry,  such 
as  chloride  of  sodium,  occur  as  constituents  of  the  animal  body. 
Chemistry  teaches  us  the  composition,  reactions,  mode  of  crystal- 
lization, solubility,  &c.,  of  chloride  of  sodium ;  and  if  we  did  not 
know  these,  we  could  not  extract  it,  or  recognize  it  when  extracted 
from  the  body.  But,  however  well  we  might  know  the  chemistry 
of  this  substance,  we  could  never,  on  that  account,  infer  its  presence 
in  the  body  or  otherwise,  nor  in  what  quantities  nor  in  what  situa- 
tions it  would  present  itself  These  facts  must  be  ascertained  for 
themselves,  by  direct  investigation,  as  a  part  of  anatomy  proper. 

So,  again,  the  structure  of  the  body  in  a  state  of  rest,  or  its 
anatomy,  is  to  be  first  understood ;  but  its  active  phenomena  or  its 
physiology  must  then  be  ascertained  by  direct  observation  and 
experiment.  The  most  intimate  knowledge  of  the  minute  struc- 
ture of  the  muscular  and  nervous  fibres  could  not  teach  us  any- 
thing of  their  physiology.  It  is  only  by  experiment  that  we 
ascertain  one  of  them  to  be  contractile,  the  other  sensitive. 

Many  of  the  phenomena  of  life  are  chemical  in  their  character, 
and  it  is  requisite,  therefore,  that  the  physiologist  know  the  ordi- 
nary chemical  properties  of  the  substances  composing  the  animal 
frame.  But  no  amount  of  previous  chemical  knowledge  will 
enable  him  to  foretell  the  reactions  of  any  chemical  substance  in 
the  interior  of  the  body;  because  the  peculiar  conditions  under 
which  it  is  there  placed  modify  these  reactions,  as  an  elevation  or 
depression  of  temperature,  or  other  external  circumstance,  might 
modify  them  outside  the  body. 

We  must  not,  therefore,  attempt  to  deduce  the  chemical  phe- 
nomena of  physiology  from  any  previously  established  facts,  since 
these  are  no  safe  guide ;  but  must  study  them  by  themselves,  and 
depend  for  our  knowledge  of  them  upon  direct  observation  alone. 

Y.  By  the  term  Vital  phenomena,  we  mean  those  phenomena 
which  are  manifested  in  the  living  body,  and  which  are  character- 
istic of  its  functions. 

Some  of  these  phenomena  are  physical  or  mechanical  in  their 
character;  as,  for  example,  the  play  of  the  articulating  surfaces 
upon  each  other,  the  balancing  of  the  spinal  column  with  its  ap- 
pendages, the  action  of  the  elastic  ligaments.    Nevertheless,  these 


INTKODUCTION.  55 

phenomena,  thougli  strictly  physical  in  character,  are  often  entirely 
peculiar  and  different  from  those  seen  elsewhere,  because  the  me- 
chanism of  their  production  is  peculiar  in  its  details.  Thus  the 
human  voice  and  its  modulations  are  produced  in  the  larynx,  in 
accordance  with  the  general  physical  laws  of  sound;  but  the 
arrangement  of  the  elastic  and  movable  vocal  chords,  and  their 
relations  with  the  columns  of  air  above  and  below,  the  moist  and 
flexible  mucous  membrane,  and  the  contractile  muscles  outside,  are 
of  such  a  special  character  that  the  entire  apparatus,  as  well  as  the 
sounds  produced  by  it,  is  peculiar ;  and  its  action  cannot  be  properly 
compared  with  that  of  any  other  known  musical  instrument. 

In  the  same  manner,  the  movements  of  the  heart  are  so  compli- 
cated and  remarkable  that  they  cannot  be  comprehended,  even  by 
one  who  is  acquainted  with  the  anatomy  of  the  organ,  without  a 
direct  examination.  This  is  not  because  there  is  anything  essen- 
tially obscure  or  mysterious  in  their  nature,,  for  they  are  purely 
mechanical  in  character ;  but  because  their  conditions  are  so  pecu- 
liar, owing  to  the  tortuous  course  of  the  muscular  fibres,  their 
arrangement  in  interlacing  layers,  their  attachments  and  relations, 
that  their  combined  action  produces  an  effect  altogether  peculiar, 
and  one  which  is  not  similar  to  anything  outside  the  living  body. 

A  very  large  and  important  class  of  the  vital  phenomena  are 
those  of  a  chemical  character.  It  is  one  of  the  characteristics  of 
living  bodies  that  a  succession  of  chemical  actions,  combinations 
and  decompositions,  is  constantly  going  on  in  their  interior.  It  is 
one  of  the  necessary  conditions  of  the  existence  of  every  animal 
and  every  vegetable,  that  it  should  constantly  absorb  various  sub- 
stances from  without,  which  undergo  different  chemical  alterations 
in  its  interior,  and  are  finally  discharged  from  it  under  othey  forms. 
If  these  changes  be  prevented  from  taking  place,  life  is  immediately 
extinguished.  Thus  animals  constantly  absorb,  on  the  one  hand, 
water,  oxygen,  salts,  albumen,  oil,  sugar,  &c.,  and  give  up,  on  the 
other  hand,  to  the  surrounding  media,  carbonic  acid,  water,  ammonia, 
urea,  and  the  like ;  while  between  these  two  extreme  points,  of  ab- 
sorption and  exhalation,  there  take  place  a  multitude  of  different 
transformations  which  are  essential  to  the  continuance  of  life. 

Some  of  these  chemical  actions  are  the  same  with  those  which 
are  seen  outside  the  body ;  but  most  of  them-  are  entirely  peculiar, 
and  do  not  take  place,  and  cannot  be  made  to  take  place,  anywhere 
else.  This,  again,  is  not  because  there  is  anything  particularly 
mysterious  or  extraordinary  in  their  nature,  but  because  the  con- 


56  INTRODUCTIOlSr. 

ditions  necessary  for  their  accomplishment  exist  in  the  body,  and 
do  not  exist  elsewhere.  All  chemical  phenomena  are  liable  to  be 
modified  by  surrounding  conditions,  Maoy  reactions,  for  example, 
which  will  take  place  at  a  high  temperature,  will  not  take  place  at 
a  low  temperature,  and  vice  versa.  Some  will  take  place  in  the  light, 
but  not  in  the  dark ;  others  will  take  place  in  the  dark,  but  not  in 
the  light.  If  a  hot  concentrated  solution  of  sulphate  of  soda  be 
allowed  to  cool  in  contact  with  the  atmosphere,  it  crystallizes; 
covered  with  a  film  of  oil,  it  remains  fluid.  Because  a  chemical 
reaction,  therefore,  takes  place  under  one  set  of  conditions,  we  can- 
not be  at  all  sure  that  it  will  also  take  place  under  others,  which 
are  different. 

The  chemical  conditions  of  the  living  body  are  exceedingly  com- 
plicated. In  the  animal  solids  and  fluids  there  are  many  substances 
mingled  together  in  varying  quantities,  which  modify  or  interfere 
with  each  other's  reactions.  New  substances  are  constantly  entering 
by  absorption,  and  old  ones  leaving  by  exhalation ;  while  the  circu- 
lating fluids  are  constantly  passing  from  one  part  of  the  body  to 
another,  and  coming  in  contact  with  different  organs  of  different 
texture  and  composition.  All  these  conditions  are  peculiar,  and  so 
modify  the  chemical  actions  taking  place  in  the  body,  that  they  are 
unlike  those  met  with  anywhere  else. 

If  starch  and  iodine  be  mingled  together  in  a  watery  solution, 
they  unite  with  each  other,  and  strike  a  deep  opaque  blue  color ; 
but  if  they  be  mingled  in  the  blood,  no  such  reaction  takes  place, 
because  it  is  prevented  by  the  presence  of  certain  organic  substances 
which  interfere  with  it. 

If  dead  animal  matter  be  exposed  to  warmth,  air,  and  moisture, 
it  putrefies ;  but  if  introduced  into  the  living  stomach,  even  after 
putrefaction  has  commenced,  this  process  is  arrested,  because  the 
fluids  of  the  stomach  cause  the  animal  substance  to  undergo  a 
peculiar  transformation  (digestion),  after  which  the  bloodvessels 
immediately  remove  it  by  absorption.  There  are  also  certain  sub- 
stances which  make  their  appearance  in  the  living  body,  both  of 
animals  and  vegetables,  and  which  cannot  be  formed  elsewhere ; 
such  as  fibrin,  albumen,  casein,  pneumic  acid,  the  biliary  salts,  mor- 
phine, &c.  These  substances  cannot  be  manufactured  artificially, 
simply  because  the  necessary  conditions  cannot  be  imitated.  They 
require  for  their  production  the  presence  of  a  living  organism. 

The  chemical  phenomena  of  the  living  body  are,  therefore,  not 
different  in  their  nature  from  any  other  chemical  phenomena ;  but 


INTRODUCTION.  57 

they  are  different  in  their  conditions  and  in  their  results,  and  are 
consequently  peculiar  and  characteristic. 

Another  set  of  vital  phenomena  are  those  which  are  manifested 
in  the  processes  of  reproduction  and  development.  They  are  again 
entirely  distinct  from  any  phenomena  which  are  exhibited  by 
matter  not  endowed  with  life.  An  inorganic  substance,  even  when 
it  has  a  definite  form,  as,  for  example,  a  crystal  of  fluor  spar,  has 
no  particular  relation  to  any  similar  form  which  has  preceded,  or 
any  other  which  is  to  follow  it.  On  the  other  hand,  every  animal 
and  every  vegetable  owes  its  origin  to  preceding  animals  or  vege- 
tables of  the  same  kind ;  and  the  manner  in  which  this  production 
takes  place,  and  the  different  forms  through  which  the  new  body 
successively  passes  in  the  course  of  its  development,  coDstitute  the 
phenomena  of  reproduction.  These  phenomena  are  mostly  depend- 
ent on  the  chemical  processes  of  nutrition  and  growth,  which  take 
place  in  a  particular  direction  and  in  a  particular  manner ;  but  their 
results,  viz.,  the  production  of  a  connected  series  of  different  forms, 
constitute  a  separate  class  of  phenomena,  which  cannot  be  explained 
in  any  manner  by  the  preceding,  and  require,  therefore,  to  be  studied 
by  themselves. 

Another  set  of  vital  phenomena  are  those  which  belong  to  the 
nervous  system.  These,  like  the  processes  of  reproduction  and 
development,  depend  on  the  chemical  changes  of  nutrition  and 
growth.  That  is  to  say,  if  the  nutritive  processes  did  not  go  on  in 
a  healthy  manner,  and  maintain  the  nervous  system  in  a  healthy 
condition,  the  peculiar  phenomena  which  are  characteristic  of  it 
could  not  take  place.  The  nutritive  processes  are  necessary  condi- 
tions of  the  nervous  phenomena.  But  there  is  no  other  connection 
between  them ;  and  the  nervous  phenomena  themselves  are  distinct 
from  all  others,  both  in  their  nature  and  in  the  mode  in  which  they 
are  to  be  studied. 

A  troublesome  confusion  might  arise  if  we  were  to  neglect  the 
distinction  that  really  exists  between  these  different  sets  of  phe- 
nomena, and  confound  them  together  under  the  expectation  of 
thereby  simplifying  our  studies.  Since  this  can  only  be  done  by 
overlooking  real  points  of  difference,  its  effect  will  merely  be  to 
introduce  erroneous  ideas  and  suggest  unfounded  similarities,  and 
will  therefore  inevitably  retard  our  progress  instead  of  advancing  it. 

It  has  been  sometimes  maintained,  for  example,  that  all  the  vital 
phenomena,  those  of  the  nervous  system  included,  are  to  be  reduced 
to  the  chemical  changes  of  nutrition,  and  that  these  again  are  to  be 


58  .  INTRODUCTION. 

regarded  as  not  at  all  different  in  any  respect  from  tlie  ordinary 
cliemical  changes  taking  place  outside  tlie  body.  This,  however, 
is  not  only  erroneous  in  theory,  but  conduces  also  to  a  vicious 
mode  of  study.  For  it  draws  away  our  attention  from  the  phe- 
nomena themselves  and  their  real  characteristics,  and  leads  us  to 
deduce  one  set  of  phenomena  from  what  we  know  of  another ;  a 
method  which  we  have  already  shown  to  be  unsafe  and  pernicious. 
It  has  also  been  asserted  that  the  phenomena  of  the  nervous 
system  are  identical  with  those  of  electricity ;  for  no  other  reason 
than  that  there  exist  between  them  certain  general  resemblances. 
But  when  we  examine  the  phenomena  in  detail,  we  find  that,  beside 
these  general  resemblances,  there  are  many  essential  points  of  dis- 
similarity, which  must  be  suppressed  and  kept  out  of  sight  in  order 
to  sustain  the  idea  of  the  assumed  identity.  This  assumption  is 
consequently  a  forced  and  unnatural  one,  and  the  simplicity  which 
it  was  intended  to  introduce  into  our  physiological  theories  is 
imaginary  and  deceptive,  and  is  attained  only  by  sacrificing  a  part 
of  those  scientific  truths,  which  are  alone  the  real  object  of  our 
study.  We  should  avoid,  therefore,  making  any  such  unfounded 
comparisons ;  for  the  theoretical  simplicity  which  results  from  them 
does  not  compensate  for  the  loss  of  essential  scientific  details. 

yi.  The  study  of  Physiology  is  naturally  divided  into  three  dis- 
tinct Sections : — 

The  first  of  these  includes  everything  which  relates  to  the  Nutri- 
tion of  the  body  in  its  widest  sense.  It  comprises  the  history  of 
the  proximate  principles,  their  source,  the  manner  of  their  produc- 
tion, the  proportions  in  which  they  exist  in  different  kinds  of  food 
and  drink,  the  processes  of  digestion  and  absorption,  and  the  con- 
stitution of  the  circulating  fluids ;  then  the  physical  phenomena  of 
the  circulation  and  the  forces  by  which  it  is  accomplished;  the 
changes  which  the  blood  undergoes  in  different  parts  of  the  body ; 
all  the  phenomena,  both  physical  and  chemical,  of  respiration ;  those 
of  secretion  and  excretion,  and  the  character  and  destination  of  the 
secreted  and  excreted  fluids.  All  these  processes  have  reference  to 
a  common  object,  viz.,  the  preservation  of  the  internal  structure  and 
healthy  organization  of  the  individual.  "With  certain  modifications, 
they  take  place  in  vegetables  as  well  as  in  animals,  and  are  conse- 
quently known  by  the  name  of  the  vegetative  functions. 

The  Second  Section,  in  the  natural  order  of  study,  is  devoted  to 
the  phenomena  of  the  Nervous  System.    These  phenomena  are 


INTRODUCTION.  59 

not  exhibited  by  vegetables,  but  belong  exclusively  to  animal  or- 
ganizations. They  bring  the  animal  body  into  relation  with  the 
external  world,  and  preserve  it  from  external  dangers,  by  means  of 
sensation,  movement,  consciousness,  and  volition.  They  are  more 
particularly  distinguished  by  the  name  of  the  animal  functions. 

Lastly  comes  the  study  of  the  entire  process  of  Eeproduction. 
Its  phenomena,  again,  with  certain  modifications,  are  met  with  in 
both  animals  and  vegetables ;  and  might,  therefore,  with  some  pro- 
priety, be  included  under  the  head  of  vegetative  functions.  But 
their  distinguishing  peculiarity  is,  that  they  have  for  their  object 
the  production  of  new  organisms,  which  take  the  place  of  the  old 
and  remain  after  they  have  disappeared.  These  phenomena  do 
not,  therefore,  relate  to  the  preservation  of  the  individual,  but  to 
that  of  the  species;  and  any  study  which  concerns  the  species 
comes  properly  after  we  have  finished  everything  relating  to  the 
individual. 


SECTIOI(  I. 
NUTRITION. 


CHAPTER    I. 

PROXIMATE    PRINCIPLES    IN    GENERAL. 

The  study  of  ISTutrition  begins  naturally  with  that  of  the  proxi- 
mate principles,  or  the  substances  entering  into  the  composition  of 
the  different  parts  of  the  body,  and  the  different  kinds  of  food.  In 
examining  the  body,  the  anatomist  finds  that  it  is  composed,  first, 
of  various  parts,  which  are  easily  recognized  by  the  eye,  and  which 
occupy  distinct  situations.  In  the  case  of  the  human  body,  for 
example,  a  division  is  easily  made  of  the  entire  frame  into  the 
head,  neck,  trunk,  and  extremities.  Each  of  these  regions,  again, 
is  found,  on  examination,  to  contain  several  distinct  parts,  or 
"  organs,"  which  require  to  be  separated  from  each  other  by  dissec- 
tion, and  which  are  distinguished  by  their  form,  color,  texture,  and 
consistency.  In  a  single  limb,  for  example,  every  bone  and  every 
muscle  constitutes  a  distinct  organ.  In  the  trunk,  we  have  the 
heart,  the  lungs,  the  liver,  spleen,  kidneys,  spinal  cord,  &c.,  each  of 
which  is  also  a  distinct  organ.  When  a  number  of  organs,  differing 
in  size  and  form,  but  similar  in  texture,  are  found  scattered  through- 
out the  entire  frame,  or  a  large  portion  of  it,  they  form  a  connected 
set  or  order  of  parts,  which  is  called  a  "system."  Thus,  all  the 
muscles  taken  together  constitute  the  muscular  system ;  all  the 
bones,  the  osseous  system;  all  the  arteries,  the  arterial  system. 
Several  entirely  different  organs  may  also  be  connected  with  each 
other,  so  that  their  associated  actions  tend  to  accomplish  a  single 
object,  and  they  then  form  an  "apparatus."  Thus  the  heart,  arte- 
ries, capillaries,  and  veins,  together,  form  the  circulatory  apparatus; 
the  stomach,  liver,  pancreas,  intestine,  &c.,  the  digestive  apparatus. 
Every  organ,  again,  on  microscopic  examination,  is  seen  to  be  made 

(61  ) 


62  PROXIMATE    PRINCIPLES   IX    GENERAL. 

up  of  minute  bodies,  of  definite  size  and  figure,  wliicli  are  so  small 
as  to  be  invisible  to  tlie  naked  eye,  and  whicli,  after  separation 
from  each  other,  cannot  be  further  subdivided  without  destroying 
their  organization.  They  are,  therefore,  called  "anatomical  ele- 
ments." Thus,  in  the  liver,  they  are  hepatic  cells,  capillary  blood- 
vessels, the  fibres  of  Glisson's  capsule,  and  the  ultimate  filaments 
of  the  hepatic  nerves.  Lastly,  two  or  more  kinds  of  anatomical 
elements,  interwoven  with  each  other  in  a  particular  manner,  form 
a  "tissue."  Adipose  vesicles,  with  capillaries  and  nerve  tubes, 
form  adipose  tissue.  White  fibres  and  elastic  fibres,  with  capillaries 
and  nerve  tubes,  form  areolar  tissue.  Thus  the  solid  parts  of  the 
entire  body  are  made  up  of  anatomical  elements,  tissues,  organs, 
systems,  and  apparatuses.  Every  organized  frame,  and  even  every 
apparatus,  every  organ,  and  every  tissue,  is  made  up  of  different 
parts,  variously  interwoven  and  connected  with  each  other,  and  it 
is  this  character  which  constitutes  its  organization. 

But  beside  the  above  solid  forms,  there  are  also  certain  fluids, 
which  are  constantly  present  in  various  parts  of  the  body,  and  which, 
from  their  peculiar  constitution,  are  termed  "  animal  fluids."  These 
fluids  are  just  as  much  an  essential  part  of  the  body  as  the  solids. 
The  blood  and  the  lymph,  for  example,  the  pericardial  and  synovial 
fluids,  the  saliva,  which  always  exists  more  or  less  abundantly  in 
the  ducts  of  the  parotid  gland,  the  bile  in  the  biliary  ducts  and  the 
gall-bladder :  all  these  go  to  make  up  the  entire  body,  and  are  quite 
as  necessary  to  its  structure  as  the  muscles  or  the  nerves.  Now,  if 
these  fluids  be  examined,  they  are  found  to  be  made  up  of  many 
different  substances,  which  are  mingled  together  in  certain  propor- 
tions; these  proportions  being  constantly  maintained  at  or  about 
the  same  standard  by  the  natural  processes  of  nutrition.  Such  a 
fluid  is  termed  an  organized  fluid.  It  is  organized  by  virtue  of  the 
numerous  ingredients  which  enter  into  its  composition,  and  the 
regular  proportions  in  which  these  ingredients  are  maintained. 
Thus  in  the  plasma  of  the  blood,  we  have  albumen,  fibrin,  water, 
chlorides,  carbonates,  phosphates,  &c.  In  the  urine,  we  find  water, 
urea,  urate  of  soda,  creatine,  creatinine,  coloring  matter,  salts,  &c. 
These  substances,  which  are  mingled  together  so  as  to  make  up,  in 
each  instance,  by  their  intimate  union,  a  homogeneous  liquid,  are 
called  the  proximate  principles  of  the  animal  fluid. 

In  the  solids,  furthermore,  even  in  those  parts  which  are  appa- 
rently homogeneous,  there  is  the  same  mixture  of  different  ingre- 
dients.    In  the  hard  substance  of  bone,  for  example,  there  is,  first 


PROXIMATE    PRINCIPLES    IN    GENERAL.  63 

water,  which,  may  be  expelled  by  evaporation ;  second,  phosphate 
and  carbonate  of  lime,  which  may  be  extracted  by  the  proper  sol- 
vents ;  third,  ai  peculiar  animal  matter,  with  which  these  calcareous 
salts  are  in  union ;  and  fourth,  various  other  saline  substances,  in 
special  proportions.  In  the  muscular  tissue,  there  is  chloride  of 
potassium,  lactic  acid,  water,  salts,  albumen,  and  an  animal  matter 
termed  musculine.  The  diflerence  in  consistency  between  the  solids 
and  fluids  does  not,  therefore,  indicate  any  radical  difference  in  their 
constitution.  Both  are  equally  made  up  of  proximate  principles, 
mingled  together  in  various  proportions. 

It  is  important  to  understand,  however,  exactly  what  are  proxi- 
mate principles,  and  what  are  not  such  ;  for  since  these  principles 
are  extracted  from  the  animal  solids  and  fluids,  and  separated  from 
each  other  by  the  help  of  certain  chemical  manipulations,  such  as 
evaporation,  solution,  crystallization,  and  the  like,  it  might  be  sup- 
posed that  every  substance  which  could  be  extracted  from  an  organ- 
ized solid  or  fluid,  by  chemical  means,  should  be  considered  as  a 
proximate  principle.  That,  however,  is  not  the  case.  A  proximate 
principle  is  properly  defined  to  be  any  substance,  whether  simple  or 
compound,  chemically  speaking,  which  exists,  under  its  own  form,,  in  the 
animal  solid  or  fluid,  and  which  can  be  extracted  by  means  which  do 
not  alter  or  destroy  its  chemical  properties.  Phosphate  of  lime,  for 
example,  is  a  proximate  principle  of  bone,  but  phosphoric  acid  is 
not  so,  since  it  does  not  exist  as  such  in  the  bony  tissue,  but  is 
produced  only  by  the  decomposition  of  the  calcareous  salt ;  still 
less  phosphorus,  which  is  obtained  only  bv  the  decomposition  of 
the  phosphoric  acid. 

Proximate  principles  may,  in  fact,  be  said  to  exist  in  all  solids  or 
fluids  of  mixed  composition,  and  mp,y  be  extracted  from  them  by 
the  same  means  as  in  the  case  of  the  animal  tissues  or  secretions. 
Thus,  in  a  watery  solution  of  sugar,  we  have  two  proximate  prin- 
ciples, viz :  first,  the  water,  and  second,  the  sugar.  The  water  may 
be  separated  by  evaporation  and  condensation,  after  which  the 
sugar  remains  behind,  in  a  crystalline  form.  These  two  substances 
have,  therefore,  been  simply  separated  from  each  other  by  the  pro- 
cess of  evaporation.  They  have  not  been  decomposed,  nor  their 
chemical  properties  altered.  On  the  other  hand,  the  oxygen  and 
hydrogen  of  the  water  were  not  proximate  principles  of  the  original 
solution,  and  did  not  exist  in  it  under  their  own  forms,  but  only  in 
a  state  of  combination ;  forming,  in  this  condition,  a  fluid  substance 
(water),  endowed  with  sensible  properties  entirely  different  from 


64  PROXIMATE    PRINCIPLES    IN    GENERAL. 

theirs.  If  we  "wisti  to  ascertain,  accordingly,  the  nature  and  proper- 
ties of  a  saccharine  solution,  it  will  afford  us  but  little  satisfaction  to 
extract  its  ultimate  chemical  elements ;  for  its  nature  and  properties 
depend  not  so  much  on  the  presence  in  it  of  the  ultimate  elements, 
oxygen,  hydrogen,  and  carbon,  as  on  the  particular  forms  of  com- 
bination, viz.,  water  and  sugar,  under  which  they  are  present. 

It  is  very  essential,  therefore,  that  in  extracting  the  proximate 
principles  from  the  animal  body,  only  such  means  should  be  adopted 
as  will  isolate  the  substances  already  existing  in  the  tissues  and 
fluids,  without  decomposing  them,  or  altering  their  nature.  A 
neglect  of  this  rule  has  been  productive  of  much  injury  in  the  pur- 
suit of  organic  chemistry ;  for  chemists,  in  subjecting  the  animal 
tissues  to  the  action  of  acids  and  alkalies,  of  prolonged  boiling,  or 
of  too  intense  heat,  have  often  obtained,  at  the  end  of  the  analysis, 
many  substances  which  were  erroneously  described  as  proximate 
principles,  while  they  were  only  the  remains  of  an  altered  and  dis- 
organized material.  Thus,  the  fibrous  tissues,  if  boiled  steadily  for 
thirty-six  hours,  dissolve,  for  the  most  part,  at  the  end  of  that  time, 
in  the  boiling  water ;  and  on  cooling  the  whole  solution  solidifies 
into  a  homogeneous,  jelly-like  substance,  which  has  received  the 
name  of  gelatine.  But  this  gelatine  does  not  really  exist  in  the  body 
as  a  proximate  principle,  since  the  fibrous  tissue  which  produces  it 
is  not  at  first  soluble,  even  in  boiling  water,  and  its  ingredients 
become  altered  and  converted  into  a  gelatinous  matter  only  by  pro- 
longed ebullition.  So,  again,  an  animal  substance  containing  ace- 
tates or  lactates  of  soda  or  lime  will,  upon  incineration  in  the  open 
air,  yield  carbonates  of  the  same  bases,  the  organic  acid  having  been 
destroyed,  and  replaced  by  carbonic  acid ;  or  sulphur  and  phospho- 
rus, in  the  animal  tissue,  may  be  converted  by  the  same  means  into 
sulphuric  and  phosphoric  acids,  which,  decomposing  the  alkaline 
carbonates,  become  sulphates  and  phosphates.  In  either  case,  the 
analysis  of  the  tissues,  so  conducted,  will  be  a  deceptive  one,  and 
useless  for  all  anatomical  and  physiological  purposes,  because  its 
real  ingredients  have  been  decomposed,  and  replaced  by  others,  in 
the  process  of  manipulation. 

It  is  in  this  way  that  different  chemists,  operating  upon  the  same 
animal  solid  or  fluid,  by  following  different  plans  of  analysis,  have 
obtained  different  results ;  enumerating  as  ingredients  of  the  body 
many  artificially  formed  substances,  which  are  not,  in  reality, 
proximate  principles,  thereby  introducing  much  confusion  into 
physiological  chemistry. 


PROXIMATE    PRINCIPLES    IN    GENERAL.  65 

It  is  to  be  kept  constantly  in  view,  in  the  examination  of  an 
animal  tissue  or  fluid,  that  the  object  of  the  operation  is  simply  tlie 
separation  of  its  ingredients  from  each  other,  and  not  their  decomposi- 
tion or  ultimate  analysis.  Only  the  simplest  forms  of  chemical 
manipulation  should,  therefore,  be  employed.  The  substance  to 
be  exa,mined  should  first  be  subjected  to  evaporation,  in  order  to 
extract  and  estimate  its  water.  This  evaporation  must  be  conducted 
at  a  heat  not  above  212°  F.,  since  a  higher  temperature  would  de- 
stroy or  alter  some  of  the  animal  ingredients.  Then,  from  the 
dried  residue,  chloride  of  sodium,  alkaline  sulphates,  carbonates, 
and  phosphates  may  be  extracted  with  water.  Coloring  matters 
may  be  separated  by  alcohol.  Oils  may  be  dissolved  out  by  ether, 
&c.  &c.  When  a  chemical  decomposition  is  unavoidable,  it  must 
be  kept  in  sight  and  afterward  corrected.  Thus  the  glyko-cholate 
of  soda  of  the  bile  is  separated  from  certain  other  ingredients  by 
precipitating  it  with  acetate  of  lead,  forming  glyko-cholate  of  lead ; 
but  this  is  afterward  decomposed,  in  its  turn,  by  carbonate  of  soda, 
reproducing  the  original  glyko-cholate  of  soda.  Sometimes  it  is 
impossible  to  extract  a  proximate  principle  in  an  entirely  unaltered 
form.  Thus  the  fibrin  of  the  blood  can  be  separated  only  by  allow- 
ing it  to  coagulate ;  and  once  coagulated,  it  is  permanently  altered, 
and  can  no  longer  present  all  its  original  characters  of  fluidity,  &c., 
as  it  existed  beforehand  in  the  blood.  In  such  instances  as  this, 
we  can  only  make  allowance  for  an  unavoidable  difficulty,  and  be 
careful  that  the  substance  suffers  no  further  alteration.  By  bearing 
in  mind  the  above  considerations,  we  may  form  a  tolerably  correct 
estimate  of  the  nature  and  quantity  of  all  of  the  proximate  princi- 
ples existing  in  the  substance  under  examination. 

The  manner  in  which  the  proximate  principles  are  associated 
together,  so  as  to  form  the  animal  tissues,  is  deserving  of  notice. 
In  every  animal  solid  and  fluid,  there  is  a  considerable  number  of 
proximate  principles,  which  are  present  in  certain  proportions,  and 
which  are  so  united  with  each  other  that  the  mixture  presents  a 
homogeneous  appearance.  But  this  union  is  of  a  complicated  cha-  , 
racter ;  and  the  presence  of  each  ingredient  depends,  to  a  certain 
extent,  upon  that  of  the  others.  Some  of  them,  such  as  the  alkaline 
carbonates  and  phosphates,  are  in  solution  directly  in  the  water. 
Some,  which  are  insoluble  in  water,  are  held  in  solution  by  the 
presence  of  other  soluble  substances.  Thus,  phosphate  of  lime  is 
held  in  solution  in  the  urine  by  the  bi-phosphate  of  soda.  In  the 
blood,  it  is  dissolved  by  the  albumen,  which  is  itself  fluid  by  union 
5 


66  PROXIMATE    PRINCIPLES    IN    GENERAL. 

■with  the  water.  The  same  substance  may  he  fluid  in  one  part  of 
the  body,  and  solid  in  another  part.  Thus  in  the  blood  and  secre- 
tions the  water  is  fluid,  and  holds  in  solution  other  substances,  both 
animal  and  mineral,  while  in  the  bones  and  cartilages  it  is  solid — 
not  crystallized,  as  in  the  case  of  ice  or  of  saline  substances  which 
contain  water  of  crystallization,  but  amorphous  and  solid,  by  the 
fact  of  its  intimate  union  with  the  animal  and  saline  ingredients, 
which  are  abundant  in  quantity,  and  which  are  themselves  present 
in  the  solid  form.  Again,  the  phosphate  of  lime  in  the  blood  is 
fluid  by  solution  in  the  albumen  ;  but  in  the  bones  it  forms  a  solid 
substance  with  the  animal  matter  of  the  osseous  tissue;  and  yet 
the  union  of  the  two  is  as  intimate  and  homogeneous  in  the  bones 
as  in  the  blood.  A  proximate  principle,  therefore,  never  exists 
alone  in  any  part  of  the  body,  but  is  always  intimately  associated 
with  a  number  of  others,  by  a  kind  of  homogeneous  mixture  or 
solution. 

Every  animal  tissue  and  fluid  contains  a  number  of  proximate 
principles  which  are  present,  as  we  have  already  mentioned,  in 
certain  characteristic  proportions.  Thus,  water  is  present  in  very 
large  quantity  in  the  perspiration  and* the  saliva,  but  in  very  small 
quantity  in  the  bones  and  teeth.  Chloride  of  sodium  is  compara- 
tively abundant  in  the  blood  and  deficient  in  the  muscles.  On  the 
other  hand,  chloride  of  potassium  is  more  abundant  in  the  muscles, 
less  so  in  the  blood.  But  these  proportions,  it  is  important  to  ob- 
serve, are  nowhere  absolute  or  invariable.  There  is  a  great  differ- 
ence, in  this  respect,  between  the  chemical  composition  of  an  inor- 
ganic substance  and  the  anatomical  constitution  of  an  animal  fluid. 
The  former  is  always  constant  and  definite ;  the  latter  is  always 
subject  to  certain  variations.  Thus,  water  is  always  composed  of 
exactly  the  same  relative  quantities  of  oxygen  and  hydrogen ;  and 
if  these  proportions  be  altered  in  the  least,  it  thereby  ceases  to  be 
water,  and  is  converted  into  some  other  substance.  But  in  the 
urine,  the  proportions  of  water,  urea,  urate  of  soda,  phosphates, 
&c.,  vary  within  certain  limits  in  different  individuals,  and  even  in 
the  same  individual,  from  one  hour  to  another.  This  variation, 
which  is  almost  constantly  taking  place,  within  the  limits  of  health, 
is  characteristic  of  all  the  animal  solids  and  fluids ;  for  they  are 
composed  of  different  ingredients  which  are  supplied  by  absorption 
or  formed  in  the  interior,  and  which  are  constantly  given  up  again, 
under  the  same  or  different  forms,  to  the  surrounding  media  by  the 
unceasing  activity  of  the  vital  processes.     Every  variation,  then, 


PROXIMATE    PRINCIPLES    IN    GENERAL.  67 

in  the  general  condition  of  the  body,  as  a  whole,  is  accompanied  by 
a  corresponding  variation,  more  or  less  pronounced,  in  the  consti- 
tution of  its  different  parts.  This  constitution  is  consequently  of 
a  very  different  character  from  the  chemical  constitution  of  an 
oxide  or  a  salt.  "Whenever,  therefore,  we  meet  with  the  quanti- 
tative analysis  of  an  animal  fluid,  in  which  the  relative  quantity 
of  its  different  ingredients  is  represented  in  numbers,  we  must  ' 
understand  that  such  an  analysis  is  always  approximative,  and  not 
absolute. 

The  proximate  principles  are  naturally  divided  into  three  differ- 
ent classes. 

The  first  of  these  classes  comprises  all  the  proximate  principles 
which  are  purely  inorganic  in  their  nature.  These  principles  are 
derived  mostly  from  the  exterior.  They  are  found  everywhere,  in 
unorganized  as  well  as  in  organized  bodies ;  and  they  present  them- 
selves under  the  same  forms  and  with  the  same  properties  in  the 
interior  of  the  animal  frame  as  elsewhere.  They  are  crystallizable, 
and  have  a  definite  chemical  composition.  They  comprise  such 
substances  as  water,  chloride  of  sodium,  carbonate  and  phosphate 
of  lime,  &c. 

The  second  class  of  proximate  principles  is  known  as  crystal- 
lizable SUBSTANCES  OF  ORGANIC  ORIGIN.  This  is  the  name  given 
to  them  by  Eobin  and  VerdeiV  whose  classification  of  the  proxi- 
mate principles  is  the  best  which  has  yet  been  offered.  They  are 
crystallizable,  as  their  name  indicates,  and  have  a  definite  chemical 
composition.  They  are  said  to  be  of  "  organic  origin,"  because  they 
first  make  their  appearance  in  the  interior  of  organized  bodies,  and 
are  not  found  in  external  nature  as  the  ingredients  of  inorganic 
substances.     Such  are  the  different  kinds  of  sugar,  oil,  and  starch. 

The  third  class  comprises  a  very  extensive  and  important  order 
of  proximate  principles,  which  go  by  the  name  of  the  Organic 
Substances  proper.  They  are  sometimes  known  as  "  albuminoid" 
substances  or  "  protein  compounds."  The  name  organic  substances 
is  given  to  them  in  consequence  of  the  striking  difference  which 
exists  between  them  and  all  the  other  ingredients  of  the  body.  The 
substances  of  the  second  class  differ  from  those  of  the  first  by  their 

'  Chiiuie  Anatomique  et  Pliysiologique.     Paris,  1853. 


68  PEOXIMATE    PRINCIPLES    IN    GENERAL. 

exclusively  organic  origin,  but  they  resemble  the  latter  in  their  crys- 
tallizability  and  their  definite  chemical  composition ;  in  consequence 
of  which  their  chemical  investigation  may  be  pursued  in  nearly 
the  same  manner,  and  their  chemical  changes  expressed  in  nearly 
the  same  terms.  But  the  proximate  principles  of  the  third  class 
are  in  every  respect  peculiar.  They  have  an  exclusively  organic 
origin ;  not  being  found  except  as  ingredients  of  living  or  recently 
dead  animals  or  vegetables.  They  have  not  a  definite  chemical 
composition,  and  are  consequently  not  crystallizable ;  and  the  forms 
which  they  present,  and  the  chemical  changes  which  they  undergo 
in  the  body,  are  such  as  cannot  be  expressed  by  ordinary  chemical 
phraseology.  This  class  includes  such  substances  as  albumen, 
fibrin,  casein,  &c. 


PEOXIMATE    FRINCIPLES    OF    THE    FIRST    CLASS.  69 


CHAPTER    II. 

PEOXIMATE    PEINCIPLES     OF    THE    FIKST    CLASS. 

The  proximate  principles  of  tbe  first  class,  or  those  of  an  inor- 
ganic nature,  are  very  numerous.  Their  most  prominent  characters 
have  already  been  stated.  They  are  all  crystallizable,  and  have  a 
definite  chemical  composition.  They  are  met  with  extensively  in 
the  inorganic  world,  and  form  a  large  part  of  the  crust  of  the  earth. 
They  occur  abundantly  in  the  different  kinds  of  food  and  drink; 
and  are  necessary  ingredients  of  the  food,  since  they  are  necessary 
ingredients  of  the  animal  frame.  Some  of  them  are  found  universally 
in  all  parts  of  the  body,  others  are  met  with  only  in  particular 
regions ;  but  there  are  hardly  any  which  are  not  present  at  the 
same  time  in  more  than  one  animal  solid  or  fluid.  The  following 
are  the  most  prominent  of  them,  arranged  in  the  order  of  their 
respective  importance. 

1.  Water. — Water  is  universally  present  in  all  the  tissues  and 
fluids  of  the  body.  It  is  abundant  in  the  blood  and  secretions, 
where  its  presence  is  indispensable  in  order  to  give  them  the  fluidity 
which  is  necessary  to  the  performance  of  their  functions;  for  it 
is  by  the  blood  and  secretions  that  new  substances  are  introduced 
into  the  body,  and  old  ingredients  discharged.  And  it  is  a  neces- 
sary condition  both  of  the  introduction  and  discharge  of  substances 
naturally  solid,  that  they  assume,  for  the  time  being,  a  fluid  form ; 
water  is  therefore  an  essential  ingredient  of  the  fluids,  for  it  holds 
their  solid  materials  in  solution,  and  enables  them  to  pass  and  repass 
through  the  animal  frame. 

But  water  is  an  ingredient  also  of  the  solids.  For  if  we  take  a 
muscle  or  a  cartilage,  and  expose  it  to  a  gentle  heat  in  dry  air,  it 
loses  water  by  evaporation,  diminishes  in  size  and  weight,  and  be- 
comes dense  and  stiff'.  Even  the  bones  and  teeth  lose  water  by 
evaporation  in  this  way,  though  in  smaller  quantity.  In  all  these 
solid  and  semi-solid  tissues,  the  water  which  they  contain  is  useful 


70 


PEOXIMATE    PRINCIPLES    OP    THE    FIRST    CLASS. 


by  giving  tliem  tlie  special  consistency  which  is  characteristic  of 
them,  and  which  would  be  lost  without  it.  Thus  a  tendon,  in  its 
natural  condition,  is  white,  glistening,  and  opaque ;  and  though  very 
strong,  perfectly  flexible.  If  its  water  be  expelled  by  evaporation 
it  becomes  yellowish  in  color,  shrivelled,  semi-transparent,  inflexi- 
ble, and  totally  unfit  for  performing  its  mechanical  functions.  The 
same  thing  is  true  of  the  skin,  muscles,  cartilages,  &c. 

The  following  is  a  list,  compiled  by  Eobin  and  Yerdeil  from 
various  observers,  showing  the  proportion  of  water  per  thousand 
parts,  in  different  solids  and  fluids : — 


Quantity  of  Water  in  1,000  parts  in 


Epidermis 
Teeth 
Bones 
Cartilage  . 
Muscles    . 
Ligaments 
Brain 
Blood 
Synovial  fluid 


37 
100 
130 

550 
750 
768 
789 
795 
805 


Bile  . 

Milk 

Pancreatic  juice 

Urine 

Lympli 

Gastric  juice 

Perspiration 

Saliva 


887 
900 
936 
960 
975 
986 
995 


According  to  the  best  calculations,  water  constitutes,  in  the 
human  subject,  between  two-thirds  and  three-quarters  of  the  entire 
weight  of  the  body. 

The  water  which  thus  forms  a  part  of  the  animal  frame  is  derived 
from  without.  It  is  taken  in  the  different  kinds  of  drink,  and  also 
forms  an  abundant  ingredient  in  the  various  articles  of  food.  For 
no  articles  of  food  are  taken  in  an  absolutely  dry  state,  but  all 
contain  a  larger  or  smaller  quantity  of  water,  which  may  readily 
be  expelled  by  evaporation.  The  quantity  of  water,  therefore, 
which  is  daily  taken  into  the  system,  cannot  be  ascertained  in  any 
case  by  simply  measuring  the  quantity  of  drink,  but  its  proportion 
in  the  solid  food,  taken  at  the  same  time,  must  also  be  determined 
by  experiment,  and  this  ascertained  quantity  added  to  that  which 
is  taken  in  with  the  fluids.  By  measuring  the  quantity  of  fluid 
taken  with  the  drink,  and  calculating  in  addition  the  proportion 
existing  in  the  solid  food,  we  have  found  that,  for  a  healthy  adult 
man,  the  ordinary  quantity  of  water  introduced  per  day,  is  a  little 
over  4 J  pounds. 

After  forming  part  of  the  animal  solids  and  fluids,  and  taking 
part  in  the  various  physical  and  chemical  processes  of  the  body,  the 
water  is  again  discharged ;  for  its  presence  in  the  body,  like  that 
of  all  the  other  proximate  principles,  is  not  permanent,  but  only 


CHLORIDE    OF    SODIUM.  71 

temporary.  After  being  taken  in  with  the  food  and  drink,  it  is 
associated  with  other  principles  in  the  fluids  and  solids,  passing 
from  the  intestine  to  the  blood,  and  from  the  blood  to  the  tissues 
and  secretions.  It  afterward  makes  its  exit  from  the  body,  from 
which  it  is  discharged  by  four  different  passages,  viz.,  in  a  liquid 
form  with  the  urine  and  the  feces,  and  in  a  gaseous  form  with  the 
breath  and  the  perspiration.  Of  all  the  water  which  is  expelled  in 
this  way,  about  48  per  cent,  is  discharged  with  the  urine  and  feces,^ 
and  about  62  per  cent,  by  the  lungs  and  skin.  The  researches  of 
Lavoisier  and  Seguin,  Valentin,  and  others,  show  that  from  a  pound 
and  a  half  to  two  pounds  is  discharged  daily  by  the  skin,  a  little 
over  one  pound  by  exhalation  from  the  lungs,  and  a  little  over  two 
pounds  by  the  urine.  Both  the  absolute  and  relative  amount  dis- 
charged, both  in  a  liquid  and  gaseous  form,  varies  according  to 
circumstances.  There  is  particularly  a  compensating  action  in  this 
respect  between  the  kidneys  and  the  skin,  so  that  when  the  cutane- 
ous perspiration  is  very  abundant  the  urine  is  less  so,  and  vice  versa. 
The  quantity  of  water  exhaled  from  the  lungs  varies  also  with  the 
state  of  the  pulmonary  circulation,  and  with  the  temperature  and 
dryness  of  the  atmosphere.  The  water  is  not  discharged  at  any 
time  in  a  state  of  purity,  but  is  mingled  in  the  urine  and  feces  with 
saline  substances  which  it  holds  in  solution,  and  in  the  cutaneous 
and  pulmonary  exhalations  with  animal  vapors  and  odoriferous 
substances  of  various  kinds.  In  the  perspiration  it  is  also  mingled 
with  saline  substances,  which  it  leaves  behind  on  evaporation. 

2.  Chloride  of  Sodium. — This  substance  is  foimd,  like  water^ 
throughout  the  different  tissues  and  fluids  of  the  body.  The  only 
exception  to  this  is  perhaps  the  enamel  of  the  teeth,  where  it  has 
not  yet  been  discovered.  Its  presence  is  important  in  the  body,  as 
regulating  the  phenomena  of  endosmosis  and  exosmosis  in  different 
parts  of  the  frame.  For  we  know  that  a  solution  of  common  salt 
passes  through  animal  membranes  much  less  readily  than  pure 
water ;  and  tissues  which  have  been  desiccated  will  absorb  pure 
water  more  abundantly  than  a  saline  solution.  It  must  not  be  sup- 
posed, however,  that  the  presence  or  absence  of  chloride  of  sodium, 
or  its  varying  quantity  in  the  animal  fluids,  is  the  only  condition 
which  regulates  their  transudation  through  the  animal  membranes. 
The  manner  in  which  endosmosis  and  exosmosis  take  place  in  the 

'  Op.  cit.,  vol.  ii.  pp.  143  and  145. 


2 

Bile 

3.5 

2.5 

Blood 

4.5 

1 

Mucus     . 

6 

1.5 

Aqueous  humor 

.       11 

3 

Vitreous  humor 

.       14 

72  PROXIMATE    PRINCIPLES    OF   THE    FIRST   CLASS. 

animal  frame  depends  upon  the  relative  quantity  of  all  the  ingre- 
dients of  the  fluids,  as  well  as  on  the  constitution  of  the  solids 
themselves;  and  the  chloride  of  sodium,  as  one  ingredient  among 
many,  influences  these  phenomena  to  a  great  extent,  though  it  does 
not  regulate  them  exclusively. 

It  exerts  also  an  important  influence  on  the  solution  of  various 
other  ingredients,  with  which  it  is  associated.  Thus,  in  the  blood 
it  increases  the  solubility  of  the  albumen,  and  perhaps  also  of  the 
earthy  phosphates.  The  blood-globules,  again,  which  become  dis- 
integrated and  dissolved  in  a  solution  of  pure  albumen,  are  main- 
tained in  a  state  of  integrity  by  the  presence  of  a  small  quantity  of 
chloride  of  sodium. 

It  exists  in  the  following  proportions  in  several  of  the  solids  and 
fluids :' — 

Quantity  of  Chlokide  of  Sodium  ins  1,000  parts  in  the 

Muscles   . 

Boues 

Milk 

Saliva 

Urine 

In  the  blood  it  is  rather  more  abundant  than  all  the  other  saline 
ingredients  taken  together. 

Since  chloride  of  sodium  is  so  universally  present  in  all  parts  of 
the  body,  it  is  an  important  ingredient  also  of  the  food.  It  occurs, 
of  course,  in  all  animal  food,  in  the  quantities  in  which  it  naturally 
exists  in  the  corresponding  tissues;  and  in  vegetable  food  also, 
though  in  smaller  amount.  Its  proportion  in  muscular  flesh, 
however,  is  much  less  than  in  the  blood  and  other  fluids.  Conse- 
quently, it  is  not  supplied  in  sufficient  quantity  as  an  ingredient  of 
animal  and  vegetable  food,  but  is  taken  also  by  itself  as  a  condi- 
ment. There  is  no  other  substance  so  universally  used  by  all  races 
and  conditions  of  men,  as  an  addition  to  the  food,  as  chloride  of 
sodium.  This  custom  does  not  simply  depend  on  a  fancy  for  grati- 
fying the  palate,  but  is  based  upon  an  instinctive  desire  for  a  sub- 
stance which  is  necessary  to  the  proper  constitution  of  the  tissues 
and  fluids.  Even  the  herbivorous  animals  are  greedy  of  it,  and  if 
freely  supplied  with  it,  are  kept  in  a  much  better  condition  than 
when  deprived  of  its  use. 

The  importance  of  chloride  of  sodium  in  this  respect  has  been 
well   demonstrated  by  Boussingault,  in   his  experiments  on  the 

"  Roblu  and  Yerdeil. 


CHLORIDE    OF    SODIUM.  Yd 

fattening  of  animals.  These  observations  were  made  upon  six 
bullocks,  selected,  as  nearly  as  possible,  of  the  same  age  and  vigor, 
and  subjected  to  comparative  experiment.  They  were  all  supplied 
with  an  abundance  of  nutritious  food ;  but  three  of  them  (lot  ISTo. 
1)  received  also  a  little  over  500  grains  of  salt  each  per  day.  The 
remaining  three  (lot  No.  2)  received  no  salt,  but  in  other  respects 
were  treated  like  the  first.  The  result  of  these  experiments  is  given 
by  Boussingault  as  follows : — ^ 

"  Though  salt  administered  with  the  food  has  but  little  effect  in 
increasing  the  size  of  the  animal,  it  appears  to  exert  a  favorable 
influence  upon  his  qualities  and  general  aspect.  Until  the  end  of 
March  (the  experiment  began  in  October)  the  two  lots  experimented 
on  did  not  present  any  marked  difference  in  their  appearance ;  but 
in  the  course  of  the  following  April,  this  difference  became  quite 
manifest,  even  to  an  unpractised  eye.  The  lot  No.  2  had  then  been 
without  salt  for  six  months.  In  the  animals  of  both  lots  the  skin 
had  a  fine  and  substantial  texture,  easily  stretched  and  separated 
from  the  ribs ;  but  the  hair,  which  was  tarnished  and  disordered  in 
the  bullocks  of  the  second  lot,  was  smooth  and  glistening  in  those 
of  the  first.  As  the  experiment  went  on,  these  characters  became 
more  marked ;  and  at  the  beginning  of  October  the  animals  of  lot 
No.  2,  after  going  without  salt  for  an  entire  year,  presented  a  rough 
and  tangled  hide,  with  patches  here  and  there  where  the  skin  was 
entirely  uncovered.  The  bullocks  of  lot  No.  1  retained,  on  the 
contrary,  the  ordinary  aspect  of  stall-fed  animals.  Their  vivacity 
and  their  frequent  attempts  at  mounting  contrasted  strongly  with 
the  dull  and  unexcitable  aspect  presented  by  the  others.  No  doubt, 
the  first  lot  would  have  commanded  a  higher  price  in  the  market 
than  the  second." 

Chloride  of  sodium  acts  also  in  a  favorable  manner  by  exciting 
the  digestive  fluids,  and  assisting  in  this  way  the  solution  of  the 
food.  For  food  which  is  tasteless,  however  nutritious  it  may  be  in 
other  respects,  is  taken  with  reluctance  and  digested  with  difficulty ; 
while  the  attractive  flavor  which  is  developed  by  cooking,  and  by 
the  addition  of  salt  and  other  condiments  in  proper  proportion, 
excites  the  secretion  of  the  saliva  and  gastric  juice,  and  facilitates 
consequently  the  whole  process  of  digestion.  The  chloride  of 
sodium  is  then  taken  up  by  absorption  from  the  intestine,  and  is 
deposited  in  various  quantities  in  different  parts  of  the  body. 

'  Chimie  Agricole,  Paris,  1854,  p.  271. 


74  PROXIMATE    PRINCIPLES    OF    THE    FIRST    CLASS. 

It  is  discharged  with  the  urine;  mucus,  cutaneous  perspiration, 
&c.,  in  solution  in  the  water  of  these  fluids.  According  to  the  esti- 
mates of  M.  Barral.'  a  small  quantity  of  chloride  of  sodium  dis- 
appears in  the  body ;  since  he  finds  by  accurate  comparison  that  all 
the  salt  introduced  with  the  food  is  not  to  be  found  in  the  excreted 
fluids,  but  that  about  one-fifth  of  it  remains  unaccounted  for.  This 
portion  is  supposed  to  undergo  a  double  decomposition  in  the  blood 
with  phosphate  of  potassa,  forming  chloride  of  potassium  and  phos- 
phate of  soda.  By  far  the  greater  part  of  the  chloride  of  sodium, 
however,  escapes  under  its  own  form  with  the  secretions. 

3.  Chloride  of  Potassium. — This  substance  is  found  in  the 
muscles,  the  blood,  the  milk,  the  urine,  and  various  other  fluids 
and  iissues  of  the  body.  It  is  not  so  universally  present  as  chlo- 
ride of  sodium,  and  not  so  important  as  a  proximate  principle. 
In  some  parts  of  the  body  it  is  more  abundant  than  the  latter  salt, 
in  others  less  so.  Thus,  in  the  blood  there  is  more  chloride  of 
sodium  than  chloride  of  potasssium,  but  in  the  muscles  there  is  more 
chloride  of  potassium  than  chloride  of  sodium.  This  substance  is 
always  in  a  fluid  form,  by  its  ready  solubility  in  water,  and  is  easily 
separated  by  lixiviation.  It  is  introduced  mostly  with  the  food,  but 
is  probably  formed  partly  in  the  interior  of  the  body  from  chloride 
of  sodium  by  double  decomposition,  as  already  mentioned.  It  is 
discharged  with  the  mucus,  the  saliva,  and  the  urine. 

4.  Phosphate  of  Lime. — This  is  perhaps  the  most  important 

of  the  mineral  ingredients  of  the  body  next  to  chloride  of  sodium. 

It  is  met  with  universally,  in  every  tissue  and  every  fluid.     Its 

quantity,  however,  varies  very  much  in  difierent  parts,  as  will  be 

seen  by  the  following  list : — 

Quantity  of  Phosphate  of  Lime  in  1,000  parts  in  the 
Enamel  of  tlie  teeth  .         .     885  Muscles     ....     2.5 

Dentine      .         .         .         .643  Blood        .         .         .         .0.3 

Bones         ....     550  Gastric  juice     .         .         .     0.4 

Cartilages  ...       40 

It  occurs  also  under  different  physical  conditions.  In  the  bones, 
teeth,  and  cartilages  it  is  solid,  and  gives  to  these  tissues  the  resist- 
ance and  solidity  which  are  characteristic  of  them.  The  calcareous 
salt  is  not,  however,  in  these  instances,  simply  deposited  mechani- 
cally in  the  substance  of  the  bone  or  cartilage  as  a  granular  powder, 

'  In  Robin  and  Verdeil,  op.  cit.,  vol.  ii.  193. 


PHOSPHATE    OF    LIME. 


75 


Fig.  1. 


but  is  intimately  united  witli  the  animal  matter  of  the  tissues,  like 
a  coloring  matter  in  colored  glass,  so  as  to  present  a  more  or  less 
homogeneous  appearance.  It  can,  however,  be  readily  dissolved 
out  by  maceration  in  dilute  muriatic  acid,  leaving  behind  the 
animal  substance,  which  still  retains  the  original  form  of  the  bone 
or  cartilage.  It  is  not,  therefore,  united  with  the  animal  matter  so 
as  to  lose  its  identity  and  form  a  new  chemical  substance,  as  where 
an  acid  combines  with  an  alkali  to  form  a  salt,  but  in  the  same 
manner  as  salt  unites  with  water  in  a  saline  solution,  both  sub- 
stances retaining  their  original  character  and  composition,  but  so 
intimately  associated  that  they  cannot  be  separated  by  mechanical 
means. 

In  the  blood,  phosphate  of  lime  is  in  a  liquid  form,  notwithstand- 
ing its  insolubility  in  water  and  in  alkaline  fluids,  being  held  in 
solution  by  the  albuminous  matters  of  the  circulating  fluid.  In  the 
urine,  it  is  retained  in  solution  by  the  bi-phosphate  of  soda. 

In  all  the  solid  tissues  it  is  useful  by  giving  to  them  their  proper 
consistence  and  solidity.  For  example,  in  the  ena- 
mel of  the  teeth,  the  hardest  tissue  of  the  body,  it 
predominates  very  much  over  the  animal  matter, 
and  is  present  in  greater  abundance  there  than  in 
any  other  part  of  the  frame.  In  the  dentine,  a 
softer  tissue,  it  is  in  somewhat  smaller  quantity, 
and  in  the  bones  smaller  still ;  though  in  the  bones 
it  continues  to  form  more  than  one-half  the  entire 
mass  of  the  osseous  substance.  The  importance  of 
phosphate  of  lime,  in  communicating  to  bones  their 
natural  stiffness  and  consistency,  may  be  readily 
shown  by  the  alteration  which  they  suffer  from  its 
removal.  If  a  long  bone  be  macerated  in  dilute 
muriatic  acid,  the  earthy  salt,  as  already  mentioned, 
is  entirely  dissolved  out,  after  which  the  bone  loses 
its  rigidity,  and  may  be  bent  or  twisted  in  any  di- 
rection without  breaking.  (Fig.  1.) 

Whenever  the  nutrition  of  the  bone  during  life 
is  interfered  with  from  any  pathological  cause,  so 
that  its  phosphate  of  lime  becomes  deficient  in 
amount,  a  softening  of  the  osseous  tissue  is  the 
consequence,  by  which  the  bones  yield  to  external 
pressure,  and  become  more  or  less  distorted.   (Osteo-malakia.) 

After  forming,  for  a  time,  a  part  of  the  tissues  and  fluids,  the 


Fibula  tied  ix 
A  k:iot,  after  ma- 
ceration in  a  dilute 
acid.  (From  a  speci- 
men in  tlie  museum 
of  tlie  Coll.  of  Pliysi- 
ciaus  aud  Surgeons.) 


76  PROXIMATE    PRINCIPLES    OF    THE    FIRST    CLASS. 

pTiosphate  of  lime  is  discharged  from  the  body  by  the  urine,  the 
perspiration,  mucus,  &c.  Much  the  larger  portion  is  discharged  by 
the  urine.  A  small  quantity  also  occurs  in  the  feces,  but  this  is  pro- 
bably only  the  superfluous  residue  of  what  is  taken  in  with  the  food. 

5.  Carbonate  of  Lime. — Carbonate  of  lime  is  to  be  found  in 
the  bones,  and  sometimes  in  the  urine.  The  concretions  of  the 
internal  ear  are  almost  entirely  formed  of  it.  It  very  probably 
occurs  also  in  the  blood,  teeth,  cartilages,  and  sebaceous  matter; 
but  its  presence  here  is  not  quite  certain,  since  it  may  have  been 
produced  from  the  lactate,  or  other  organic  combination,  by  the 
process  of  incineration.  In  the  bones,  it  is  in  much  smaller  quan- 
tity than  the  phosphate.  Its  solubility  in  the  blood  and  the  urine 
is  accounted  for  by  the  presence  of  free  carbonic  acid,  and  also  of 
chloride  of  potassium,  both  of  which  substances  exert  a  solvent 
action  on  carbonate  of  lime. 

6.  Carbonate  of  Soda. — This  substance  exists  in  the  bones, 
blood,  saliva,  lymph,  and  urine.  As  it  is  readily  soluble  in  water, 
it  naturally  assumes  the  liquid  form  in  the  animal  fluids.  It  is 
important  principally  as  giving  to  the  blood  its  alkalescent  reaction, 
by  which  the  solution  of  the  albumen  is  facilitated,  and  various 
other  chemico-physiological  processes  in  the  blood  accomplished. 
The  alkalescence  of  the  blood  is,  in  fact,  necessary  to  life ;  for  it  is 
found  that,  in  the  living  animal,  if  a  mineral  acid  be  gradually 
injected  into  the  blood,  so  dilute  as  not  to  coagulate  the  albumen, 
death  takes  place  before  its  alkaline  reaction  has  been  completely 
neutralized.' 

The  carbonate  of  soda  of  the  blood  is  partly  introduced  as  such 
with  the  food ;  but  the  greater  part  of  it  is  formed  within  the  body 
by  the  decomposition  of  other  salts,  introduced  with  certain  fruits 
and  vegetables.  These  fruits  and  vegetables,  such  as  apples,  cher- 
ries, grapes,  potatoes,  &c.,  contain  malates,  tartrates,  and  citrates 
of  soda  and  potassa.  Now,  it  has  been  often  noticed  that,  after 
the  use  of  acescent  fruits  and  vegetables  containing  the  above  salts, 
the  urine  becomes  alkaline  in  reaction  from  the  presence  of  the 
alkaline  carbonates.  Lehmann'  found,  by  experiments  upon  his 
own  person,  that,  within  thirteen  minutes  after  taking  half  an  ounce 

'  01.  Bernard.  Lectures  on  the  Blood ;  reported  by  W.  F.  Atlee,  M.  D.  Phila- 
delphia, 1854,  p.  31. 

'^  Physiological  Chemistry.     Philadelphia  ed.,  vol.  i.  p.  97. 


PHOSPHATES    OF    MAGNESIA,    SODA,   AND    POTASSA.       77 

of  lactate  of  soda,  the  urine  had.  an  alkaline  reaction.  He  also  ob- 
served that,  if  a  solution  of  lactate  of  soda  were  injected  into  the 
jugular  vein  of  a  dog,  the  urine  became  alkaline  at  the  end  of  five, 
or,  at  the  latest,  of  twelve  minutes.  The  conversion  of  these  salts 
into  carbonates  takes  place,  therefore,  not  in  the  intestine  but  in  the 
blood.  The  same  observer'  found  that,  in  many  persons  living  on 
a  mixed  diet,  the  urine  became  alkaline  in  two  or  three  hours  after 
swallowing  ten  grains  of  acetate  of  soda.-  These  salts,  therefore, 
on  being  introduced  into  the  animal  body,  are  decomposed.  Their 
organic  acid  is  destroyed  and  replaced  by  carbonic  acid ;  and  they 
are  then  discharged  under  the  form  of  carbonates  of  soda  and  potassa. 

7.  Caebonate  of  Potassa. — This  substance  occurs  in  very 
nearly  the  same  situations  as  the  last.  In  the  blood,  however,  it  is 
in  smaller  quantity.  It  is  mostly  produced,  as  above  stated,  by 
the  decomposition  of  the  malate,  tartrate,  and  citrate,  in  the  same 
manner  as  the  carbonate  of  soda.  Its  function  is  also  the  same  as 
that  of  the  soda  salt,  and  it  is  discharged  in  the  same  manner  from 
the  body. 

8.  Phosphates  of  Magnesia,  Soda,  and  Potassa. — All  these 
substances  exist  universally  in  all  the  solids  and  fluids  of  the  body, 
but  in  very  small  quantity.  The  phosphates  of  soda  and  potassa 
are  easily  dissolved  in  the  animal  fluids,  owing  to  their  ready  solu- 
bility in  water.  The  phosphate  of  magnesia  is  held  in  solution  in 
the  blood  by  the  alkaline  chlorides  and  phosphates ;  in  the  urine, 
by  the  acid  phosphate  of  soda. 

A  peculiar  relation  exists  between  the  alkaline  phosphates  and 
carbonates  in  different  classes  of  animals.  For  while  the  fluids  of 
carnivorous  animals  contain  a  preponderance  of  the  phosphates, 
those  of  the  herbivora  contain  a  preponderance  of  the  carbonates : 
a  peculiarity  readily  understood  when  we  recollect  that  muscular 
flesh  and  the  animal  tissues  generally  are  comparatively  abundant 
in  phosphates ;  while  vegetable  substances  abound  in  salts  of  the 
organic  acids,  which  give  rise,  as  already  described,  by  their  decom- 
position in  the  blood,  to  the  alkaline  carbonates. 

The  proximate  principles  included  in  the  above  list  resemble 
each  other  not  only  in  their  inorganic  origin,  their  crystallizability, 

'  Physiological  Chemistry,  vol.  ii.  p.  130. 


78  PEOXIMATE    PRINCIPLES    OF    THE    FIRST    CLASS. 

and  their  definite  chemical  composition,  but  also  in  the  part  which 
they  take  in  the  constitution  of  the  animal  frame,  Thej  are 
distinguished  in  this  respect,  first  by  being  derived  entirely  from 
without.  There  are  a  few  exceptions  to  this  rule ;  as,  for  example, 
in  the  case  of  the  alkaline  carbonates,  which  partly  originate  in 
the  body  from  the  decomposition  of  malates,  tartrates,  &c.  These, 
however,  are  only  exceptions ;  and  in  general,  the  proximate  prin- 
ciples belonging  to  the  first  class  are  introduced  with  the  food, 
and  taken  up  by  the  animal  tissues  in  precisely  the  same  form 
under  which  they  occur  in  external  nature.  The  carbonate  of  lime 
in  the  bones,  the  chloride  of  sodium  in  the  blood  and  tissues,  are 
the  same  substances  whicb  are  met  with  in  the  calcareous  rocks, 
and  in  solution  in  sea  water.  They  do  not  suffer  any  chemical 
alteration  in  becoming  constituent  parts  of  the  animal  frame. 

They  are  equally  exempt,  as  a  general  rule,  from  any  alteration 
while  they  remain  in  the  body,  and  during  their  passage  through 
it.  The  exceptions  to  this  rule  are  very  few ;  as,  for  example,  where 
a  small  part  of  the  chloride  of  sodium  suffers  double  decomposition 
with  phosphate  of  potassa,  giving  rise  to  chloride  of  potassium  and 
phosphate  of  soda ;  or  where  the  phosphate  of  soda  itself  gives  up 
a  part  of  its  base  to  an  organic  acid  (uric),  and  is  converted  in  this 
way  into  a  bi-phosphate  of  soda. 

Kearly  the  whole  of  these  substances,  finally,  are  taken  up  un- 
changed from  the  tissues,  and  discharged  unchanged  with  the  excre- 
tions. Thus  we  find  the  phosphate  of  lime  and  the  chloride  of  so- 
dium, which  were  taken  in  with  the  food,  discharged  again  under 
the  same  form  in  the  urine.  They  do  not,  therefore,  for  the  most 
part,  participate  directly  in  the  chemical  changes  going  on  in  the 
body ;  but  only  serve  by  their  presence  to  enable  those  changes  to 
be  accomplished  in  the  other  ingredients  of  the  animal  frame,  which 
are  necessary  to  the  process  of  nutrition. 


PBOXIMATE    PKINCIPLES    OF    THE    SECOND    CLASS.         79 


CHAPTER    III. 

PEOXIMATE   PRINCIPLES   OF  THE  SECOND   CLASS. 

The  proximate  principles  belonging  to  tlie  second  class  are 
divided  into  three  principal  groups,  viz :  starch,  sugar,  and  oil. 
They  are  distinguished,  in  the  first  place,  bj  their  organic  origin. 
Unlike  the  principles  of  the  first  class,  they  do  not  exist  in 
external  nature,  but  are  only  found  as  ingredients  of  organized 
bodies.  They  exist  both  in  animals  and  in  vegetables,  though  in 
somewhat  different  proportions.  All  the  substances  belonging  to 
this  class  have  a  definite  chemical  composition ;  and  are  further 
distinguished  by  the  fact  that  they  are  composed  of  oxygen, 
hydrogen,  and  carbon  alone,  without  nitrogen,  whence  they  are 
sometimes  called  the  "  non-nitrogenous"  substances. 

1.  Staech  (Cj^HioOjo). — The  first  of  these  substances  seems  to 
form  an  exception  to  the  general  rule  In  a  very  important  particu- 
lar, viz.,  that  it  is  not  crystallizable.  Still,  since  it  so  closely 
resembles  the  rest  in  all  its  general  properties,  and  since  it  is  easily 
convertible  into  sugar,  which  is  itself  crystallizable,  it  is  naturally 
included  in  the  second  class  of  proximate  principles.  Though  not 
crystallizable,  furthermore,  it  still  assumes  a  distinct  form,  by 
which  it  differs  from  substances  that  are  altogether  amorphous. 

Starch  occurs  in  some  part  or  other  of  almost  all  the  flowering 
plants.  It  is  very  abundant  in  corn,  wheat,  rye,  oats,  and  rice,  in 
the  parenchyma  of  the  potato,  in  peas  and  beans,  and  in  most 
vegetable  substances  used  as  food.  It  constitutes  almost  entirely 
the  different  preparations  known  as  sago,  tapioca,  arrowroot,  &c., 
which  are  nothing  more  than  varieties  of  starch,  extracted  from 
different  species  of  plants. 

The  following  is  a  list  showing  the  percentage  of  starch  occurring 
in  different  kinds  of  food : — ' 

'  Pereira  on  Food  and  Diet,  New  York,  1843,  p.  39. 


80        PROXIMATE    PRINCIPLES    OF    THE    SECOND    CLASS. 


Quantity  of  Starch 

IN  100  PARTS  IN 

Rice 

.     85.07 

Wheat  flour   . 

.     56.50 

Maize 

.     80.92 

Iceland  moss 

.     44.60 

Barley  meal 

.     67.18 

Kidney  bean  . 

.     35.94 

Rye  meal 

.     61.07 

Peas 

.     32.45 

Oat  meal 

.     59.00 

Potato    . 

.     15.70 

Grain* s  of  Potato  Starch. 


When  purified  from  foreign  substances,  starch  is  a  white,  light 
powder,  which  gives  rise  to  a  peculiar  crackling  sensation  when 

rubbed  between  the  fingers. 
It  is  not  amorphous,  as  we 
have  already  stated,  but  is 
composed  of  solid  granules, 
which,  while  they  have  a 
general  resemblance  to  each 
other,  differ  somewhat  in  va- 
rious particulars.  The  starch 
grains  of  the  potato  (Fig.  2) 
vary  considerably  in  size. 
The  smallest  have  a  diameter 
of  ^^m,  the  largest  4^0  of 
an  inch.  They  are  irregu- 
larly pear-shaped  in  form, 
and  are  marked  by  concen- 
tric laminae,  as  if  the  matter 
of  which  they  are  composed  had  been  deposited  in  successive  layers. 
At  one  point  on  the  surface  of  every  starch  grain,  there  is  a  minute 

pore  or  depression,  called  the 
hilus,  around  which  the  cir- 
cular markings  are  arranged 
in  a  concentric  form. 

The  starch  granules  of 
arrowroot  (Fig.  8)  are  gene- 
rally smaller  and  more  uni- 
form in  size,  than  those  of 
the  potato.  They  vary  from 
20V0  to  5I0  of  an  inch  in 
diameter.  They  are  elongated 
and  cylindrical  in  form,  and 
the  concentric  markings  are 
less  distinct  than  in  the  pre- 
starch  GRAI.V.  OP  BEKiauDA  ARROWROOT.       ccdiug  varlcty.     The  hilus 


STARCH. 


81 


Staech  Grains  of  Wheat  Floub. 


has  here  sometimes  the  form  of  a  circular  pore,  and  sometimes  that 
of  a  transverse  fissure  or  slit. 

The  grains  of  wheat  starch  (Fig.  4)  are  still  smaller  than  those 
of  arrowroot.  They  vary 
from  T^-otru  to  ^y-J-Q-  of  an  inch 
in  diameter.  They  are 
nearly  circular  in  form,  with 
a  round  or  transverse  hilus, 
but  without  any  distinct 
appearance  of  lamination. 
Many  of  them  are  flattened 
or  compressed  laterally,  so 
that  they  present  a  broad 
surface  in  one  position,  and 
a  narrow  edge  when  viewed 
in  the  opposite  direction. 

The  starch  grains  of  In- 
dian corn  (Fig.  5)  are  of 
nearly  the  same  size  with 
those  of  wheat  flour.  They  are  somewhat  more  irregular  and 
angular  in  shape ;  and  are  often  marked  with  crossed  or  radiating 
lines,  as  if  from  partial  fracture. 

Starch   is   also  an  ingre-  Fig.  5. 

dient  of  the  animal  body. 
It  was  first  observed  by 
Purkinje,  and  afterward  by 
Kolliker,'  that  certain  bodies 
are  to  be  found  in  the  interior 
of  the  brain,  about  the  late- 
ral ventricles,  in  the  fornix, 
septum  lucidum  and  other 
parts,  which  present  a  cer- 
tain resemblance  to  starch 
grains,  and  which  have  there- 
fore been  called  "corpora 
amylacea."  Subsequently 
Virchow'  corroborated  the 
above  observations,  and  ascertained  the  corpora  amylacea  to  be 


Starch  Grains  of  Indian  Corn. 


'  Handbnch  der  Gewebelelire,  Leipzig,  1852,  p.  311. 
2  In  American  Journal  Med.  Sci.,  April,  1854,  p.  466. 


82 


PROXIMATE    PRINCIPLES    OF    THE    SECOND    CLASS. 


Fie.  6. 


Starch   Graixs    from    Wall    of    Lateral 
Vestricles;  frora  a  wouiuu  aired  3o. 


really  substances  of  a  starchy  nature ;  since  they  exhibit  the  usual 
chemical  reactions  of  vegetable  starch. 

The  starch  granules  of  the  human  brain  (Fig.  6)  are  transparent 

and  colorless,  like  those  from 
plants.  They  refract  the  light 
strongly,  and  vary  in  size 
from  4  J^^  to  TxV(7  of  an 
inch.  Their  average  is  ygVo 
of  an  inch.  They  are  some- 
times rounded  or  oval,  and 
sometimes  angular  in  shape. 
They  resemble  considerably 
in  appearance  the  starch 
granules  of  Indian  corn.  The 
largest  of  them  present  a 
very  faint  concentric  lamina- 
tion, but  the  greater  number 
are  destitute  of  any  such 
appearance.  They  have 
nearly  always  a  distinct  hilus,  which  is  sometimes  circular  and 
sometimes  slit-shaped.  They  are  also  often  marked  with  delicate 
radiating  lines  and  shadows.  On  the  addition  of  iodine,  they  become 
colored,  first  purple,  afterward  of  a  deep  blue.  They  are  less  firm 
in  consistency  than  vegetable  starch  grains,  and  can  be  more  readily 
disintegrated  by  pressing  or  rubbing  them  upon  the  glass. 

Starch,  derived  from  all  these  different  sources,  has,  so  far  as 
known,  the  same  chemical  composition,  and  may  be  recognized  by 
the  same  tests.  It  is  insoluble  in  cold  water,  but  in  boiling  water 
its  granules  first  swell,  become  gelatinous  and  opaline,  then  fuse 
with  each  other,  and  finally  liquefy  altogether,  provided  a  sufficient 
quantity  of  water  be  present.  After  that,  they  cannot  be  made  to 
resume  their  original  form,  but  on  cooling  and  drying  merely  solidify 
into  a  homogeneous  mass  or  paste,  more  or  less  consistent,  accord- 
ing to  the  quantity  of  water  which  remains  in  union  with  it.  The 
starch  is  then  said  to  be  amorphous  or  "  hydrated."  By  this  process 
it  is  not  essentially  altered  in  its  chemical  properties,  but  only  in 
its  physical  condition.  Whether  in  granules,  or  in  solution,  or  in 
an  amorphous  and  hydrated  state,  it  strikes  a  deep  blue  color  on 
the  addition  of  free  iodine. 

Starch  may  be  converted  into  sugar  by  three  different  methods. 
First,  by  boiling  with  a  dilute  acid.     If  starch  be  boiled  Avith  dilute 


SUGAR.  83 

nitric,  sulphuric,  or  muriatic  acid  during  thirty-six  hours,  it  first 
changes  its  opalescent  appearance,  and  becomes  colorless  and  trans- 
parent ;  losing  at  the  same  time  its  power  of  striking  a  blue  color 
with  iodine.  After  a  time,  it  begins  to  acquire  a  sweet  taste,  and 
is  finally  altogether  converted  into  a  peculiar  species  of  sugar. 

Secondly,  by  contact  with  certain  animal  and  vegetable  sub- 
stances. Thus,  boiled  starch  mixed  with  human  saliva  and  kept 
at  the  temperature  of  100°  F.,  is  converted  in  a  few  minutes  into 
sugar. 

Thirdly,  by  the  processes  of  nutrition  and  digestion  in  animals 
and  vegetables.  A  large  part  of  the  starch  stored  up  in  seeds  and 
other  vegetable  tissues  is,  at  some  period  or  other  of  the  growth  of 
the  plant,  converted  into  sugar  by  the  molecular  changes  going  on 
in  the  vegetable  febric.  It  is  in  this  way,  so  far  as  we  know,  that 
'  all  the  sugar  derived  from  vegetable  sources  has  its  origin. 

Starch,  as  a  proximate  principle,  is  more  especially  important  as 
entering  largely  into  the  composition  of  many  kinds  of  vegetable 
food.  With  these  it  is  introduced  into  the  alimentary  canal,  and 
there,  during  the  process  of  digestion,  is  converted  into  sugar. 
Consequently,  it  does  not  appear  in  the  blood,  nor  in  any  of  the 
secreted  fluids, 

2.  SuGAE. — This  group  of  proximate  principles  includes  a  con- 
siderable number  of  substances,  which  -differ  in  certain  minor 
details,  while  they  resemble  each  other  in  the  following  particulars : 
They  are  readily  soluble  in  water,  and  crystallize  more  or  less 
perfectly  on  evaporation ;  they  have  a  distinct  sweet  taste ;  and 
finally,  by  the  process  of  fermentation,  they  are  converted  into 
alcohol  and  carbonic  acid. 

These  substances  are  derived  from  both  animal  and  vegetable 

sources.     Those  varieties  of  sugar  which  are  most  familiar  to  us 

are  the  following  six,  three  of  which  are  of  vegetable  and  three  of 

animal  origin. 

rCaive  sugar,                                           .  r  Milk  sugar, 

Vegetab^         r,          Animal  y  • 

°               -j  Grrape  stigar,  J.  Liver  sugar, 

sugars.       ( gj^g^j.  ^^  starch.  sugars.  (  ^^^^^^  ^^  1x0^^^^^. 

The  cane  and  grape  sugars  are  held  in  solution  in  the  juices  of 
the  plants  from  which  they  derive  their  name.  Sugar  of  starch,  or 
glucose,  is  produced  by  boiling  starch  for  a  long  time  with  a  dilute 
acid.  Liver  sugar  and  sugar  of  milk  are  produced  in  the 
tissues  of  the  liver  anc^  the   mammary  gland,  and  the   sugar  of 


84:        PROXIMATE    PRINCIPLES    OF    THE    SECOXD    CLASS. 

honey  is  prepared  in  some  way  bj  the  bee  from  materials  of  vege- 
table origin. 

These  varieties  differ  but  little  in  their  ultimate  chemical  compo- 
sition. The  following  formulae  have  been  established  for  three  of 
them. 

Cane  sugar      .         .         ^        .         .         ,     ^  Cj^HjjOja 
Milk  su£;ar ==  C,,H„0, 


24*^24^24 


Glucose  .......=  C,,H,„0, 


24  "28^23 


Cane  sugar  is  sweeter  than  most  of  the  other  varieties,  and  more 
soluble  in  water.  Some  sugars,  such  as  liver  sugar  and  sugar  of 
honey,  crystallize  only  with  great  difficulty ;  but  this  is  probably 
owing  to  their  being  mingled  with  other  substances,  from  which  it 
is  difficult  to  separate  them  completely.  If  they  could  be  obtained 
in  a  state  of  purity,  they  would  doubtless  crystallize  as  perfectly  as 
cane  sugar.  The  different  sugars  vary  also  in  the  readiness  with 
which  they  undergo  fermentation.  Some  of  them,  as  grape  sugar 
and  liver  sugar,  enter  into  fermentation  very  promptly ;  others, 
such  as  milk  and  cane  sugar,  with  considerable  difficulty. 

The  above  are  not  to  be  regarded  as  the  only  varieties  of  sugar 
existing  in  nature.  On  the  contrary,  it  is  probable  that  nearly 
every  different  species  of  animal  and  vegetable  produces  a  distinct 
kind  of  sugar,  differing  slightly  from  the  rest  in  its  degree  of  sweet- 
ness, its  solubility,  its  crystallization,  its  aptitude  for  fermentation, 
and  perhaps  in  its  elementary  composition.  Nevertheless,  there  is 
so  close  a  resemblance  between  them  that  they  are  all  properly 
regarded  as  belonging  to  a  single  group. 

The  test  most  commonly  employed  for  detecting  the  presence  of 
sugar  is  that  known  as  Trommer's  test.  It  depends  upon  the  fact 
that  the  saccharine  substances  have  the  power  of  reducing  the 
persalts  of  copper  when  heated  with  them  in  an  alkaline  solution. 
The  test  is  applied  in  the  following  manner :  A  very  small  quantity 
of  sulphate  of  copper  in  solution  should  be  added  to  the  suspected 
liquid,  and  the  mixture  then  rendered  distinctly  alkaline  by  the 
addition  of  caustic  potassa.  The  Avhole  solution  then  takes  a  deep 
blue  color.  On  boiling  the  mixture,  if  sugar  be  present,  the  in- 
soluble suboxide  of  copper  is  thrown  down  as  an  opaque  red, 
yellow,  or  orange- colored  deposit;  otherwise  no  change  of  color 
takes  place. 

This  test  requires  some  precautions  in  its  application.  In  the 
first  place,  it  is  not  applicable  to  all  varieties  of  sugar.  Cane 
sugar,  for  example,  when  pure,  has  no  power  of  reducing  the  salts 


SUGAE.  85 

of  copper,  even  when  present  in  large  quantity.  Maple  sugar,  also, 
which  resembles  cane  sugar  in  some  other  respects,  reduces  the 
copper,  in  Trommer's  test,  but  slowly  and  imperfectly.  Beet-root 
sugar,  according  to  Bernard,  presents  the  same  peculiarity.  If 
these  sugars,  however,  be  boiled  for  two  or  three  minutes  with  a 
trace  of  sulphuric  acid,  they  become  converted  into  glucose,  and 
acquire  the  power  of  reducing  the  salts  of  copper.  Milk  sugar, 
liver  sugar,  and  sugar  of  honey,  as  well  as  grape  sugar  and  glucose, 
all  act  promptly  and  perfectly  with  Trommer's  test  in  their  natural 
condition. 

Secondly,  care  must  be  taken  to  add  to  the  suspected  liquid  only 
a  small  quantity  of  sulphate  of  copper,  just  sufiicient  to  give  to  the 
whole  a  distinct  blue  tinge,  after  the  addition  of  the  alkali.  If  a 
larger  quantity  of  the  copper  salt  be  used,  the  sugar  in  solution 
may  not  be  sufficient  to  reduce  the  whole  of  it ;  and  that  which 
remains  as  a  blue  sulphate  will  mask  the  yellow  color  of  the  sub- 
oxide thrown  down  as  a  deposit.  By  a  little  care,  however,  in 
managing  the  test,  this  source  of  error  may  be  readily  avoided. 

Thirdly,  there  are  some  albuminous  substances  which  have  the 
power  of  interfering  with  Trommer's  test,  and  prevent  the  reduc- 
tion of  the  copper  even  when  sugar  is  present.  Certain  animal 
matters,  to  be  more  particularly  described  hereafter,  which  are 
liable  to  be  held  in  solution  in  the  gastric  juice,  have  this  effect. 
This  source  of  error  may  be  avoided,  and  the  substances  in  ques- 
tion eliminated  when  present,  by  treating  the  suspected  fluid  with 
animal  charcoal,  or  by  evaporating  and  extracting  it  with  alcohol 
before  the  application  of  the  test. 

A  less  convenient  but  somewhat  more  certain  test  for  sugar  is 
that  of  fermentation.  The  saccharine  fluid  is  mixed  with  a  little 
yeast,  and  kept  at  a  temperature  of  70°  to  100°  F.  until  the  fer- 
menting process  is  completed.  By  this  process,  as  already  men- 
tioned, the  sugar  is  converted  into  alcohol  and  carbonic  acid.  The 
gas,  which  is  given  off  in  minute  bubbles  during  fermentation, 
should  be  collected  and  examined.  The  remaining  fluid  is  purified 
by  distillation  and  also  subjected  to  examination.  If  the  gas  be 
found  to  be  carbonic  acid,  and  the  remaining  fluid  contain  alcohol, 
there  can  be  no  doubt  that  sugar  was  present  at  the  commencement 
of  the  operation. 

The  following  list  shows  the  percentage  of  sugar  in  various 
articles  of  food.' 

'  Pereira,  op.  cit.,  p.  55. 


86 


PROXIMATE    PRINCIPLES    OF    THE    SECOND    CLASS. 


62.50 

Wheat  flour , 

4. 20  to  8.48 

18.12 

Rye  meal 

3.28 

16.48 

Indian  meal 

1.45 

12.50 

Peas 

2.00 

11.52 

Cow's  milk  . 

4.77 

9.00 

Ass's  milk    . 

6.08 

6.00 

Human  milk 

6.50 

5.21 

Quantity  of  Sugar  in  100  parts  ix 
Figs 
Cherries 
Peaches 
Tamarinds 
Pears 
Beets 

Sweet  almonds 
Barley  meal    . 

Besides  the  sugar,  therefore,  whicli  is  taken  into  the  alimentary- 
canal  in  a  pure  form,  a  large  quantity  is  also  introduced  as  an  in- 
gredient of  the  sweet-flavored  fruits  and  vegetables.  All  the 
starchy  substances  of  the  food  are  also  converted  into  sugar  in  the 
process  of  digestion.  Two  of  the  varieties  of  sugar,  at  least, 
originate  in  the  interior  of  the  body,  viz.,  sugar  of  milk  and  liver 
sugar.  The  former  exists  in  a  solid  form  in  the  substance  of  the 
mammary  gland,  from  which  it  passes  in  solution  into  the  milk. 
The  liver  sugar  is  found  in  the  substance  of  the  liver,  and  almost 
always  also  in  the  blood  of  the  hepatic  veins.  The  sugar  which  is 
introduced  with  the  food,  as  well  as  that  which  is  formed  in  the 
liver,  disappears  by  decomposition  in  the  animal  fluids,  and  does 
not  appear  in  any  of  the  excretions. 


8.  Fats. — These  substances,  like  the  sugars,  are  derived  from 
both  animal  and  vegetable  sources.  There  are  three  principal 
varieties  of  them,  which  may  be  considered  as  representing  the 
class,  viz : — 

Oleine =^94  ^sr  ^15 

Margarine         ......=  C.g  H^j  0,2 

Stearine =  Ci^jHi^iO,^ 

The  principal  difference  between  the  oleaginous  and  saccharine 
substances,  so  far  as  regards  their  ultimate  chemical  composition, 
is  that  in  the  sugars  the  oxygen  and  hydrogen  always  exist  together 
in  the  proportion  to  form  water ;  while  in  the  fats  the  proportions  of 
carbon  and  hydrogen  are  nearly  the  same,  but  that  of  oxygen  is 
considerably  less.  The  fats  are  all  fluid  at  a  high  temperature,  but 
assume  the  solid  form  on  cooling.  Stearine,  which  is  the  most 
solid  of  the  three,  liquefies  only  at  143"^  F. ;  margarine  at  118°  F. ; 
while  oleine  remains  fluid  considerably  below  100°  F.,  and  even 
very  near  the  freezing  point  of  water.  The  fats  are  all  insoluble 
in  water,  but  readily  soluble  in  ether.  By  prolonged  boiling  in 
water  with  a  caustic  alkali,  they  are  decomposed,  and  as  the  result  of 
the  decomposition  there  are  formed  two  new  bodies ;  first,  glycerine, 


FATS. 


87 


•wliicli  is  a  neutral  fluid  substance,  and  secondly,  a  fatty  acid,  viz : 
oleic,  rnargaric,  or  stearic  acid,  corresponding  to  the  kind  of  fat 
which  has  been  used  in  the  experiment.     The  glycerine  remains  in 
a  free  state,  while  the  fatty  acid  unites  with  the  alkali  employed, 
forming  an  oleate,  margarate,  or  stearate.     This   combination   is 
termed  a  soap,  and  the  process  by  which  it   is  formed  is  called 
saponification.     This  process,  however,  is  not  a  simple  decomposition 
of  the  fatty  body,  since  it  can  only  take  place  in  the  presence  of 
water;  several  equivalents  of  which  unite  with  the  elements  of  the 
fatty  body,  and  enter  into  the  composition  of  the  glycerine,  &c.,  so 
that  the  fatty  acid  and  the  glycerine  together  weigh  more  than  the 
original  fatty  substance  which  was  decomposed.     It  is  not  proper, 
therefore,  to  regard  an  oleaginous  body  as  formed  by  the  union  of  a 
fatty  acid  with  glycerine.     It  is  formed,  on  the  contrary,  in  all  pro- 
bability, by  the  direct  combination  of  its  ultimate  chemical  elements. 
The  different  kinds  of  oil,  fat,  lard,  suet,  &c.,  contain  the  three 
oleaginous  matters  mentioned  above,  mingled  together  in  different 
proportions.       The   more  solid  fats  contain  a  larger   quantity  of 
stearine  and  margarine ;  the  less  consistent  varieties,  a  larger  pro- 
portion of  oleine.       Neither   of  the  oleaginous  matters,  stearine, 
margarine,  or  oleine,  ever  occur  separately ;  but  in  every  fatty  sub- 
stance they  are  mingled  together,  so  that  the  more  fluid  of  them  hold 
in  solution  the  more  solid. 

Generally  speaking,  in  the  ^^'  *' 

living  body,  these  mixtures 
are  fluid,  or  nearly  so ;  for 
though  both  stearine  and 
margarine  are  solid,  when 
pure,  at  the  ordinary  tem- 
perature of  the  body,  they 
are  held  in  solution,  during 
life,  by  the  oleine  with  wh  ich 
they  are  associated.  After 
death,  however,  as  the  body 
cools,  the  stearine  and  mar- 
garine sometimes  separate 
from  the  mixture  in  a  crys- 
talline form,  since  the  oleine 
can  no  longer  hold  in  solu- 
tion so  large  a  quantity  of  them  as  it  had  dissolved  at  a  higher 
temperature. 


Stearin  B  ciystallized  from  a  Warm    Solution  in 
Oleine. 


88 


PROXIMATE    PRINCIPLES    OF    THE    SECOND    CLASS. 


Fig.  8. 


These  substances  crystallize  in  very  slender  needles,  which  are 
sometimes  straight,  but  more  often  somewhat  curved  or  wavy  in 
their  outline.  (Fig.  7.) 

They  are  always  deposited  in  a  more  or  less  radiated  form ;  and 
have  sometimes  a  very  elegant,  branched,  or  arborescent  arrange- 
ment. 

"When  in  a  fluid  state,  the  fatty  substances  present  themselves 

under  the  form  of  drops  or 
globules,  which  vary  indefi- 
nitely in  size,  but  which 
may  be  readily  recognized 
by  their  optical  properties. 
They  are  circular  in  shape, 
and  have  a  faint  amber  color, 
distinct  in  the  larger  globules, 
less  so  in  the  smaller.  They 
have  a  sharp,  well  defined 
outline  (Fig.  8) ;  and  as  they 
refract  the  light  strongly, 
and  act  therefore  as  double 
convex  lenses,  they  present 
a  brilliant  centre,  surrounded 
by  a  dark  border.  These 
marks  will  generally  be 
sufficient  to  distinguish  them  under  the  microscope. 

The  following  list  shows  the  percentage  of  oily  matter  present  in 
various  kinds  of  animal  and  vegetable  food.' 

Quantity  of  Fat  in  100  pakts  in 


Oleaginous   Principles   of   Human    Fat. 
Stearine  and  Margarine  crystallized  ;  Oleine  fluid. 


Filberts  . 

.     60.00 

Ordinary  meat 

.     14.30 

Walnuts 

.     50.00 

Liver  of  the  ox 

.       3.89 

Cocoa-nuts 

.     47.00 

Cow's  milk    . 

.       3.13 

Olives     . 

.     32.00 

Human  milk 

.       3.55 

Linseed 

.     22.00 

Asses'  milk  . 

.       0.11 

Indian  Corn    . 

.       9.00 

Goats'  milk   . 

.       3.32 

Yolk  of  eggs   . 

.     28.00 

The  oleaginous  matters  present  a  striking  peculiarity  as  to  the 
form  under  which  they  exist  in  the  animal  body;  a  peculiarity 
which  distinguishes  them  from  all  the  other  proximate  principles. 
The  rest  of  the  proximate  principles  are  all  intimately  associated 
together  by  molecular  union,  so  as  to  form  either  clear  solutions  or 


'  Pereira,  op.  cit.,  p.  81. 


FATS.  89 

homogeneous  solids.  Thus,  the  sugars  of  the  blood  are  in  solution 
in  water,  in  company  with  the  albumen,  the  phosphate  of  lime, 
chloride  of  sodium,  and  the  like ;  all  of  them  equally  distributed 
throughout  the  entire  mass  of  the  fluid.  In  the  bones  and  car- 
tilages, the  animal  matters  and  the  calcareous  salts  are  in  similarly 
intimate  union  with  each  other;  and  in  every  other  part  of  the 
body  the  animal  and  inorganic  ingredients  are  united  in  the  same 
way.  But  it  is  different  with  the  fats.  For,  while  the  three  prin- 
cipal varieties  of  oleaginous  matter  are  always  united  with  each 
other,  they  are  not  united  with  any  of  the  other  kinds  of  proximate 
principles;  that  is,  with  water,  saline  substances,  sugars,  or  albu- 
minous matters.  Almost  the  only  exception  to  this  is  in  the  nerv- 
ous tissue;  in  which,  according  to  Eobin  and  Yerdeil,  the  oily 
matters  seem  to  be  united  with  an  albuminoid  substance.  Another 
exception  is,  perhaps,  in  the  bile ;  since  some  of  the  biliary  salts 
have  the  power  of  dissolving  a  certain  quantity  of  fat.  Every- 
where else,  instead  of  forming  a  homogeneous  solid  or  fluid  w^ith 
the  other  proximate  principles,  the  oleaginous  matters  are  found 
in  distinct  masses  or  globules,  which  are  suspended  in  serous  fluids, 
interposed  in  the  interstices  between  the  anatomical  elements,  in- 
cluded in  the  interior  of  cells,  or  deposited  in  the  substance  of 
fibres  or  membranes.  Even  in  the  vegetable  tissues,  the  oil  is 
always  deposited  in  this  manner  in  distinct  drops  or  granules. 

Owing  to  this  fact,  the  oils  can  be  easily  extracted  from  the 
organized  tissues  by  the  employment  of  simply  mechanical  pro- 
cesses. The  tissues,  animal  or  vegetable,  are  merely  cut  into  small 
pieces  and  subjected  to  pressure,  by  which  the  oil  is  forced  out 
from  the  parts  in  which  it  was  entangled,  and  separated,  without 
any  further  manipulation,  in  a  state  of  purity.  A  moderately 
elevated  temperature  facilitates  the  operation  by  increasing  the 
fluidity  of  the  oleaginous  matter ;  but  no  other  chemical  agency  is 
required  for  its  separation.  Under  the  microscope,  also,  the  oil- 
drops  and  granules  can  be  readily  perceived  and  distinguished 
from  the  remaining  parts  of  the  tissue,  and  can,  moreover,  be 
easily  recognized  by  the  dissolving  action  of  ether,  which  acts 
upon  them,  as  a  general  rule,  without  attacking  the  other  proxi- 
mate principles. 

Oils  are  found,  in  the  animal  body,  most  abundantly  in  the 
adipose  tissue.  Here  they  are  contained  in  the  interior  of  the 
adipose  vesicles,  the  cavities  of  which  they  entirely  fill,  in  a  state 


90         PEOXIMATE    PRINCIPLES    OF    THE    SECOND    CLASS. 


Hdman  Adiposk  Tissue. 


of  health.     These  vesicles  are  transparent,  and  have  a  somewhat 
angular  form,  owing  to  their  mutual  compression.  (Fig.  9.)     They 

vary  in  diameter,  in  the  hu- 
~'  ' '  man  subject,  from  p^ts  to  j^^- 

of  an  inch,  and  are  composed 
of  a  thin,  structureless  ani- 
mal membrane,  forming  a 
closed  sac,  in  the  interior  of 
which  the  oily  matter  is  con- 
tained. There  is  here,  accord- 
ingly, no  union  whatever  of 
the  oil  with  the  other  proxi- 
mate principles,  but  only  a 
mechanical  inclusion  of  it  in 
the  interior  of  the  vesicles. 
Sometimes,  when  emaciation 
is  going  on,  the  oil  partially 
disappears  from  the  cavity  of 
the  adipose  vesicle,  and  its  place  is  taken  by  a  watery  serum ;  but 
the  serous  and  oily  fluids  always  remain  distinct,  and  occupy  differ- 
ent parts  of  the  cavity  of  the  vesicle. 

In  the  chyle,  the  oleaginous  matter  is  in  a  state  of  emulsion  or 
suspension  ■  in  the  form  of  minute  particles  in  a  serous  fluid.     Its 

subdivision  is  here  more  com- 
Fig.  10.  plete,  and  its  molecules  more 

minute,  than  anywhere  else 
in  the  body.  It  presents  the 
appearance  of  a  fine  granular 
dust,  which  has  been  known 
by  the  name  of  the  "molecu- 
lar base  of  the  chyle."  A 
few  of  these  granules  are  to 
be  seen  which  measiire  jtt^tjo- 
of  an  inch  in  diameter ;  but 
they  are  generally  much  less 
than  this,  and  the  greater  part 
are  so  small  that  they  cannot 
be  accurately  measured.  (Fig. 
10.)  For  the  same  reason 
they  do  not  present  the  bril- 
liant centre  and  dark  border  of  the  larger  oil-globules ;  but  appear 


Chtle,    from    commencernent  of    Thoracic   Dnct, 
fiom  tbe  Dog. 


FATS. 


91 


by  transmitted  light  only  as  minute  dark  granules.     The  white 

color  and  opacity  of  the   chyle,  as  of  all  other  fatty  emulsions. 

depend  upon  this  molecular  condition  of  the  oily  ingredients.    The 

albumen,  salts,  &c.,  which  are  in  intimate  union  with  each  other, 

and  in  solution  in  the  water,  would  alone  make  a  colorless  and 

transparent  fluid;  but  the  oily  matters,  suspended  in  distinct  par- 

tides,  which  have  a  different  refractive  power  from  the  serous  fluid, 

interfere  with  its  transparency 

and  give  it  the  white  color  and  ^^^'  ^^' 

opaque  appearance  which  are 

characteristic    of    emulsions. 

The  oleaginous  nature  of  these 

particles  is  readily  shown  by 

their  solubility  in  ether. 

In  the  milk,  the  oily  matter 
occurs  in  larger  masses  than 
in  the  chyle.  In  cow's  milk 
(Fig.  11),  these  oil-drops,  or 
"milk-globules,"  are  not  quite 
fluid,  but  have  a  pasty  con- 
sistency, owing  to  the  large 
quantity  of  margarine  which 
they  contain,  in  proportion  to 

the  oleine.  When  forcibly  amalgamated  with  each  other  and 
collected  into  a  mass  by  prolonged  beating  or  churning,  they  con- 
stitute butter.    In  cow's  milk. 


Globules  of  Cow's  Mii.k. 


the  globules  vary  somewhat 
in  size,  but  their  average 
diameter  is  4oVtf  of  ^^  inch. 
They  are  simply  suspended 
in  the  serous  fluid  of  the 
milk,  and  are  not  covered 
with  any  albuminous  mem- 
brane. 

In  the  cells  of  the  laryn- 
geal, tracheal,  and  costal  car- 
tilages (Fig.  12),  there  is 
always  more  or  less  fat  de- 
posited in  the  form  of  rounded 
globules,  somewhat  similar  to 
those  of  the  milk. 


Fig.  12. 


Cells  op  Costal  C  akti  l  ao  es,  coutainiug  Oil 
GlobaIe».    Uumau. 


92 


PROXIMATE    PRINCIPLES    OF    THE    SECOND    CLASS. 


Hepatic  C  ELLS.    Human. 


In  the  glandular  cells  of  the  liver,  oil  occurs  constantly,  in  a 

state  of  health.     It  is  here  deposited  in  the  substance  of  the  cell 

(Fig.13),  generally  in  smaller 
^'S'  ^^'  globules  than  the  preceding. 

In  some  cases  of  disease,  it 
accumulates  in  excessive 
quantity,  and  produces  the 
state  known  as  fatty  degene- 
ration of  the  liver.  This  is 
consequently  only  an  ex- 
aggerated condition  of  that 
which  normally  exists  in 
health. 

In  the  carnivorous  animals 
oil  exists  in  considerable 
quantity  in  the  convoluted 
portion  of  the  uriniferous 
tubules.  (Fig.  14.)  It  is  here 

in  the  form  of  granules  and  rounded  drops,  which  sometimes  appear 

to  fill  nearly  the  whole  calibre  of  the  tubules. 

It  is  found  also  in  the  secreting  cells  of  the  sebaceous  and  other 

glandules,  deposited  in  the 
^'S-  ■^^"  same  manner  as  in  those  of 

the  liver,  but  in  smaller 
quantity.  It  exists,  beside, 
in  large  proportion,  in  a 
granular  form,  in  the  secre- 
tion of  the  sebaceous  gland- 
ules. 

It  occurs  abundantly  in 
the  marrow  of  the  bones, 
both  under  the  form  of  free 
oil-globules  and  inclosed  in 
the  vesicles  of  adipose  tissue. 
It  is  found  in  considerable 
quantity  in  the  substance  of 
the  yellow  wall  of  the  corpus 
luteum,  and  is  the  immediate 

cause  of  the  peculiar  color  of  this  body. 

It  occurs  also  in   the  form  of  granules  and  oil-drops  in  the 

muscular  fibres  of  the  uterus  (Fig.  15),  in  which  it  begins  to  be 


Uriniferous  Tobules  of  Dog,  from  Cortical 
Portion  of  Kidney. 


FATS. 


93 


MtTsctTLAR  FiBRKS  OF  HuMAN  Utekcs,  three 
weeks  after  parturition. 


deposited  soon  after  delivery,  and  where  it  continues  to  be  present 
during  the  whole  period  of  the  resorption  or  involution  of  this  organ. 

In  all  these  instances,  the  oleaginous  matters  remain  distinct  in 
form  and  situation  from  the 
other  ingredients  of  the  ani- 
mal frame,  and  are  only  me- 
chanically entangled  among 
its  fibres  and  cells,  or  im- 
bedded separately  in  their 
interior. 

A  large  part  of  the  fat 
which  is  found  in  the  body 
may  be  accounted  for  by  that 
which  is  taken  in  with  the 
food,  since  oily  matter  occurs 
in  both  animal  and  vegetable 
substances.  Fat  is,  however, 
formed  in  the  body,  independ- 
ently of  what  is  introduced 
with  the  food.  This  im- 
portant fact  has  been  definitely  ascertained  by  the  experiments  of 
MM.  Dumas  and  Milne-Edwards  on  bees,'  M.  Persoz  on  geese,^  and 
finally  by  those  of  M.  Boussingault  on  geese,  ducks,  and  pigs.'  The 
observers  first  ascertained  the  quantity  of  fat  existing  in  the  whole 
body  at  the  commencement  of  the  experiment.  The  animals  were 
then  subjected  to  a  definite  nutritious  regimen,  in  which  the 
quantity  of  fatty  matter  was  duly  ascertained  by  analysis.  The 
experiments  lasted  for  a  period  varying,  in  difi'erent  instances,  from 
thirty-one  days  to  eight  months;  after  which  the  animals  were 
killed  and  all  their  tissues  examined.  The  result  of  these  investi- 
gations showed  that  considerably  more  fat  had  been  accumulated 
by  the  animal  during  the  course  of  the  experiment  than  could  be 
accounted  for  by  that  which  existed  in  the  food ;  and  placed  it 
beyond  a  doubt  that  oleaginous  substances  may  be,  and  actually 
are,  formed  in  the  interior  of  the  animal  body  by  the  decomposition 
or  metamorphosis  of  other  proximate  principles. 

It  is  not  known  from  what  proximate  principles  the  fat  is  pro- 
duced, when  it  originates  in  this  way  in  the  interior  of  the  body. 
Particular  kinds  of  food  certainly  favor  its  production  and  accu- 


Annales  de  Chim.  et  de  Phys.,  3d  series,  vol.  xiv.  p.  400.  ^  Ibid.,  p.  408. 

Cbiraie  Agricole,  Paris,  1854. 


94         PROXIMATE    PRINCIPLES    OF    THE    SECOND    CLASS. 

mulation  to  a  considerable  degree.  It  is  well  known,  for  instance, 
that  in  sugar-growing  countries,  as  in  Louisiana  and  the  West 
Indies,  during  the  few  weeks  occupied  in  gathering  the  cane  and 
extracting  the  sugar,  all  the  negroes  employed  on  the  plantations, 
and  even  the  horses  and  cattle,  that  are  allowed  to  feed  freely  on 
the  saccharine  juices,  grow  remarkably  fat;  and  that  they  again  lose 
their  superabundant  flesh  when  the  season  is  past.  Even  in  these 
instances,  however,  it  is  not  certain  whether  the  saccharine  substances 
are  directly  converted  into  fat,  or  whether  they  are  first  assimilated 
and  only  afterward  supply  the  materials  for  its  production.  The 
abundant  accumulation  of  fat  in  certain  regions  of  the  body,  and  its 
absence  in  others ;  and  more  particularly  its  constant  occurrence  in 
certain  situations  to  which  it  could  not  be  transported  by  the  blood, 
as  for  example  the  interior  of  the  cells  of  the  costal  cartilages,  the 
substance  of  the  muscular  fibres  of  the  uterus  after  parturition,  &c., 
make  it  probable  that  under  ordinary  conditions  the  oily  matter  is 
formed  by  decomposition  of  the  tissues  upon  the  very  spot  where 
it  subsequently  makes  its  appearance. 

In  the  female  during  lactation  a  large  part  of  the  oily  matter 
introduced  with  the  food,  or  formed  in  the  body,  is  discharged  with 
the  milk,  and  goes  to  the  support  of  the  infant.  But  in  the  female 
in  the  intervals  of  lactation,  and  in  the  male  at  all  times,  the  oily 
matters  almost  entirely  disappear  by  decomposition  in  the  interior 
of  the  body;  since  the  small  quantity  which  is  discharged  with  the 
sebaceous  matter  by  the  skin  bears  only  an  insignificant  proportion 
to  that  which  is  introduced  daily  with  the  food. 

The  most  important  characteristic,  in  a  physiological  point  of 
view,  of  the  proximate  principles  of  the  second  class,  relates  to  their 
origin  and  their  final  destination.  Not  only  are  they  all  of  a  purely 
organic  origin,  making  their  appearance  first  in  the  interior  of  vege- 
tables ;  but  the  sugars  and  the  oils  are  formed  also,  to  a  certain  ex- 
tent, in  the  bodies  of  animals ;  continuing  to  make  their  appearance 
-when  no  similar  substances,  or  only  an  insufficient  quantity  of  them, 
have  been  taken  with  the  food.  Furthermore,  when  introduced 
with  the  food,  or  formed  in  the  body  and  deposited  in  the  tissues, 
these  substances  do  not  reappear  in  the  secretions.  They,  therefore, 
for  the  most  part  disappear  by  decomposition  in  the  interior  of  the 
body.  They  pass  through  a  series  of  changes  by  which  their  es- 
sential characters  are  destroyed ;  and  they  are  finally  replaced  in 
the  circulation  by  other  substances,  which  are  discharged  with  the 
excreted  fluids. 


PROXIMATE    PRINCIPLES    OF    THE    THIRD    CLASS.  95 


CHAPTER    IV. 

PROXIMATE  PRINCIPLES  OF  THE  THIRD  CLASS. 

The  substances  belonging  to  this  class  are  very  important,  and 
form  by  far  tbe  greater  part  of  the  entire  mass  of  the  body.  They 
are  derived  both  from  animal  and  vegetable  sources.  They  have 
been  known  by  the  name  of  the  "protein  compounds"  and  the 
"  albuminoid  substances."  The  name  organic  substances  was  given 
to  them  by  Robin  and  Verdeil,  by  whom  their  distinguishing  pro- 
perties were  first  accurately  described.  They  have  not  only  an 
organic  origin,  in  common  with  the  proximate  principles  of  the 
second  class,  but  their  chemical  constitution,  their  physical  struc- 
ture and  characters,  and  the  changes  which  they  undergo,  are  all  so 
different  from  those  met  with  in  any  other  class,  that  the  term  "  or- 
ganic substances"  proper  appears  particularly  appropriate  to  them. 

Their  first  peculiarity  is  that  they  are  not  crystallizable.  They 
always,  when  pure,  assume  an  amorphous  condition,  which  is  some- 
times solid  (organic  substance  of  the  bones),  sometimes  fluid  (albu- 
men of  the  blood),  and  sometimes  semi-solid  in  consistency,  midway 
between  the  solid  and  fluid  condition  (organic  substance  of  the 
muscular  fibre). 

Their  chemical  constitution  differs  from  that  of  bodies  of  the 
second  class,  first  in  the  fact  that  they  all  contain  the  four  chemical 
elements,  oxygen,  hydrogen,  carbon,  and  nitrogen;  while  the 
starches,  sugars,  and  oils  are  destitute  of  the  last  named  ingredient. 
The  organic  matters  have  therefore  been  sometimes  known  by  the 
name  of  the  "  nitrogenous  substances,"  while  the  sugars,  starch,  and 
oils  have  been  called  "  non-nitrogenous."  Some  of  the  organic  mat- 
ters, viz.,  albumen,  fibrin,  and  casein,  contain  sulphur  also,  as  an  in- 
gredient ;  and  others,  viz.,  the  coloring  matters,  contain  iron.  The 
remainder  consist  of  oxygen,  hydrogen,  carbon,  and  nitrogen  alone. 

The  most  important  peculiarity,  however,  of  the  organic  sub- 
stances, relating  to  their  chemical  composition,  is  that  it  is  not 
definite.  That  is  to  say,  they  do  not  always  contain  precisely  the 
same  proportions  of  oxygen,  hydrogen,  carbon,  and  nitrogen ;  but 


96  PROXIMATE    PRINCIPLES    OF    THE    THIRD    CLASS. 

tlie  relative  quantities  of  these  elements  vary  within  certain  limits, 
in  different  individuals  and  at  different  times,  without  modifying,  in 
any  essential  degree,  the  peculiar  properties  of  the  animal  matters 
which  they  constitute.  This  fact  is  altogether  a  special  one,  and 
characteristic  of  organic  substances.  Ko  substance  having  a  definite 
chemical  composition,  like  phosphate  of  lime,  starch,  or  olein,  can 
suffer  the  slightest  change  in  its  ultimate  constitution  without  being, 
by  that  fact  alone,  totally  altered  in  its  essential  properties.  If 
phosphate  of  lime,  for  example,  were  to  lose  one  or  two  equivalents 
of  oxygen,  an  entire  destruction  of  the  salt  would  necessarily  result, 
and  it  would  cease  to  be  phosphate  of  lime.  For  its  properties  as  a 
salt  depend  entirely  upon  its  ultimate  chemical  constitution ;  and  if 
the  latter  be  changed  in  any  way,  the  former  are  necessarily  lost. 

But  the  properties  which  distinguish  the  organic  substances,  and 
which  make  them  important  as  ingredients  of  the  body,  do  not 
depend  immediately  upon  their  ultimate  chemical  constitution,  and 
are  of  a  peculiar  character ;  being  such  as  are  only  manifested  in 
the  interior  of  the  living  organism.  Albumen,  therefore,  though 
it  may  contain  a  few  equivalents  more  or  less  of  oxygen  or  nitrogen, 
does  not  on  that  account  cease  to  be  albumen,  so  long  as  it  retains 
its  fluidity  and  its  aptitude  for  undergoing  the  processes  of  absorp- 
tion and  transformation,  which  characterize  it  as  an  ingredient  of 
the  living  body. 

It  is  for  this  reason  that  considerable  discrepancy  has  existed  at 
various  times  among  chemists  as  to  the  real  ultimate  composition 
of  these  substances,  different  experimenters  often  obtaining  differ- 
ent analytical  results.  This  is  not  owing  to  any  inaccuracy  in  the 
analyses,  but  to  the  fact  that  the  organic  substance  itself  really  has 
a  different  ultimate  constitution  at  different  times.  The  most  ap- 
proved formulse  are  those  which  have  been  established  by  Liebig 
for  the  following  substances : — 

Fibrin    ..,...=  CjgJIjzgN^^OgjSj 

Albumen =  CjigHiggNj^OggSj 

Casein =  C^gsHjjsNaeOgoSj 

Owing  to  the  above  mentioned  variations,  however,  the  same 
degree  of  importance  does  not  attach  to  the  quantitative  ultimate 
analysis  of  an  organic  matter,  as  to  that  of  other  substances. 

This  absence  of  a  definite  chemical  constitution  in  the  organic  sub- 
stances is  undoubtedly  connected  with  their  incapacity  for  crystalli- 
zation. It  is  also  connected  with  another  almost  equally  peculiar 
fact,  viz.,  that  although  the  organic  substances  unite  with  acids  and 


ORGANIC    SUBSTANCES.  97 

with  alkalies,  they  do  not  play  the  part  of  an  acid  towards  the  base, 
or  of  a  base  towards  the  acid  ;  for  the  acid  or  alkaline  reaction  of 
the  substance  employed  is  not  neutralized,  but  remains  as  strong 
after  the  combination  as  before.  Futhermore,  the  union  does  not 
take  place,  so  far  as  can  be  ascertained,  in  any  definite  proportions. 
The  organic  substances  have,  in  fact,  no  combining  equivalent ;  and 
their  molecular  reactions  and  the  changes  which  they  undergo  in 
the  body  cannot  therefore  be  expressed  by  the  ordinary  chemical 
phrases  which  are  adapted  to  inorganic  substances.  Their  true 
characters,  as  proximate  principles,  are  accordingly  to  be  sought 
for  in  other  properties  than  those  which  depend  upon  their  exact 
ultimate  composition. 

One  of  these  characters  is  that  they  are  hygroscopic.  As  met  with 
in  different  parts  of  the  body,  they  present  different  degrees  of  con- 
sistency ;  some  being  nearly  solid,  others  more  or  less  fluid.  But  on 
being  subjected  to  evaporation  they  all  lose  water,  and  are  reduced 
to  a  perfectly  solid  form.  If  after  this  desiccation  they  be  exposed 
to  the  contact  of  moisture,  they  again  absorb  water,  swell,  and 
regain  their  original  mass  and  consistency.  This  phenomenon  is 
quite  different  from  that  of  capillary  attraction,  by  which  some  in- 
organic substances  become  moistened  when  exposed  to  the  contact 
of  water ;  for  in  the  latter  case  the  water  is  simply  entangled  me- 
chanically in  the  meshes  and  pores  of  the  inorganic  body,  while  that 
which  is  absorbed  by  the  organic  matter  is  actually  united  with  its 
substance,  and  diffused  equally  throughout  its  entire  mass.  Every 
organic  matter  is  naturally  united  in  this  way  with  a  certain  quantity 
of  water,  some  more  and  some  less.  Thus  the  albumen  of  the  blood 
is  in  union  with  so  much  water  that  it  has  the  fluid  form,  while  the 
organic  substance  of  cartilage  contains  less  and  is  of  a  firmer  con- 
sistency. The  quantity  of  water  contained  in  each  organic  sub- 
stance may  be  diminished  by  artificial  desiccation,  or  by  a  deficient 
supply ;  but  neither  of  them  can  be  made  to  take  up  more  than  a 
certain  amount.  Thus  if  the  albumen  of  the  blood  and  the  organic 
substance  of  cartilage  be  both  reduced  by  evaporation  to  a  similar 
degree  of  dryness  and  then  placed  in  water,  the  albumen  will  absorb 
so  much  as  again  to  become  fluid,  but  the  cartilaginous  substance 
only  so  much  as  to  regain  its  usual  nearly  solid  consistency.  Even 
where  the  organic  substance,  therefore,  as  in  the  case  of  albumen, 
becomes  fluid  under  these  circumstances,  it  is  not  exactly  a  solution 
of  it  in  water,  but  only  a  reabsorption  by  it  of  that  quantity  of  fluid 
with  which  it  is  naturally  associated. 
7 


98  PROXIMATE    PKIXCIPLES    OF    THE    THIRD    CLASS, 

Another  peculiar  phenomenon  characteristic  of  organic  substances 
is  their  coagulation.  Those  which  are  naturally  fluid  suddenly  as- 
sume, under  certain  conditions,  a  solid  or  semi-solid  consistency. 
They  are  then  said  to  be  coagulated ;  and  after  coagulation  they 
cannot  be  made  to  resume  their  original  condition.  Thus  fibrin 
coagulates  on  being  withdrawn  from  the  bloodvessels,  albumen  on 
being  subjected  to  the  temperature  of  boiling  water,  casein  on  being 
placed  in  contact  with  an  acid.  When  an  organic  substance  thus 
coagulates,  the  change  which  takes  place  is  a  peculiar  one,  and  has 
no  resemblance  to  the  precipitation  of  a  solid  substance  from  a 
watery  solution.  On  the  contrary,  the  organic  substance  merely 
assumes  a  special  condition ;  and  in  passing  into  the  solid  form  it 
retains  all  the  water  with  which  it  was  previously  united.  Albumen, 
for  example,  after  coagulation,  retains  the  same  quantity  of  water  in 
union  with  it,  which  it  held  before.  After  coagulation,  accordingly, 
this  water  may  be  driven  off  by  evaporation,  in  the  same  manner 
as  previously  ;  and  on  being  again  exposed  to  moisture,  the  organic 
matter  will  again  absorb  the  same  quantity,  though  it  will  not  re- 
sume the  fluid  form.  • 

By  coagulation,  an  organic  substance  is  permanently  altered ;  and 
though  it  may  be  afterwards  dissolved  by  certain  chemical  re-agents, 
as,  for  example,  the  caustic  alkalies,  it  is  not  thereby  restored  to  its 
original  condition,  but  only  suffers  a  still  further  alteration. 

In  many  instances  we  are  obliged  to  resort  to  coagulation  in 
order  to  separate  an  organic  substance  from  the  other  proximate 
principles  with  which  it  is  associated.  This  is  the  case,  for  example, 
with  the  fibrin  of  the  blood,  which  is  obtained  in  the  form  of  floc- 
culi,  by  beating  freshly-drawn  blood  with  a  bundle  of  rods.  But 
when  separated  in  this  way,  it  is  already  in  an  unnatural  condition, 
and  no  longer  represents  exactly  the  original  fluid  fibrin,  as  it  ex- 
isted in  the  circulating  blood.  Nevertheless,  this  is  the  only  mode 
in  which  it  can  be  examined,  as  there  are  no  means  of  bringing  it 
back  to  its  previous  condition. 

Another  important  property  of  the  organic  substances  is  that 
they  readily  excite,  in  other  proximate  principles  and  in  each  other, 
those  peculiar  indirect  chemical  changes  which  are  termed  catalyses 
or  catalytic  transformations.  That  is  to  say,  they  produce  the  changes 
referred  to,  not  directly,  by  combining  with  the  substance  which 
suffers  alteration,  or  with  any  of  its  ingredients ;  but  simply  by  their 
presence  which  induces  the  chemical  change  in  an  indirect  manner. 
Thus,  the  organic  substances  of  the  intestinal  fluids  induce  a  cata- 


ORGANIC    SUBSTANCES.  99 

lytic  action  by  which  starch,  is  converted  into  sugar.  The  albumen 
of  the  blood,  by  contact  with  the  organic  substance  of  the  muscular 
fibre,  is  transformed  into  a  substance  similar  to  it.  The  entire 
process  of  nutrition,  so  far  as  the  organic  matters  are  concerned, 
consists  of  such  catalytic  transformations.  Many  crystallizable 
substances,  which  when  pure  remain  unaltered  in  the  air,  become 
changed  if  mingled  with  organic  substances,  even  in  small  quantity. 
Thus  the  casein  of  milk,  after  being  exposed  for  a  short  time  to  a 
warm  atmosphere,  becomes  a  catalytic  body,  and  converts  the  sugar 
of  the  milk  into  lactic  acid.  In  this  change  there  is  no  loss  nor 
addition  of  any  chemical  element,  since  lactic  acid  has  precisely  the 
same  ultimate  composition  with  sugar  of  milk.  It  is  simply  a 
transformation  induced  by  the  presence  of  the  casein.  Oily  matters, 
which  are  entirely  unalterable  when  pure,  readily  become  rancid  at 
warm  temperatures,  if  mingled  with  an  organic  impurity. 

Fourthly,  The  organic  substances,  when  beginning  to  undergo 
decay,  induce  in  certain  other  substances  the  phenomena  of  fer- 
tnentation.  Thus,  the  mucus  of  the  urinary  bladder,  after  a  short 
exposure  to  the  atmosphere,  causes  the  urea  of  the  urine  to  be  con- 
verted into  carbonate  of  ammonia,  with  the  development  of  gaseous 
bubbles.  The  organic  matters  of  grape  juice,  under  similar  circum- 
stances, give  rise  to  fermentation  of  the  sugar,  by  which  it  is  con- 
verted into  alcohol  and  carbonic  acid. 

Fifthly,  The  organic  substances  are  the  only  ones  capable  of 
undergoing  the  process  of  'putrefaction.  This  process  is  a  compli- 
cated one,  and  is  characterized  by  a  gradual  liquefaction  of  the  ani- 
mal substance,  by  many  mutual  decompositions  of  the  saline  matters 
which  are  associated  with  it,  and  by  the  development  of  peculiarly 
fetid  and  unwholesome  gases,  among  which  are  carbonic  acid, 
nitrogen,  sulphuretted,  phosphoretted,  and  carburetted  hydrogen, 
and  ammoniacal  vapors.  Putrefaction  takes  place  constantly  after 
death,  if  the  organic  tissue  be  exposed  to  a  moist  atmosphere  at  a 
moderately  warm  temperature.  It  is  much  hastened  by  the  presence 
of  other  organic  substances,  in  which  decomposition  has  already 
commenced. 

The  organic  substances  are  readily  distinguished,  by  the  above 
general  characters,  from  all  other  kinds  of  proximate  principles. 
They  are  quite  numerous ;  nearly  every  animal  fluid  and  tissue 
containing  at  least  one  which  is  peculiar  to  itself.  They  have  not 
as  yet  been  all  accurately  described.  The  following  list,  however, 
comprises  the  most  important  of  them,  and  those  with  which  we  are 


100        PKOXIMATE    PEINCIPLES    OF    THE    THIED    CLASS. 

at  present  most  thorouglily  acquainted.     The  first  seven  are  fluid, 
or  nearly  so,  and  either  colorless  or  of  a  faint  yellowish  tinge. 

1.  FiBElisr. — Fibrin  is  found  in  the  blood ;  where  it  exists,  in  the 
human  subject,  in  the  proportion  of  two  to  three  parts  per  thousand. 
It  is  fluid,  and  mingled  intimately  with  the  other  ingredients  of  the 
blood.  It  occurs  also,  but  in  much  smaller  quantity,  in  the  lymph. 
It  is  distinguished  by  what  is  called  its  "  spontaneous"  coagulation ; 
that  is,  it  coagulates  on  being  withdrawn  from  the  vessels,  or  on  the 
occurrence  of  any  stoppage  to  the  circulation.  It  is  rather  more 
abundant  in  the  blood  of  some  of  the  lower  animals  than  in  that  of 
th  human  subject.  In  general,  it  is  found  in  larger  quantity  in 
the  blood  of  the  herbivora  than  in  that  of  the  carnivora. 

2.  Albumen". — Albumen  occurs  in  the  blood,  the  lymph,  the 
fluid  of  the  pericardium,  and  in  that  of  the  serous  cavities  gene- 
rally. It  is  also  present  in  the  fluid  which  may  be  extracted  by 
pressure  from  the  muscular  tissue.  In  the  blood  it  occurs  in  the 
proportion  of  about  seventy-five  parts  per  thousand.  The  white  of 
egg,  which  usually  goes  by  the  same  name,  is  not  identical  with  the 
albumen  of  the  blood,  though  it  resembles  it  in  some  respects ;  it  is 
properly  a  secretion  from  the  mucous  membrane  of  the  fowl's  ovi- 
duct, and  should  be  considered  as  a  distinct  organic  substance. 
Albumen  coagulates  on  being  raised  to  the  temperature  of  160°  F.; 
and  the  coagulum,  like  that  of  all  the  other  proximate  principles,  is 
soluble  in  caustic  potassa.  It  coagulates  also  by  contact  with  alco- 
hol, the  mineral  acids,  ferrocyanide  of  potassium  in  an  acidulated 
solution,  tannin,  and  the  metallic  salts.  The  alcoholic  coagulum,  if 
separated  from  the  alcohol  by  washing,  does  not  redissolve  in  water. 
A  very  small  quantity  of  albumen  has  been  sometimes  found  in  the 
saliva. 

8.  CASEiisf. — This  substance  exists  in  milk,  in  the  proportion  of 
about  forty  parts  per  thousand.  It  coagulates  by  contact  with  all 
the  acids,  mineral  and  organic ;  but  is  not  affected  by  a  boiling 
temperature.  It  is  coagulated  also  by  the  juices  of  the  stomach. 
It  is  important  as  an  article  of  food,  being  the  principal  organic 
ingredient  in  all  the  preparations  of  milk.  In  a  coagulated  form, 
it  constitutes  the  different  varieties  of  cheese,  which  are  more  or 
less  highly  flavored  with  various  oily  matters  remaining  entangled 
i.n  the  coao-ulated  casein. 


GLOBULINE. — MUCOSINE.  101 

What  is  called  vegetable  casein  or  "  legumine,"  is  different  from 
the  casein  of  milk,  and  constitutes  the  organic  substance  present  in 
various  kinds  of  peas  and  beans. 

4.  Globuline. — This  is  the  organic  substance  forming  the  prin- 
cipal mass  of  the  red  globules  of  the  blood.  It  is  nearly  fluid  in 
its  natural  -condition,  and  readily  dissolves  in  water.  It  does  not 
dissolve,  however,  in  the  serum  of  the  blood ;  and  the  globules, 
therefore,  retain  their  natural  form  and  consistency,  unless  the 
serum  be  diluted  with  an  excess  of  water.  Globuline  resembles 
albumen  in  coagulating  at  the  temperature  of  boiling  water.  It  is 
said  to  differ  from  it,  however,  in  not  being  coagulated  by  contact 
with  alcohol. 

5.  Pepsine. — This  substance  occurs  as  an  ingredient  in  the  gas- 
tric juice.  It  is  not  the  same  substance  which  Schwann  extracted 
by  maceration  from  the  mucous  membrane  of  the  stomach,  and 
which  is  regarded  by  Eobin,  Bernard,  &c.,  as  only  an  artificial  pro- 
duct of  the  alteration  of  the  gastric  tissues.  There  seems  no  good 
reason,  furthermore,  why  we  should  not  designate  by  this  name  the 
organic  substance  which  really  exists  in  the  gastric  juice.  Xt  occurs 
in  this  fluid  in  very  small  quantity,  not  over  fifteen  parts  per 
thousand.  It  is  coagulable  by  heat,  and  also  by  contact  with  alco- 
hol. But  if  the  alcoholic  coagulum  be  well  washed,  it  is  again 
soluble  in  a  watery  acidulated  fluid. 

6.  Pancreatine. — This  is  the  organic  substance  of  the  pancreatic 
juice,  where  it  occurs  in  great  abundance.  It  coagulates  by  heat, 
and  by  contact  with  sulphate  of  magnesia  in  excess.  In  its  natural 
condition  it  is  fluid,  but  has  a  considerable  degree  of  viscidity. 

7.  MuscosiNE  is  the  organic  substance  which  is  found  in  the  dif- 
ferent varieties  of  mucus,  and  which  imparts  to  them  their  viscidity 
and  other  physical  characters.  Some  of  these  mucous  secretions 
are  so  mixed  with  other  fluids,  that  their  consistency  is  more  or  less 
diminished ;  others,  which  remain  pure,  like  that  secreted  by  the 
mucous  follicles  of  the  cervix  uteri,  have  nearly  a  semi-solid  con- 
sistency. But  little  is  known  with  regard  to  their  other  specific 
characters. 

The  next  three  organic  substances  are  solid  or  semi-solid  in  con- 
sistency. 


102        PROXIMATE    PRINCIPLES    OF    THE    THIRD    CLASS. 

8.  OsTEiNE  is  the  organic  substance  of  tlie  bones,  in  wliicli  it  is 
associated  with  a  large  proportion  of  phosphate  of  lime.  It  exists, 
in  those  bones  which  have  been  examined,  in  the  proportion  of 
about  two  hundred  parts  per  thousand.  It  is  this  substance  which 
by  long  boiling  of  the  bones  is  transformed  into  gelatine  or  glue. 
In  its  natural  condition,  however,  it  is  insoluble  in  water,  even  at 
the  boiling  temperature,  and  becomes  soluble  only  after  it  has  been 
permanently  altered  by  ebullition. 

9.  Cartilagine. — This  forms  the  organic  ingredient  of  cartilage. 
Like  that  of  the  bones,  it  is  altered  by  long  boiling,  and  is  converted 
into  a  peculiar  kind  of  gelatine  termed  "chondrine."  Chondrine 
differs  from  the  gelatine  of  bones  principally  in  being  precipitated 
by  acids  and  certain  metallic  salts  which  have  no  effect  on  the  latter. 
Cartilagine,  in  its  natural  condition,  is  very  solid,  and  is  closely 
united  with  the  calcareous  salts. 

10.  MuscuLiNE. — This  substance  forms  the  principal  mass  of  the 
muscular  fibre.  It  is  semi-solid,  and  insoluble  in  water,  but  soluble 
in  dilute  muriatic  acid,  from  which  it  may  be  again  precipitated  by 
neutralizing  with  an  alkali.  It  closely  resembles  albumen  in  its 
chemical  composition,  and  like  it,  contains,  according  to  Scherer, 
two  equivalents  of  sulphur. 

The  four  remaining  organic  substances  form  a  somewhat  peculiar 
group.  They  are  the  coloring  matters  of  the  body.  They  exist 
always  in  small  quantity,  compared  with  the  other  ingredients,  but 
communicate  to  the  tissues  and  fluids  a  very  distinct  coloration. 
They  all  contain  iron  as  one  of  their  ultimate  elements. 

11.  H^matine  is  the  coloring  matter  of  the  red  globules  of  the 
blood.  It  is  nearly  fluid  like  the  globuline,  and  is  united  with  it 
in  a  kind  of  mutual  solution.  It  is  much  less  abundant  than  the 
globuline,  and  exists  in  the  proportion  of  about  one  part  of  hsema- 
tine  to  seventeen  parts  of  globuline.  The  following  is  the  formula 
for  its  composition  which  is  adopted  by  Lehmann : — 

Hsematine ^  C^^HjgNgOgFe. 

When  the  blood-globules  from  any  cause  become  disintegrated,  the 
haematine  is  readily  imbibed  after  death  by  the  walls  of  the  blood- 
vessels and  the  neighboring  parts,  staining  them  of  a  deep  red 
color,    "^his  coloration  has  sometimes  been  mistaken  for  an  evidence 


MELANINE. — UROSACINE.  103 

of  arteritis  ;  but  is  really  a  simple  effect  of  post-mortem  imbibition, 
as  above  stated. 

12.  Melanine. — Tbis  is  tbe  blackisb-brown  coloring  matter 
which  is  found  in  the  choroid  coat  of  the  eye,  the  iris,  the  hair,  and 
more  or  less  abundantly  in  the  epidermis.  So  far  as  can  be  ascer- 
tained, the  coloring  matter  is  the  same  in  all  these  situations.  It  is 
very  abundant  in  the  black  and  brown  races,  less  so  in  the  yellow 
and  white,  but  is  present  to  a  certain  extent  in  all.  Even  where 
the  tinges  produced  are  entirely  different,  as,  for  example,  in  brown 
and  blue  eyes,  the  coloring  matter  appears  to  be  the  same  in  cha- 
racter, and  to  vary  only  in  its  quantity  and  the  mode  of  its  arrange- 
ment; for  the  tinge  of  an  animal  tissue  does  not  depend  on  its 
local  pigment  only,  but  also  on  the  muscular  fibres,  fibres  of  areolar 
tissue,  capillary  bloodvessels,  &c.  All  these  ingredients  of  the 
tissue  are  partially  transparent,  and  by  their  mutual  interlacement" 
and  superposition  modify  more  or  less  the  effect  of  the  pigment 
which  is  deposited  below  or  among  them. 

Melanine  is  insoluble  in  water  and  the  dilute  acids,  but  dissolves 
slowly  in  caustic  potassa.  Its  ultimate  composition  resembles  that 
of  haematine,  but  the  proportion  of  iron  is  smaller. 

13.  BiLiVERDiNE  is  the  coloring  matter  of  the  bile.  It  is  yellow 
by  transmitted  light,  greenish  by  reflected  light.  On  exposure  to 
the  air  in  its  natural  fluid  condition,  it  absorbs  oxygen  and  assumes 
a  bright  grass-green  color.  The  same  effect  is  produced  by  treating 
it  with  nitric  acid  or  other  oxidizing  substances.  It  occurs  in  very 
small  quantity  in  the  bile,  from  which  it  may  be  extracted  by  pre- 
cipitating it  with  milk  of  lime  (Eobin),  from  which  it  is  afterward 
separated  by  dissolving  out  the  lime  with  muriatic  acid.  Obtained 
in  this  form,  however,  it  is  insoluble  in  water,  having  been  coagu- 
lated by  contact  with  the  calcareous  matter ;  and  is  not,  therefore, 
precisely  in  its  original  condition. 

14.  Urosacine  is  the  yellowish-red  coloring  matter  of  the  urine. 
It  consists  of  the  same  ultimate  elements  as  the  other  coloring  mat- 
ters, but  occurs  in  the  urine  in  such  minute  quantity,  that  the 
relative  proportion  of  its  elements  has  never  been  determined.  It 
readily  adheres  to  insoluble  matters  when  they  are  precipitated  from 
the  urine,  and  is  consequently  found  almost  always,  to  a  greater  or 
less  extent,  as  an  ingredient  in  urinary  calculi  formed  of  the  urates 


104        PROXIMATE    PRINCIPLES    OF    THE    THIRD    CLASS. 

or  of  uric  acid.  When  tlie  urates  are  thrown  down  also  in  the  form 
of  a  powder,  as  a  nrinarj  deposit,  they  are  usually  colored  more  or 
less  deeply,  according  to  the  quantity  of  urosacine  which  is  preci- 
pitated with  them. 

The  organic  substances  which  exist  in  the  body  require  for  their 
production  an  abundant  supply  of  similar  substances  in  the  food. 
All  highly  nutritious  articles  of  diet,  therefore,  contain  more  or  less 
of  these  substances.  Still,  though  nitrogenous  matters  must  be 
abundantl}^  supplied,  under  some  form,  from  without,  yet  the  par- 
ticular kinds  of  organic  substances,  characteristic  of  the  tissues,  are 
formed  in  the  body  by  a  transformation  of  those  which  are  intro- 
duced with  the  food.  The  organic  matters  derived  from  vegetables, 
though  similar  in  their  general  characters  to  those  existing  in  the 
animal  body,  are  yet  specifically  different.  The  gluten  of  wheat, 
the  legumine  of  peas  and  beans,  are  not  the  same  with  animal  albu- 
men and  fibrin.  The  only  organic  substances  taken  with  animal 
food,  as  a  general  rule,  are  the  albumen  of  eggs,  the  casein  of  milk, 
and  the  musculine  of  flesh ;  and  even  these,  in  the  food  of  the 
human  species,  are  so  altered  and  coagulated  by  the  process  of 
cooking,  as  to  lose  their  specific  characters  before  being  introduced 
into  the  alimentary  canal.  They  are  still  further  changed  by  the 
process  of  digestion,  and  are  absorbed  under  another  form  into  the 
blood.  But  from  their  subsequent  metamorphoses  there  are  formed, 
in  the  different  parts  of  the  body,  osteine,  cartilagine,  hsematine, 
globuline,  and  all  the  other  varieties  of  organic  matter  that  cha- 
racterize the  different  tissues.  These  varieties,  therefore,  originate 
as  such  in  the  animal  economy  by  the  catalytic  changes  which  the 
ingredients  of  the  blood  undergo  in  nutrition. 

Only  a  very  small  quantity  of  organic  matter  is  discharged 
with  the  excretions.  The  coloring  matters  of  the  bile  and  urine, 
and  the  mucus  of  the  urinary  bladder,  are  almost  the  only  ones 
that  find  an  exit  from  the  body  in  this  way.  There  is  a  minute 
quantity  of  organic  matter  exhaled  in  a  volatile  form  with  the 
breath,  and  a  little  also,  in  all  probability,  from  the  cutaneous  sur- 
face. But  the  entire  quantity  so  discharged  bears  but  a  very  small 
proportion  to  that  which  is  daily  introduced  with  the  food.  The 
organic  substances,  therefore,  are  decomposed  in  the  interior  of  the 
body.  They  are  transformed  by  the  process  of  destructive  assimi- 
lation, and  their  elements  are  finally  eliminated  and  discharged 
under  other  forms  of  combination. 


OF    FOOD.  105 


CHAPTER    V. 

OF  FOOD. 

Undee  the  term  "  food"  are  included  all  those  substances,  solid 
and  liquid,  whicli  are  necessary  to  sustain  the  process  of  nutrition. 
The  first  act  of  this  process  is  the,  absorption  from  without  of  all 
those  materials  which  enter  into  the  composition  of  the  living  frame, 
or  of  others  which  may  be  converted  into  them  in  the  interior  of 
the  body. 

The  proximate  principles  of  the  first  class,  or  the  "inorganic 
substances,"  require  to  be  supplied  in  sufficient  quantity  to  keep  up 
the  natural  proportion  in  which  they  exist  in  the  various  solids  and 
fluids.  As  we  have  found  it  to  be  characteristic  of  these  substances, 
except  in  a  few  instances,  that  they  suffer  no  alteration  in  the  in- 
terior of  the  body,  but,  on  the  contrary,  are  absorbed,  deposited  in 
its  tissue,  and  pass  out  of  it  afterward  unchanged,  nearly  every  one 
of  them  requires  to  be  present  under  its  own  proper  form,  and  in 
sufficient  quantity  in  the  food.  The  alkaline  carbonates,  which 
are  formed,  as  we  have  seen,  by  a  decomposition  of  the  malates, 
citrates  and  tartrates,  constitute  almost  the  only  exception  to  this 
rule. 

Since  water  enters  so  largely  into  the  composition  of  nearly  every 
part  of  the  body,  it  is  equally  important  as  an  ingredient  of  the 
food.  In  the  case  of  the  human  subject,  it  is  probably  the  most 
important  substance  to  be  supplied  with  constancy  and  regularity, 
and  the  system  suffers  more  rapidly  when  entirely  deprived  of 
fluids,  than  when  the  supply  of  solid  food  only  is  withdrawn.  A 
man  may  pass  eight  or  ten  hours,  for  example,  without  solid  food, 
and  suffer  little  or  no  inconvenience ;  but  if  deprived  of  water  for 
the  same  length  of  time,  he  becomes  rapidly  exhausted,  and  feels 
the  deficiency  in  a  very  marked  degree.  Magendie  found,  in  his 
experiments  on  dogs  subjected  to  inanition,'  that  if  the  animals 

'  Comptes  Rendus,  vol.  xiii.  p.  256. 


106  OF    FOOD. 

were  supplied  with  water  alone  they  lived  six,  eight,  and  even  ten 
days  longer  than  if  they  were  deprived  at  the  same  time  of 'both 
solid  and  liquid  food.  Chloride  of  sodium,  also,  is  usually  added 
to  the  food  in  considerable  quantity,  and  requires  to  be  supplied 
with  tolerable  regularity ;  but  the  remaining  inorganic  materials, 
such  as  calcareous  salts,  the  alkaline  phosphates,  &c.,  occur  natu- 
rally in  sufficient  quantity  in  most  of  the  articles  which  are  used  as 
food. 

The  proximate  principles  of  the  second  class,  so  far  as  they  con- 
stitute ingredients  of  the  food,  are  naturally  divided  into  two 
groups :  1st,  the  sugar,  and  2d,  the  oily  matters.  Since  starch  is 
always  converted  into  sugar  in  the  process  of  digestion,  it  may  be 
included,  as  an  alimentary  substance,  in  the  same  group  with  the 
sugars.  There  is  a  natural  desire  in  the  human  species  for  both 
saccharine  and  oleaginous  food.  In  the  purely  carnivorous  animals, 
however,  though  no  starch  or  sugar  be  taken,  yet  the  body  is  main- 
tained in  a  healthy  condition.  It  has  been  supposed,  therefore,  th.at 
saccharine  matters  could  not  be  absolutely  necessary  as  food ;  the 
more  so  since  it  has  been  found,  by  the  experiments  of  CI,  Bernard, 
that,  in  carnivorous  animals  kept  exclusively  on  a  diet  of  flesh, 
sugar  is  still  formed  in  the  liver,  as  well  as  in  the  mammary  gland. 
The  above  conclusion,  however,  which  has  been  drawn  from  these 
facts,  does  not  apply  practically  to  the  human  species.  The  car- 
nivorous animals  have  no  desire  for  vegetable  food,  while  in  the 
human  species  there  is  a  natural  craving  for  it,  which  is  almost 
universal.  It  may  be  dispensed  with  for  a  few  days,  but  not  with 
impunity  for  any  great  length  of  time.  The  experiment  has  often 
enough  been  tried,  in  the  treatment  of  diabetes,  of  confining  the 
patient  to  a  strictly  animal  diet.  It  has  been  invariably  found  that, 
if  this  regimen  be  continued  for  some  weeks,  the  desire  for  vegetable 
food  on  the  part  of  the  patient  becomes  so  imperative  that  the  plan 
of  treatment  is  unavoidably  abandoned. 

A  similar  question  has  also  arisen  with  regard  to  the  oleaginous 
matters.  Are  these  substances  mdispensable  as  ingredients  of  the 
food,  or  may  they  be  replaced  by  other  proximate  principles,  such 
as  starch  or  sugar  ?  It  has  already  been  seen,  from  the  experiments 
of  Boussingault  and  others,  that  a  certain  amount  of  fat  is  produced 
in  the  body  over,  and  above  that  which  is  taken  with  the  food ;  and 
it  appears  also  that  a  regimen  abounding  in  saccharine  substances 
is  favorable  to  the  production  of  fat.  It  is  altogether  probable, 
therefore,  that  the  materials  for   the   production  of  fat   may  be 


OF    FOOD.  107 

derived,  under  these  circumstances,  either  directly  or  indirectly 
from  saccharine  matters.  But  saccharine  matters  alone  are  not 
entirely  sufficient.  M.  Huber'  thought  he  had  demonstrated  that 
bees  fed  on  pure  sugar  would  produce  enough  wax  to  show  that 
the  sugar  could  supply  all  that  was  necessary  to  the  formation  of 
the  fatty  matter  of  the  wax.  Dumas  and  Milne-Edwards,  however, 
in  repeating  Huber's  experiments,^  found  that  this  was  not  the  case. 
Bees,  fed  on  pure  sugar,  soon  cease  to  work,  and  sometimes  perish 
in  considerable  numbers;  but  if  fed  with  honey,  which  contains 
some  waxy  and  other  matters  beside  the  sugar,  they  thrive  upon 
it ;  and  produce,  in  a  given  time,  a  much  larger  quantity  of  fat 
than  was  contained  in  the  whole  supply  of  food. 

The  same  thing  was  established  by  Boussingault  with  regard  to 
starchy  matters.  He  found  that  in  fattening  pigs,  though  the 
quantity  of  fat  accumulated  by  the  animal  considerably  exceeded 
that  contained  in  the  food,  yet  fat  must  enter  to  some  extent  into 
the  composition  of  the  food  in  order  to  maintain  the  animals  in  a 
good  condition ;  for  pigs,  fed  on  boiled  potatoes  alone  (an  article 
abounding  in  starch  but  nearly  destitute  of  oily  matter),  fattened 
slowly  and  with  great  difficulty ;  while  those  fed  on  potatoes  mixed 
with  a  greasy  fluid  fattened  readily,  and  accumulated,  as  mentioned 
above,  much  more  fat  than  was  contained  in  the  food. 

The  apparent  discrepancy  between  these  facts  may  be  easily  ex- 
plained, when  we  recollect  that,  in  order  that  the  animal  may  become 
fattened,  it  is  necessary  that  he  be  supplied  not  only  with  the 
materials  of  the  fat  itself,  but  also  with  everything  else  which  is 
necessary  to  maintain  the  body  in  a  healthy  condition.  Oleaginous 
matter  is  one  of  these  necessary  substances.  The  fats  which  are 
taken  in  with  the  food  are  not  destined  to  be  simply  transported 
into  the  body  and  deposited  there  unchanged.  On  the  contrary, 
they  are  altered  and  used  up  in  the  processes  of  digestion  and 
nutrition ;  while  the  fats  which  appear  in  the  body  as  constituents 
of  the  tissues  are,  in  great  part,  of  new  formation,  and  are  produced 
from  materials  derived,  perhaps,  from  a  variety  of  different  sources. 

It  is  certain,  then,  that  either  one  or  the  other  of  these  two 
groups  of  substances,  saccharine  or  oleaginous,  must  enter  into  the 
composition  of  the  food ;  and  furthermore,  that,  though  the  oily 
matters  may  sometimes  be  produced  in  the  body  from  the  sugars, 

'  Natural  History  of  Bees,  Edinburgh,  1821,  p.  330. 

*  Annales  de  Cliiui.  et  do  Plivrf.,  3d  series,  vol.  xiv.  p.  400. 


108  OF    FOOD. 

it  is  also  necessary  for  tlie  perfect  nutrition  of  the  body  that  fat  be 
supplied,  under  its  own  form,  with  the  food.  For  the  human 
species,  also,  it  is  natural  to  have  them  both  associated  in  the 
alimentary  materials.  They  occur  together  in  most  vegetable  sub- 
stances, and  there  is  a  natural  desire  for  them  both,  as  elements  of 
the  food. 

They  are  not,  however,  when  alone,  or  even  associated  with  each 
other,  sufficient  for  the  nutrition  of  the  animal  body.  Magendie 
found  that  dogs,  fed  exclusively  on  starch  or  sugar,  perished  after  a 
short  time  with  symptoms  of  profound  disturbance  of  the  nutritive 
functions.  An  exclusive  diet  of  butter  or  lard  had  a  similar  effect. 
The  animal  became  exceedingly  debilitated,  though  without  much 
emaciation;  and  after  death,  all  the  internal  organs  and  tissues 
were  found  infiltrated  with  oil.  Boussingault'  performed  a  similar 
experiment,  with  a  like  result,  upon  a  duck,  which  was  kept  upon 
an  exclusive  regimen  of  butter.  "  The  duck  received  1350  to  1500 
grains  of  butter  every  day.  At  the  end  of  three  weeks  it  died  of 
inanition.  The  butter  oozed  from  every  part  of  its  body.  The 
feathers  looked  as  though  they  had  been  steeped  in  melted  butter, 
and  the  body  exhaled  an  unwholesome  odor  like  that  of  butyric 
acid." 

Lehmann  was  also  led  to  the  same  result  by  some  experiments 
which  he  performed  upon  himself  for  the  purpose  of  ascertaining 
the  effect  produced  on  the  urine  by  different  kinds  of  food.^ 
This  observer  confined  himself  first  to  a  purely  animal  diet  for 
three  weeks,  and  afterwards  to  a  purely  vegetable  one  for  sixteen 
days,  without  suffering  any  marked  inconvenience.  .  He  then  put 
himself  upon  a  regimen  consisting  entirely  of  non-nitrogenous  sub- 
stances, starch,  sugar,  gum,  and  oil,  but  was  only  able  to  continue 
this  diet  for  two,  or  at  most  for  three  days,  owing  to  the  marked 
disturbance  of  the  general  health  which  rapidly  supervened.  The 
unpleasant  symptoms,  however,  immediately  disappeared  on  his 
return  to  an  ordinary  mixed  diet.  The  same  fact  has  been  esta- 
blished more  recently  by  Prof.  Wm.  A.  Hammond,^  in  a  series  of 
experiments  which  he  performed  upon  himself.  He  was  enabled 
to  live  for  ten  days  on  a  diet  composed  exclusively  of  boiled  starch 
and  water.    After  the  third  day,  however,  the  general  health  began 

'  CWmie  Agricole,  p.  166. 

^  Journal  fur  praktische  Chetnie,  vol.  xxvii.  p.  257. 

*  Experimental  Eesearclies,  &c.,  being  the  Prize  Essay  of  the  American  Medical 
Association  for  1857. 


OF    FOOD.  109 

to  deteriorate,  and  became  very  mucli  disturbed  before  tbe  termi- 
nation of  the  experiment.  The  prominent  symptoms  were  debility, 
headache,  pyrosis,  and  palpitation  of  the  heart.  After  the  starchy 
diet  was  abandoned,  it  required  some  days  to  restore  the  health  to 
its  usual  condition. 

The  proximate  principles  of  the  third  class,  or  the  organic  sub- 
stances proper,  enter  so  largely  into  the  constitution  of  the  animal 
tissues  and  fluids,  that  their  importance,  as  elements  of  the  food,  is 
easily  understood.  No  food  can  be  long  nutritious,  unless  a  certain 
proportion  of  these  substances  be  present  in  it.  Since  they  are  so 
abundant  as  ingredients  of  the  body,  their  loss  or  absence  from  the 
food  is  felt  more  speedily  and  promptly  than  that  of  any  other  sub- 
stance except  water.  They  have,  therefore,  sometimes  received  the 
name  of  "nutritious  substances,"  in  contradistinction  to  those  of 
the  second  class,  which  contain  no  nitrogen,  and  which  have  been 
found  by  the  experiments  of  Magendie  and  others  to  be  insuf&cient 
for  the  support  of  life.  The  organic  substances,  however,  when 
taken  alone,  are  no  more  capable  of  supporting  life  indefinitely  than 
the  others.  It  was  found  in  the  experiments  of  the  French  "  Gela- 
tine Commission'"  that  animals  fed  on  pure  fibrin  and  albumen,  as 
well  as  those  fed  on  gelatine,  become,  after  a  short  time,  much  en- 
feebled, refuse  the  food  which  is  offered  to  them,  or  take  it  with 
reluctance,  and  finally  die  of  inanition.  This  result  has  been 
explained  by  supposing  that  these  substances,  when  taken  alone, 
excite  after  a  time  such,  disgust  in  the  animal  that  they  are  either 
no  longer  taken,  or  if  taken  are  not  digested.  But  this  disgust 
itself  is  simply  an  indication  that  the  substances  used  are  insufficient 
and  finally  useless  as  articles  of  food,  and  that  the  system  demands 
instinctively  other  materials  for  its  nourishment. 

The  instinctive  desire  of  animals  for  certain  substances  is  the 
surest  indication  that  they  are  in  reality  required  for  the  nutritive 
process;  and  on  the  other  hand,  the  indifference  or  repugnance 
manifested  for  injurious  or  useless  substances,  is  an  equal  evidence 
of  their  unfitness  as  articles  of  food.  This  repugnance  is  well  de- 
scribed by  Magendie,  in  the  report  of  the  commission  above  alluded 
to,  while  detailing  the  result  of  his  investigations  on  the  nutritive 
qualities  of  gelatine.  "  The  result,"  he  says,  "  of  these  first  trials 
was  that  pure  gelatine  was  not  to  the  taste  of  the  dogs  experimented 
on.     Some  of  them  suffered  the  pangs  of  hunger  with  the  gelatine 

'  Comptes  Rendus,  1841,  vol.  xiii.  p.  2-7. 


110  OF    FOOD. 

within  their  reach,  and  would  not  touch  it ;  others  tasted  of  it,  but 
would  not  eat ;  others  still  devoured  a  certain  quantity  of  it  once 
or  twice,  and  then  obstinately  refused  to  make  any  further  use  of  it," 

In  one  instance,  however,  Magendie  succeeded  in  inducing  a  dog 
to  take  a  considerable  quantity  of  pure  fibrin  daily  throughout  the 
whole  course  of  the  experiment;  but  notwithstanding  this,  the 
animal  became  emaciated  like  the  others,  and  died  at  last  with  the 
same  symptoms  of  inanition. 

The  alimentary  substances  of  the  second  class,  however,  viz.,  the 
sugars  and  the  oils,  have  been  sometimes  thought  less  important 
than  the  albuminous  matters,  because  they  do  not  enter  so  largely 
or  so  permanently  into  the  composition  of  the  solid  tissues.  The 
saccharine  matters,  when  taken  as  food,  cannot  be  traced  farther 
than  the  blood.  They  undergo  already,  in  the  circulating  fluid, 
some  change  by  which  their  essential  character  is  lost,  and  they 
cannot  be  any  longer  recognized.  The  appearance  of  sugar  in  the 
mammary  gland  and  the  milk  is  only  exceptional,  and  does  not 
occur  at  all  in  the  male  subject.  The  fats  are,  it  is  true,  very  gene- 
rally distributed  throughout  the  body,  but  it  is  only  in  the  brain 
and  nervous  matter  that  they  exist  intimately  united  with  the  re- 
maining ingredients  of  the  tissues.  Elsewhere,  as  already  mentioned, 
they  are  deposited  in  distinct  drops  and  granules,  and  so  long  as 
they  remain  in  this  condition  must  of  course  be  inactive,  so  far  as 
regards  any  chemical  nutritive  process.  In  this  condition  they 
seem  to  be  held  in  reserve,  ready  to  be  absorbed  by  the  blood, 
whenever  they  may  be  required  for  the  purposes  of  nutrition.  On 
being  reabsorbed,  however,  as  soon  as  they  again  enter  the  blood 
or  unite  intimately  with  the  substance  of  the  tissues,  they  at  once 
change  their  condition  and  lose  their  former  chemical  constitution 
and  properties. 

It  is  for  these  reasons  that  the  albuminoid  matters  have  been 
sometimes  considered  as  the  only  "  nutritious"  substances,  because 
they  alone  constitute  under  their  own  form  a  great  part  of  the 
ingredients  of  the  tissues,  while  the  sugars  and  the  oils  rapidly  dis- 
appear by  decomposition.  It  has  even  been  assumed  that  the  pro- 
cess by  which  the  sugar  and  the  oils  disappear  is  one  of  direct 
combustion  or  oxidation,  and  that  they  are  destined  solely  to  be 
consumed  in  this  way,  not  to  enter  at  all  into  the  composition  of 
the  tissues  but  only  to  maintain  the  heat  of  the  body  by  an  inces- 
sant process  of  combustion  in  the  blood.  They  have  been  therefore 
termed  the  "  combustible"  or  "  heat-producing"  elements,  while  the 


OF    FOOD.  Ill 

albuminoid  substances  were  known  as  the  nutritious  or  "plastic" 
elements. 

This  distinction,  however,  has  no  real  foundation.  In  the  first 
place,  it  is  not  at  all  certain  that  the  sugars  and  the  oils  which  dis- 
appear in  the  body  are  destroyed  by  combustion.  This  is  merely 
an  inference  which  has  been  made  without  any  direct  proof.  All 
we  know  positively  in  regard  to  the  matter  is  that  these  substances 
soon  become  so  altered  in  the  blood  that  they  can  no  longer  be 
recognized  by  their  ordinary  chemical  properties  ;  but  we  are  still 
ignorant  of  the  exact  nature  of  the  transformations  which  they 
undergo.  Furthermore,  the  difference  between  the  sugars  and  the 
oils  on  the  one  hand,  and  the  albuminoid  substances  on  the  other, 
so  far  as  regards  their  decomposition  and  disappearance  in  the 
body,  is  only  a  difference  in  time.  The  albuminoid  substances 
become  transformed  more  slowly,  the  sugars  and  the  oils  more 
rapidly.  Even  if  it  should  be  ascertained  hereafter  that  the  sugars 
and  the  oils  really  do  not  unite  at  all  with  the  solid  tissues,  but  are 
entirely  decomposed  in  the  blood,  this  would  not  make  them  any 
less  important  as  alimentary  substances,  since  the  blood  is  as 
essential  a  part  of  the  body  as  the  solid  tissues,  and  its  nutrition 
must  be  provided  for  equally  with  theirs. 

It  is  evident,  therefore,  that  no  single  proximate  principle,  nor 
even  any  one  class  of  them  alone,  can  be  sufficient  for  the  nutrition 
of  the  body;  but  that  the  food,  to  be  nourishing,  must  contain 
substances  belonging  to  all  the  different  groups  of  proximate  prin- 
ciples. The  albuminoid  substances  are  first  in  importance  because 
they  constitute  the  largest  part  of  the  entire  mass  of  the  body ;  and 
exhaustion  therefore  follows  more  rapidly  when  they  are  withheld 
than  when  the  animal  is  deprived  of  other  kinds  of  alimentary 
matter.  But  starchy  and  oleaginous  substances  are  also  requisite  ; 
and  the  body  feels  the  want  of  them  sooner  or  later,  though  it  may 
be  plentifully  supplied  with  albumen  and  fibrin.  Finally,  the  in- 
organic saline  matters,  though  in  smaller  quantity,  are  also  neces- 
sary to  the  continuous  maintenance  of  life.  In  order  that  the 
animal  tissues  and  fluids  remain  in  a  healthy  condition  and  take 
their  proper  part  in  the  functions  of  life,  they  must  be  supplied 
with  all  the  ingredients  necessary  to  their  constitution ;  and  a  man 
may  be  starved  to  death  at  last  by  depriving  him  of  chloride  of 
sodium  or  phosphate  of  lime  just  as  surely,  though  not  so  rapidly, 
as  if  he  were  deprived  of  albumen  or  oil. 

In  the  different  kinds  of  food,  accordingly,  which  have  been 


112  OF    FOOD. 

adopted  by  tlie  ■aniversal  and  instinctive  choice  of  man,  the  three 
difl'erent  classes  of  proximate  principles  are  all  more  or  less  abund- 
antly represented.  In  all  of  them  there  exists  naturally  a  certain 
proportion  of  saline  substances ;  and  water  and  chloride  of  sodium 
are  generally  taken  with  them  in  addition.  In  milk,  the  first  food 
supplied  to  the  infant,  we  have  casein  which  is  an  albuminoid  sub- 
stance, butter  which  represents  the  oily  matters,  and  sugar  of  milk 
belonging  to  the  saccharine  group,  together  with  water  and  saline 
matters,  in  the  following  proportions  : — ^ 

Composition  of  Cow's  Milk. 

Water 87.02 

Casein 4.48 

Butter 3.13 

Sugar  of  milk 4.77 

Soda 

Chlorides  of  potassium  and  sodium       .... 

Phosphates  of  soda  and  potassa 

Phosphate  of  lime }•  0.60 

"  magnesia 

Alkaline  carbonates      ....... 

Iron,  &c 


100.00 


In  wheat  flour,  gluten  is  the  albuminoid  matter,  sugar  and  starch 
the  non-nitrogenous  principles. 


Composition  of  Wheat  Flouk. 

Gluten     . 

.     10.2                Gum 

.       2.8 

Starch     . 

.     72.8                Water      . 
.      4.2 

.     10.0 

Sugar 

100.0 

The  other  cereal  grains  mostly  contain  oil  in  addition  to  the 
above. 

Composition  of  Deied  Oatmeal. 

Starch 59.00 

Bitter  matter  and  sugar 8.25 

Gray  albuminous  matter       . 4.30 

Fatty  oil 2.00 

Gum 2.50 

Husk,  mixture,  and  loss 23.95 

100.00 
Eggs  contain  albumen  and  salts  in  the  white,  with  the  addition 
of  oily  matter  in  the  yolk. 

'  The  accompanying  analyses  of  various  kinds  of  food  are  taken  from  Pereira 
on  Food  and  Diet,  New  York,  1843. 


OF    FOOD.  113 

Composition  of  Eggs. 
White  of  Egg.  Yolk  of  Egg. 

Water  ....       80.00 53.78 

Albumen  and  mucus    •       15.28  ......       12.75 

Yellow  oil      ... 28.75 

Salts     ....        4.72 4.72 

100.00  100.00 

In  ordinary  flesh  or  butcher's  meat,  we  have  the  albumiaoid 
matter  of  the  muscular  fibre  and  the  fat  of  the  adipose  tissue. 

Composition  of  Okdinary  Botcher's  Meat. 

J  Water       ....     63.418 
Meat  devoid  of  fat        .        85.7         ic  ,.q       ..  oo  ooo 

t  Solid  matter      .         .         .     22.282 

Fat,  cellular  tissue,  &c 14.300 

100.000 

From  what  has  been  said  above,  it  will  easily  be  seen  that  the 
nutritious  character  of  any  substance,  or  its  value  as  an  article  of 
food,  does  not  depend  simply  upon  its  containing  either  one  of  the 
alimentary  substances  mentioned  above  in  large  quantity;  but  upon 
its  containing  them  mingled  together  in  such  proportion  as  is 
requisite  for  the  healthy  nutrition  of  the  body.  "What  these  pro- 
portions are  cannot  be  determined  from  simple  chemical  analysis, 
nor  from  any  other  data  than  those  derived  from  direct  observation 
and  experiment. 

The  total  quantity  of  food  required  by  man  has  been  variously 
estimated.  It  will  necessarily  vary,  indeed,  not  only  with  the  con- 
stitution and  habits  of  the  individual,  but  also  with  the  quality  of 
the  food  employed ;  since  some  articles,  such  as  corn  and  meat,  con- 
tain very  much  more  alimentary  material  in  the  same  bulk  than 
fresh  fruits  or  vegetables.  Any  estimate,  therefore,  of  the  total 
quantity  should  state  also  the  kind  of  food  used ;  otherwise  it  will 
be  altogether  without  value.  From  experiments  performed  while 
living  on  an  exclusive  diet  of  bread,  fresh  meat,  and  butter,  with 
cofl'ee  and  water  for  drink,  we  have  found  that  the  entire  quantity 
of  food  required  during  twenty-four  hours  by  a  man  in  full  health, 
and  taking  free  exercise  in  the  open  air,  is  as  follows : — 

Meat 16  ounces  or  1.00  lb.  Avoirdupois. 

Bread 19        "        "    1.19  "  " 

Batter  or  fat  .         .         .         .  3}       "       "   0.22  "  " 

Water 52  fluid  oz."   3.38  "  " 

That  is  to  say,  rather  less  than  two  and  a  half  pounds  of  solid  food, 
and  rather  over  three  pints  of  liquid  food. 
8 


114  OF    FOOD. 

Another  necessary  consideration,  in  estimating  the  value  of  any 
substance  as  an  article  of  food,  is  its  digestibility.  A  vegetable  or 
animal  tissue  may  contain  an  abundance  of  albuminoid  or  starchy 
matter,  but  may  be  at  the  same  time  of  such  an  unyielding  consist- 
ency as  to  be  insoluble  in  the  digestive  fluids,  and  therefore  useless 
as  an  article  of  food.  Bones  and  cartilages,  and  the  fibres  of  yellow 
elastic  tissue,  are  indigestible,  and  therefore  not  nutritious.  The 
same  remark  may  be  made  with  regard  to  the  substances  contained 
in  woody  fibre,  and  the  hard  coverings  and  kernels  of  various  fruits. 
Everything,  accordingly,  which  softens  or  disintegrates  a  hard  ali- 
mentary substance  renders  it  more  digestible,  and  so  far  increases 
its  value  as  .an  article  of  food. 

The  preparation  of  food  by  cooking  has  a  twofold  object :  first, 
to  soften  or  disintegrate  it,  and  second,  to  give  it  an  attractive 
flavor.  Many  vegetable  substances  are  so  hard  as  to  be  entirely 
indigestible  in  a  raw  state.  Eipe  peas  and  beans,  the  different  kinds 
of  grain,  and  many  roots  and  fruits,  require  to  be  softened  by  boil- 
ing, or  some  other  culinary  process,  before  they  are  ready  for  use. 
With  them,  the  principal  change  produced  by  cooking  is  an  altera- 
tion in  consistency.  With  most  kinds  of  animal  food,  however,  the 
effect  is  somewhat  different.  In  the  case  of  muscular  flesh,  for  ex- 
ample, the  muscular  fibres  themselves  are  almost  always  more  or 
less  hardened  by  boiling  or  roasting;  but,  at  the  same  time,  the 
fibrous  tissue  by  which  they  are  held  together  is  gelatinized  and 
softened,  so  that  the  muscular  fibres  are  more  easily  separated  from 
each  other,  and  more  readily  attacked  by  the  digestive  fluids.  But 
beside  this,  the  organic  substances  contained  in  meat,  which  are  all 
of  them  very  insipid  in  the  raw  state,  acquire  by  the  action  of  heat 
in  cooking,  a  peculiar  and  agreeable  flavor.  This  flavor  excites 
the  appetite  and  stimulates  the  flow  of  the  digestive  fluids,  and 
renders,  in  this  way,  the  entire  process  of  digestion  more  easy  and 
expeditious. 

The  changes  which  the  food  undergoes  in  the  interior  of  the  body 
may  be  included  under  three  different  heads :  first,  digestion,  or  the 
preparation  of  the  food  in  the  alimentary  canal ;  second,  assimilation, 
by  which  the  elements  of  the  food  are  converted  into  the  animal 
tissues ;  and  third,  excretion,  by  which  they  are  again  decomposed, 
and  finally  discharged  from  the  body. 


DIGESTION.  115 


CHAPTEE    VI. 

DIGESTION. 

Digestion"  is  that  process  by  which  the  food  is  reduced  to  a  form 
in  which  it  can  be  absorbed  from  the  intestinal  canal,  and  taken  up 
by  the  bloodvessels.  This  process  does  not  occur  in  vegetables. 
For  vegetables  are  dependent  for  their  nutrition,  mostly,  if  not 
entirely,  upon  a  supply  of  inorganic  substances,  as  water,  saline 
matters,  carbonic  acid,  and  ammonia.  These  materials  constitute 
the  food  upon  which  plants  subsist,  and  are  converted  in  their  inte- 
rior into  other  substances,  by  the  nutritive  process.  These  mate- 
rials, furthermore,  are  constantly  supplied  to  the  vegetable  under 
such  a  form  as  to  be  readily  absorbed.  Carbonic  acid  and  ammonia 
exist  in  a  gaseous  form  in  the  atmosphere.,  and  are  also  to  be  found 
in  solution,  together  with  the  requisite  saline  matters,  in  the  water 
with  which  the  soil  is  penetrated.  All  these  substances,  therefore, 
are  at  once  ready  for  absorption,  and  do  not  require  any  preliminary 
modification.  But  with  animals  and  man  the  case  is  different. 
They  cannot  subsist  upon  these  inorganic  substances  alone,  but 
require  for  their  support  materials  which  have  already  been  organ- 
ized, and  which  have  previously  constituted  a  part  of  animal  or 
vegetable  bodies.  Their  food  is  almost  invariably  solid  or  semi-solid 
at  the  time  when  it  is  taken,  and  insoluble  in  water.  Meat,  bread, 
fruits,  vegetables,  kc,  are  all  taken  into  the  stomach  in  a  solid  and 
insoluble  condition  ;  and  even  those  substances  which  are  naturally 
fluid,  such  as  milk,  albumen,  white  of  egg,  are  almost  always,  in 
the  human  species,  coagulated  and  solidified  by  the  process  of  cook- 
ing, before  being  taken  into  the  stomach. 

In  animals,  accordingly,  the  food  requires  to  undergo  a  process 
of  digestion,  or  liquefaction,  before  it  can  be  absorbed.  In  all  cases, 
the  general  characters  of  this  process  are  the  same.  It  consists 
essentially  in  the  food  being  received  into  a  canal,  running  through 
the  body  from  mouth  to  anus,  called  the  "alimentary  canal,"  in 
which  it  comes  in  contact  with  certain  digestive  fluids,  which  act 


116  DIGESTION". 

upon  it  in  such  a  way  as  to  liquefy  and  dissolve  it.  These  fluids 
are  secreted  by  the  mucous  membrane  of  the  alimentary  canal,  and 
by  certain  glandular  organs  situated  in  its  neighborhood.  Since  the 
food  always  consists,  as  we  have  already  seen,  of  a  mixture  of  vari- 
ous substances,  having  different  physical  and  chemical  properties, 
the  several  digestive  fluids  are  also  different  from  each  other ;  each 
one  of  them  exerting  a  peculiar  action,  which  is  more  or  less  con- 
fined to  particular  species  of  food.  As  the  food  passes  through  the 
intestine  from  above  downward,  those  parts  of  it  which  become 
liquefied  are  successively  removed  by  absorption,  and  taken  up  by 
the  vessels ;  while  the  remaining  portions,  consisting  of  the  indi- 
gestible matter,  together  with  the  refuse  of  the  intestinal  secretions, 
gradually  acquire  a  firmer  consistency  owing  to  the  absorption  of 
the  fluids,  and  are  finally  discharged  from  the  intestine  under  the 
form  of  feces. 

In  different  species  of  animals,  however,  the  difference  in  their 
habits,  in  the  constitution  of  their  tissues,  and  in  the  character  of 
their  food,  is  accompanied  with  a  corresponding  variation  in  the 
anatomy  of  the  digestive  apparatus,  and  the  character  of  the  secreted 
fluids.  As  a  general  rule,  the  digestive  apparatus  of  herbivorous 
animals  is  more  complex  than  that  of  the  carnivora  ;  since,  in  vege- 
table substances,  the  nutritious  matters  are  often  present  in  a  very 
solid  and  unmanageable  form,  as,  for  example,  in  raw  starch  and 
the  cereal  grains,  and  are  nearly  always  entangled  among  vegetable 
cells  and  fibres  of  an  indigestible  character.  In  those  instances 
where  the  food  consists  mostly  of  herbage,  as  grass,  leaves,  &c.,  the 
digestible  matters  bear  only  a  small  proportion  to  the  entire  quan- 
tity ;  and  a  large  mass  of  food  must  therefore  be  taken,  in  order 
that  the  requisite  amount  of  nutritious  material  may  be  extracted 
from  it.  In  such  cases,  accordingly,  the  alimentary  canal  is  large 
and  long;  and  is  divided  into  many  compartments,  in  which 
different  processes  of  disintegration,  transformation,  and  solution 
are  carried  on. 

In  the  common  fowl,  for  instance  (Fig.  16),  the  food,  which  con- 
sists mostly  of  grains,  and  frequently  of  insects  with  hard,  coria- 
ceous integument,  first  passes  down  the  oesophagus  (a)  into  a 
diverticulum  or  pouch  (b)  termed  the  crop.  Here  it  remains  for 
a  time  mingled  with  a  watery  secretion  in  which  the  grains  are 
macerated  and  softened.  The  food  is  then  carried  farther  down 
until  it  reaches  a  second  dilatation  (c),  the  proventriculus,  or 
secreting  stomach.     The   mucous   membrane    here  is   thick   and 


DIGESTION. 


117 


U 


^ 


glandular,  and  is  provided  with  numerous  se-  ^'g-  i^- 

creting  follicles  or  crypts.  From  them  an 
acid  fluid  is  poured  out,  by  which  the  food  is 
subjected  to  further  changes.  It  next  passes 
into  the  gizzard  {d),  or  triturating  stomach,  a 
cavity  inclosed  by  thick  muscular  walls,  and 
lined  with  a  remarkably  tough  and  horny 
epithelium.  Here  it  is  subjected  to  the  crush- 
ing and  grinding  action  of  the  muscular  pa- 
rietes,  assisted  by  grains  of  sand  and  gravel, 
which  the  animal  instinctively  swallows  with 
the  food,  by  which  it  is  so  triturated  and  dis- 
integrated, that  it  is  reduced  to  a  uniform  pulp, 
upon  which  the  digestive  fluids  can  effectually 
operate.  The  mass  then  passes  into  the  intes- 
tine (e),  where  it  meets  with  the  intestinal 
juices,  which  complete  the  process  of  solution ; 
and  from  the  intestinal  cavity  it  is  finally  ab- 
sorbed in  a  liquid  form,  by  the  vessels  of  the 
mucous  membrane. 

In  the  ox,  again,  the  sheep,  the  camel,  the 
deer,  and  all  ruminating  animals,  there  are 
four  distinct  stomachs  through  which  the 
food  passes  in  succession;  each  lined  with 
mucous  membrane  of  a  different  structure, 
and  adapted  to  perform  a  different  part  in 
the  digestive  process.  (Fig.  17.)  When  first 
swallowed,  the  food  is  received  into  the  ru- 
men, or  paunch  {b),  a  large  sac,  itself  par- 
tially divided  by  incomplete  partitions,  and 
lined  by  a  mucous  membrane  thickly  set 
with  long  prominences  or  villi.  Here  it  ac- 
cumulates while  the  animal  is  feeding,  and  is 
retained  and  macerated  in  its  own  fluids.  "When  the  animal  has 
finished  browsing,  and  the  process  of  rumination  commences,  the 
food  is  regurgitated  into  the  mouth  by  an  inverted  action  of  the 
muscular  walls  of  the  paunch  and  oesophagus,  and  slowly  masticated. 
It  then  descends  again  along  the  oesophagus ;  but  instead  of  enter- 
ing the  first  stomach,  as  before,  it  is  turned  off'  by  a  muscular  valve 
into  the  second  stomach,  or  reticulum  (c),  which  is  distinguished 
by  the  intersecting  folds  of  its  mucous  membrane,  which  give  it 


/ 


i 


Alimentaky  Canal  op 
Fowl.  —  n.  OSsophagus.  6. 
Crop.  c.  Proventriculus,  or 
secreting  stomach,  d.  Gizzard, 
or  triturating  stomach,  e.  In- 
testine. /.  Two  long  csBcal 
tubes  which  open  into  the  in- 
testine a  short  distance  above 
its  termination. 


118 


DIGESTION. 


Compound  Stomach  of  Ox.  —  n.  (Esopha- 
gus 6.  Eumen,  or  first  stomach,  c.  Reticulum,  or 
second,  d.  Omasus,  or  third.  «.  Abomasus,  or 
fourth.    /.  Duodenum.     (From  Eymer  Jones.) 


a  honey-combed  or  reticulated  appearance.     Here  the  food,  already 

triturated   in  the   mouth,   and 
^'°'  mixed  with  the  saliva,  is  further 

macerated  in  the  fluids  swal- 
lowed by  the  animal,  which  al- 
ways accumulate  in  considerable 
quantity  in  the  reticulum.  The 
next  cavity  is  the  omasus,  or 
'•'  psalterium"  {d),  in  which  the 
mucous  membrane  is  arranged 
in  longitudinal  folds,  alternately 
broad  and  narrow,  lying  parallel 
with  each  other  like  the  leaves 
of  a  book,  so  that  the  extent  of 
mucous  surface,  brought  in  con- 
tact with  the  food,  is  very  much 
increased.  The  exit  from  this 
cavity  leads  directly  into  the 
abomasus,  or  "  rennet"  (e),  which 
is  the  true  digestive  stomach,  in  which  the  mucous  membrane  is 
softer,  thicker,  and  more  glandular  than  elsewhere,  and  in  which 
an  acid  and  highly  solvent  fluid  is  secreted.  Then  follows  the  in- 
testinal canal  with  its  various  divisions  and  variations. 

In  the  carnivora,  on  the  other  hand,  the  alimentary  canal  is 
shorter  and  narrower  than  in  the  preceding,  and  presents  fewer 
complexities.  The  food,  upon  which  these  animals  subsist,  is  softer 
than  that  of  the  herbivora,  and  less  encumbered  with  indigestible 
matter ;  so  that  the  process  of  its  solution  requires  a  less  extensive 
apparatus. 

In  the  human  species,  the  food  is  naturally  of  a  mixed  cha- 
racter, containing  both  animal  and  vegetable  substances.  But  the 
digestive  apparatus  in  man  resembles  almost  exactly  that  of  the 
carnivora.  For  the  vegetable  matters  which  we  take  as  food  are, 
in  the  first  place,  artificially  separated,  to  a  great  extent,  from  indi- 
gestible impurities ;  and  secondly,  they  are  so  softened  by  the 
process  of  cooking  as  to  become  nearly  or  quite  as  easily  digestible 
as  animal  substances. 

In  the  human  species,  however,  the  process  of  digestion,  though 
simpler  than  in  the  herbivora,  is  still  complicated.  The  alimentary 
canal  is  here,  also,  divided  into  different  compartments  or  cavities, 
which  communicate  with  each  other  by  narrow  orifices.     At  its 


DIGESTION". 


119 


commencement  (Fig.  18),  we  find  tlie  cavity  of  tlie  mouth,  which  is 
guarded  at  its  posterior  extremity  by  the  muscular  valve  of  the 
isthmus     of     the     fauces.  pjg_  jg^ 

Through  the  pharynx  and 
oesophagus  (a),  it  commu- 
nicates with  the  second 
compartment,  or  the  sto- 
mach (h),  a  flask-shaped 
dilatation,  which  is  guarded 
at  the  cardiac  and  pyloric 
orifices  by  circular  bands 
of  muscular  fibres.  Then 
comes  the  small  intestine  (e), 
different  parts  of  which, 
owing  to  the  varying  struc- 
ture of  their  mucous  mem- 
branes, have  received  the 
different  names  of  duode- 
num, jejunum,  and  ileum. 
In  the  duodenum  we  have 
the  orifices  of  the  biliary 
and  pancreatic  ducts  {f,  g). 
Finally,  we  have  the  large 
intestine  (h,  i,j,  Jc),  separated 
from  the  smaller  by  the 
ileo-caecal  valve,  and  ter- 
minating, at  its  lower  ex- 
tremity, by  the  anus,  at 
which  is  situated  a  double 
sphincter,  for  the  purpose 
of  guarding  its  orifice. 
Everywhere  the  alimentary 
canal  is  composed  of  a 
mucous  membrane  and  a 
muscular  coat,  with  a  layer 
of  submucous  areolar  tissue 
between  the  two.  The  mus- 
cular coat  is  everywhere 
composed  of  a  double  layer  of  longitudinal  and  transverse  fibres, 
by  the  alternate  contraction  and  relaxation  of  which  the  food  is 
carried   through  the  canal   from  above  downward.     The  mucous 


HuMAK  Alimentary  Canal.  —  a.  CEsoplia^ns. 
b.  Stomach,  c.  Cardiac  orifice,  d.  Pylorus,  e.  Small 
Intestine.  /.  Biliary  duct.  </.  Pancreatic  duct.  h.  As- 
cending colon,  i.  Transverse  colon.  J.  Descending 
colon,     k.  Rectum. 


120  DIGESTION. 

membrane  presents,  also,  a  different  structure,  and  has  different 
properties  in  different  parts.  In  the  mouth  and  oesophagus,  it  is 
smooth,  with  a  hard,  whitish,  and  tessellated  epithelium.  This  kind 
of  epithelium  terminates  abruptly  at  the  cardiac  orifice  of  the 
stomach.  The  mucous  membrane  of  the  gastric  cavity  is  soft  and 
glandular,  covered  with  a  transparent,  columnar  epithelium,  and 
thrown  into  minute  folds  or  projections  on  its  free  surface,  which 
are  sometimes  reticulated  with  each  other.  In  the  small  intestine, 
we  find  large  transverse  folds  of  mucous  membrane,  the  valvulse 
conniventes,  the  minute  villosities  which  cover  its  surface,  and  the 
peculiar  glandular  structures  which  it  contains.  Finally,  in  the 
large  intestine,  the  mucous  membrane  is  again  different.  It  is  here 
smooth  and  shining,  free  from  villosities,  and  provided  with  a  dif- 
ferent glandular  apparatus. 

Furthermore,  the  digestive  secretions,  also,  vary  in  these  different 
regions.  In  its  passage  from  above  downward,  the  food  meets 
with  no  less  than  five  different  digestive  fluids.  First  it  meets  with 
the  saliva  in  the  cavity  of  the  mouth ;  second,  with  the  gastric  juice, 
in  the  stomach ;  third,  with  the  hile ;  fourth,  with  the  pancreatic 
fluid;  and  fifth,  with  the  intestinal  juice.  It  is  the  most  important 
characteristic  of  the  process  of  digestion,  as  established  by  modern 
researches,  that  different  elements  of  the  food  are  digested  in  different 
jMrts  of  the  alimentary  canal  hy  the  agency  of  different  digestive  fluids. 
By  their  action,  the  various  ingredients  of  the  alimentary  mass  are 
successively  reduced  to  a  fluid  condition,  and  are  taken  up  by  the 
vessels  of  the  intestinal  mucous  membrane. 

The  action  which  is  exerted  upon  the  food  by  the  digestive 
fluids  is  not  that  of  a  simple  chemical  solution.  It  is  a  transforma- 
tion, by  which  the  ingredients  of  the  food  are  altered  in  character 
at  the  same  time  that  they  undergo  the  process  of  liquefaction. 
The  active  agent  in  producing  this  change  is  in  every  instance  an 
organic  matter,  which  enters  as  an  ingredient  into  the  digestive 
fluid ;  and  which,  by  coming  in  contact  with  the  food,  exerts  upon 
it  a  catalytic  action,  and  transforms  its  ingredients  into  other  sub- 
stances. It  is  these  newly  formed  substances  which  are  finally 
absorbed  by  the  vessels,  and  mingled  with  the  general  current  of 
the  circulation. 

In  our  study  of  the  process  of  digestion,  the  different  digestive 
fluids  will  be  examined  separately,  and  their  action  on  the  aliment- 
ary substances  in  the  different  regions  of  the  digestive  apparatus 
successively  investigated. 


MASTICATION'.  121 

Mastication. — In  the  first  division  of  the  alimentary  canal,  viz., 
the  mouth,  the  food  undergoes  simultaneously  two  different  opera- 
tions, viz.,  mastication  and  insalivation.  Mastication  consists  in 
the  cutting  and  trituration  of  the  food  by  the  teeth,  by  the  action 
of  which  it  is  reduced  to  a  state  of  minute  subdivision.  This  pro- 
cess is  entirely  a  mechanical  one.  It  is  necessary,  in  order  to  pre- 
pare the  food  for  the  subsequent  action  of  the  digestive  fluids.  As 
this  action  is  chemical  in  its  nature,  it  will  be  exerted  more  promptly 
and  efficiently  if  the  food  be  finely  divided  than  if  it  be  brought  in 
contact  with  the  digestive  fluids  in  a  solid  mass.  This  is  always 
the  case  when  a  solid  body  is  subjected  to  the  chemical  action  of  a 
solvent  fluid;  since,  by  being  broken  up  into  minute  particles,  it 
offers  a  larger  surface  to  the  contact  of  the  fluid,  and  is  more  readily 
attacked  and  dissolved  or  decomposed  by  it. 

In  the  structure  of  the  teeth,  and  their  physiological  action,  there 
are  certain  marked  differences,  corresponding  with  the  habits  of  the 
animal,  and  the  kind  of  food  upon  which  it  subsists.  In  fish  and 
serpents,  in  which  the  food  is  swallowed  entire,  and  in  which  the 
process  of  digestion,  accordingly,  is  comparatively  slow,  the  teeth 
are  simply  organs  of  prehension.  They  have  generally  the  form 
of  sharp,  curved  spines,  with  their  points  set  backward  (Fig.  19), 
and  arranged  in  a  double  or  triple  row 
about  the  edges  of  the  jaws,  and  sometimes  ^  ^* 

covering  the  mucous  surfaces  of  the  mouth, 
tongue,  and  palate.  They  serve  merely  to 
retain  the  prey,  and  prevent  its  escape, 
after  it  has  been  seized  by  the  animal.  In 
the  carnivorous  quadrupeds,  as  those  of      skull  op  rattlesnake. 

,1         T  1  ,     1   •      T  T  1  •      .1  (After  Achille-Eicliai'd.) 

the  dog  and  cat  kind,  and  other  similar 

families,  there  are  three  different  kinds  of  teeth  adapted  to  different 
mechanical  purposes.  (Fig.  20.)  First,  the  incisors,  twelve  in  num- 
ber, situated  at  the  anterior  part  of  the  jaw,  six  in  the  superior, 
and  six  in  the  inferior  maxilla,  of  flattened  form,  and  placed  with 
their  thin  edges  running  from  side  to  side.  The  incisors,  as  their 
name  indicates,  are  adapted  for  dividing  the  food  by  a  cutting 
motion,  like  that  of  a  pair  of  shears.  Behind  them  come  the  canine 
teeth,  or  tusks,  one  on  each  side  of  the  upper  and  under  jaw. 
These  are  long,  curved,  conical,  and  pointed;  and  are  used  as 
weapons  of  offence,  and  for  laying  hold  of  and  retaining  the  pre3^ 
Lastly,  the  molars,  eight  or  more  in  number  on  each  side,  are 
larger  and  broader  than  the  incisors,  and  provided  with  serrated 


122 


DIGESTION. 


edges,  each  presenting  several  sharp  points,  arranged  generally  in 
a  direction  parallel  with  the  line  of  the  jaw.     In  these  animals, 

mastication  is  very  imperfect,  since 
the  food  is  not  ground  tip,  but  only 
pierced  and  mangled  by  the  action 
of  the  teeth  before  being  swallowed 
into  the  stomach.  In  the  herbi- 
vora,  on  the  other  hand,  the  inci- 
sors are  present  only  in  the  lower 
jaw  in  the  ruminating  animals, 
though  in  the  horse  they  are  found 
in  both  the  upper  and  lower  max- 
illa, (Fig.  21.)  They  are  used  merely 
for  cutting  off  the  bundles  of  grass 
or  herbage,  on  which  the  animal  feeds.  The  canines  are  either 
absent  or  slightly  developed,  and  the  real  process  of  mastication  is 


Skttll    op   Polar    Bear.       Anterior 
▼iew;  showing  incisors  and  cauines. 


Fig.  21. 


Skpli.  of  the  Hosss. 


performed  altogether  by  the  molars.  These  are  large  and  thick 
(Fig.  22),  and  present  a  broad,  flat  surface,  diversified  by  variously 
folded  and  projecting  ridges  of  enamel,  with  shal- 
low grooves,  intervening  between  them.  By  the 
lateral  rubbing  motion  of  the  roughened  surfaces 
against  each  other,  the  food  is  effectually  commi- 
nuted and  reduced  to  a  pnlpy  mass. 

In  the  human  subject,  the  teeth  combine  the 
characters  of  those  of  the  carnivora  and  the  herbi- 
vora.  (Fig.  23.)  The  incisors  (a),  four  in  number 
in  each  jaw,  have,  as  in  other  instances,  a  cutting 


Molar  Tooth  of 
THE    Horse.     Grind- 

\ut,'  surface. 


SALIVA. 


128 


Fi-.  23. 


^-:' 


Human  Teeth  — Uppek  Jaw.— a.  Incisors.    5.  Canines 
.  Anterior  molars,     d.  Posterior  molars. 


edge  running  from  side  to  side.  The  canines  (i),  which  are  situated 
immediately  behind  the  former,  are  much  less  prominent  and 
pointed  than  in  the  car- 
nivora,  and  differ  less 
in  form  from  the  inci- 
sors on  the  one  hand, 
and  the  first  molars  on 
the  other.  The  molars, 
again  (c,  d),  are  thick 
and  strong,  and  have 
comparatively  flat  sur- 
faces, like  those  of  the 
herbivora;  but  instead 
of  presenting  curvili- 
near ridges,  are  covered 
with  more  or  less  coni- 
cal eminences,  like  those 
of  the  carni  vora.  In  the 
human  subject,  therefore,  the  teeth  are  evidently  adapted  for  a  mixed 
diet,  consisting  of  both  animal  and  vegetable  food.  Mastication  is 
here  as  perfect  as  it  is  in  the  herbivora,  though  less  prolonged  and 
laborious ;  for  the  vegetable  substances  used  by  man,  as  already 
remarked,  are  previously  separated  to  a  great  extent  from  their 
impurities,  and  softened  by  cooking ;  so  that  they  do  not  require, 
for  their  mastication,  so  extensive  and  powerful  a  triturating  ap- 
paratus. Finally,  animal  substances  are  more  completely  masti- 
cated in  the  human  subject  than  they  are  in  the  carnivora,  and 
their  digestion  is  accordingly  completed  with  greater  rapidity. 

We  can  easily  estimate,  from  the  facts  above  stated,  the  great 
importance,  to  the  digestive  process,  of  a  thorough  preliminary 
mastication.  If  the  food  be  hastily  swallowed  in  undivided  masses, 
it  must  remain  a  long  time  undissolved  in  the  stomach,  where  it 
will  become  a  source  of  irritation  and  disturbance ;  but  if  reduced 
beforehand,  by  mastication,  to  a  state  of  minute  subdivision,  it  is 
readily  attacked  by  the  digestive  fluids,  and  becomes  speedily  and 
completely  liquefied. 


Saliva. — At  the  same  time  that  the  food  is  masticated,  it  is  mixed 
in  the  cavity  of  the  mouth  with  the  first  of  the  digestive  fluids,  viz., 
the  saliva.  Human  saliva,  as  it  is  obtained  directly  from  the  buc- 
cal cavity,  is  a  colorless,  slightly  viscid  and  alkaline  fluid,  with  a 


124  DIGESTION. 

specific  gravity  of  1005.  When  first  discharged,  it  is  frothy  and 
opaline,  holding  in  suspension  minute,  whitish  flocculi.  On  being 
allowed  to  stand  for  some  hours  in  a  cylindrical  glass  vessel,  an 
opaque,  whitish  deposit  collects  at  the  bottom,  while  the  supernatant 
fluid  becomes  clear.  The  deposit,  when  examined  by  the  micro- 
„.    24  scope  (Fig.   24),  is    seen   to 

consist   of  abundant  ejDithe- 
lium  scales  from  the  internal 
^*>^^^  ^__;g5N      <   ^    \  surface   of    the    mouth,   de- 

;:,ft^-fy;«A?":;:,.   '    '    I  /f-     \       tached  by  mechanical  irrita- 
/  . .  te!&:Sl;SEfe[||^^:,:^,,^|  ■'^       \      tion,  minute,  roundish,    gra- 

Pnolar,  nucleated  cells,  appa- 
rently epithelium   from   the 
mucous    follicles,   a    certain 
/    amount  of  granular  matter, 
'©      pmll      j  "(P  ^     /     and  a  few  oil-globules.     The 
O  %fefiSiW   °       /       supernatant  fluid  has  a  faint 
^    ^^^      "      o        /  bluish    tinge,    and    becomes 

slightly  opalescent   by  boil- 
BaccALA>-DG.Ax„u,,AKEP,THEMtiM,wuh   iug, _ aud  by  thc  addition  of 

Granular  Matter  and  Oil-globules;  deposited  as  sedi-     nitric    acid.       Alcohol    iu    CX- 
meut  from  human  saliva.  r\  *     -j.    i."    „ 

cess  causes  the  precipitation 
of  abundant  whitish  flocculi.  According  to  Bidder  and  Schmidt,^ 
the  composition  of  saliva  is  as  follows: — 

Composition  of  Saliva. 

Water 995.16 

Organic  matter            .         •         .         •         •         •         •         •         •  1.34 

Sulpho-cyanide  of  potassium 0.06 

Phosphates  of  soda,  lime,  and  magnesia -98 

Chlorides  of  sodium  and  potassium -84 

Mixture  of  epithelium \.'a1 

lUOO.OO 

The  organic  substance  present  in  the  saliva  has  been  occasionally 
known  by  the  name  of  ptyaline.  It  is  coagulable  by  alcohol,  but 
not  by  a  boiling  temperature.  A  very  little  albumen  is  also  pre- 
sent, mingled  with  the  pty aline,  and  produces  the  opalescence 
which  appears  in  the  saliva  when  raised  to  a  boiling  temperature. 
The  sulpho-cyanogen  may  be  detected  by  a  solution  of  chloride  of 
iron,  which  produces  the  characteristic  red  color  of  sulpho-cyanide 

'  Verdauungsssefte  und  Stoffwechsel.     Leipzig,  1852. 


SALIVA.  125 

of  iron.  The  alkaline  reaction  of  the  saliva  varies  in  intensity 
during  the  day,  but  is  nearly  always  sufficiently  distinct. 

The  saliva  is  not  a  simple  secretion,  but  a  mixture  of  four  dis- 
tinct fluids,  which  differ  from  each  other  in  the  source  from  which 
they  are  derived,  and  in  their  physical  and  chemical  properties. 
These  secretions  are,  in  the  human  subject,  first,  that  of  the  parotid 
gland ;  second,  that  of  the  submaxillary ;  third,  that  of  the  sub- 
lingual ;  and  fourth,  that  of  the  mucous  follicles  of  the  mouth. 
These  different  fluids  have  been  comparatively  studied,  in  the 
lower  animals,  by  Bernard,  Frerichs,  and  Bidder  and  Schmidt. 
The  parotid  saliva  is  obtained  in  a  state  of  purity  from  the  dog  by 
exposing  the  duct  of  Steno  where  it  crosses  the  masseter  muscle, 
and  introducing  into  it,  through  an  artificial  opening,  a  fine  silver 
canula.  The  parotid  saliva  then  runs  directly  from  its  external 
orifice,  without  being  mixed  with  that  of  the  other  salivary  glands. 
It  is  clear,  limpid,  and  watery,  without  the  slightest  viscidity,  and 
has  a  faintly  alkaline  I'eaction.  The  submaxillary  saliva  is  ob- 
tained in  a  similar  manner,  by  inserting  a  canula  into  Wharton's 
duct.  It  differs  from  the  parotid  secretion,  so  far  as  its  physical 
properties  are  concerned,  chiefly  in  possessing  a  well-marked  vis. 
cidity.  It  is  alkaline  in  reaction.  The  sublingual  saliva  is  also 
alkaline,  colorless,  and  transparent,  and  possesses  a  greater  degree 
of  viscidity  than  that  from  the  submaxillary.  The  mucous  secre- 
tion  of  the  follicles  of  the  mouth,  which  forms  properly  a  part  of 
the  saliva,  is  obtained  by  placing  a  ligature  simultaneously  on 
Wharton's  and  Steno's  ducts,  and  on  that  of  the  sublingual  gland, 
so  as  to  shut  out  from  the  mouth  all  the  glandular  salivary  secre- 
tions, and  then  collecting  the  fluid  secreted  by  the  buccal  mucous 
membrane.  This  fluid  is  very  scanty,  and  much  more  viscid  than 
either  of  the  other  secretions ;  so  much  so,  that  it  cannot  be  poured 
out  in  drops  when  received  in  a  glass  vessel,  but  adheres  strongly 
to  the  surface  of  the  glass. 

We  have  obtained  the  imrotid  saliva  of  the  human  subject  in  a 
state  of  purity  by  introducing  directly  into  the  orifice  of  Steno's 
duct  a  silver  canula  ^^5  to  ^V  of  ^^  iiich  in  diameter.  The  other 
extremity  of  the  canula  projects  from  the  mouth,  between  the  lips, 
and  the  saliva  is  collected  as  it  runs  from  the  open  orifice.  This 
method  gives  results  much  more  valuable  than  observations  made 
on  salivary  fistulas  and  the  like,  since  the  secretion  is  obtained 
under  perfectly  healthy  conditions,  and  unmixed  with  other  animal 
fluids. 


126  DIGESTION. 

The  result  of  many  different  observations,  conducted  in  this  way, 
is  that  the  human  parotid  saliva,  like  that  of  the  dog,  is  colorless, 
watery,  and  distinctly  alkaline  in  reaction.  It  differs  from  the  mixed 
saliva  of  the  mouth,  in  being  perfectly  clear,  without  any  turbidity 
or  opalescence.  Its  flow  is  scanty  while  the  cheeks  and  jaws  remain 
at  rest  •  but  as  soon  as  the  movements  of  mastication  are  excited  by 
the  introduction  of  food,  it  runs  in  much  greater  abundance.  We 
have  collected,  in  this  way,  from  the  parotid  duct  of  one  side  only, 
in  a  healthy  man,  480  grains  of  saliva  in  the  course  of  twenty 
minutes ;  and  in  seven  successive  observations,  made  on  different 
days,  comprising  in  all  three  hours  and  nine  minutes,  we  have 
collected  a  little  over  3000  grains. 

The  parotid  saliva  obtained  in  this  way  has  been  analyzed  by 
Mr.  Maurice  Perkins,  Assistant  to  the  Professor  of  Chemistry  in 
the  College  of  Physicians  and  Surgeons,  with  the  following  result : — 

Composition  of  Human  Parotid  Saliva. 

Water 983.300 

Organic  matter  precipitable  by  alcohol       .....  7.352 
Substance  destructible  by  heat,  but  not  precipitated  by  alcohol 

or  acids  ...........  4.81 

Sulpho-cyanide  of  sodium 0.33 

Phosphate  of  lime      .........  0.24 

Chloride  of  potasr^ium         ........  0.90 

Chloride  of  sodium  and  carbonate  of  soda           ....  3.06 

1000.00 

Mr.  Perkins  found,  in  accordance  with  our  own  observations, 
that  the  fresh  parotid  saliva,  when  treated  with  perch! oride  of  iron, 
showed  no  evidences  of  sulpho-cyanogen ;  but  after  the  organic  mat- 
ters had  been  precipitated  by  alcohol,  the  filtered  fluid  was  found 
to  contain  an  appreciable  quantity  of  the  sulpho-cyanide. 

The  organic  matter  in  the  parotid  saliva  is  in  rather  large  quan- 
tity as  compared  with  the  mineral  ingredients.  It  is  precipitable  by 
alcohol,  by  a  boiling  temperature,  by  nitric  acid,  and  by  sulphate 
of  soda  in  excess,  but  not  by  an  acidulated  solution  of  ferrocyanide 
of  potassium.  It  bears  some  resemblance,  accordingly,  to  albumen, 
but  yet  is  not  precisely  identical  with  that  substance. 

The  parotid  saliva  also  differs  from  the  mixed  saliva  of  the  mouth 
in  containiDg  some  substance  which  masks  the  reaction  of  sulpho- 
cyanogen.  For  if  the  parotid  saliva  and  that  from  the  mouth  be 
drawn  from  the  same  person  within  the  same  hour,  the  addition  of 
perchloride  of  iron  will  produce  a  distinct  red  color  in  the  latter,  while 
no  such  change  takes  place  in  the  former.     And  yet  the  parotid 


SALIVA.  127 

saliva  contains  sulpho-cyanogen,  which  may  be  detected,  as  we  "have 
already  seen,  after  the  organic  matters  have  been  precipitated  by 
alcohol. 

A  very  curious  fact  has  been  observed  by  M.  Colin,  Professor  of 
Anatomy  and  Physiology  at  the  Veterinary  School  of  Alfort,^  viz., 
that  in  the  horse  and  ass,  as  well  as  in  the  cow  and  other  ruminat- 
ing animals,  the  parotid  glands  of  the  two  opposite  sides,  during 
mastication,  are  never  in  active  secretion  at  the  same  time ;  but 
that  they  alternate  with  each  other,  one  remaining  quiescent  while 
the  other  is  active,  and  vice  versa.  In  these  animals  mastication  is 
said  to  be  unilateral,  that  is,  when  the  animal  commences  feeding 
or  ruminating,  the  food  is  triturated,  for  fifteen  minutes  or  more,  by 
the  molars  of  one  side  only.  It  is  then  changed  to  the  opposite 
side ;  and  for  the  next  fifteen  minutes  mastication  is  performed  by 
the  molars  of  that  side  only.  It  is  then  changed  back  again,  and 
so  on  alternately,  so  that  the  direction  of  the  lateral  movements  of 
the  jaw  may  be  reversed  many  times  during  the  course  of  a  meal. 
By  establishing  a  salivary  fistula  simultaneously  on  each  side,  it  is 
found  that  the  flow  of  saliva  corresponds  with  the  direction  of  the 
masticatory  movement.  When  the  animal  masticates  on  the  right 
side,  it  is  the  right  parotid  which  secretes  actively,  while  but  little 
saliva  is  supplied  by  the  left ;  when  mastication  is  on  the  left  side, 
the  left  parotid  pours  out  an  abundance  of  fluid,  while  the  right  is 
nearly  inactive. 

We  have  observed  a  similar  alternation  in  the  flow  of  parotid 
saliva  in  the  human  subject,  when  the  mastication  is  changed  from 
side  to  side.  In  an  experiment  of  this  kind,  the  tube  being  inserted 
into  the  parotid  duct  of  the  left  side,  the  quantity  of  saliva  dis- 
charged during  twenty  minutes,  while  mastication  was  performed 
mainly  on  the  opposite  side  of  the  mouth,  was  127.5  grains ;  while 
the  quantity  during  the  same  period,  mastication  being  on  the  same 
side  of  the  mouth,  was  374.4  grains — being  nearly  three  times  as 
much  in  the  latter  case  as  in  the  former. 

Owing  to  the  variations  in  the  rapidity  of  its  secretion,  and  also 
to  the  fact  that  it  is  not  so  readily  excited  by  artificial  means  as 
by  the  presence  of  food,  it  becomes  somewhat  difficult  to  estimate 
the  total  quantity  of  saliva  secreted  daily.  The  first  attempt  to  do  so 
was  made  by  Mitscherlich,^  who  collected  from  two  to  three  ounces 
in  twenty-four  hours  from  an  accidental  salivary  fistula  of  Steno's 

'  Traite  de  Pliysiologie  Comparee,  Paris,  1854,  p.  468. 
'  SiiLiou's  Chemistry  of  Man.     Phila.  ed.,  1840,  p.  295. 


128  DIGESTION. 

duct  in  tlie  liuinaii  subject ;  from  whicli  it  was  supposed  that  the 
total  amount  secreted  by  all  the  glands  was  from  ten  to  twelve 
ounces  daily.  As  this  man  was  a  hospital  patient,  hoAvever,  and 
suffering  from  constitutional  debility,  the  above  calculation  cannot 
be  regarded  as  an  accurate  one,  and  accordingly  Bidder  and  Schmidt^ 
make  a  higher  estimate.  One  of  these  observers,  in  experimenting 
upon  himself,  collected  from  the  mouth  in  one  hour,  without  using 
any  artificial  stimulus  to  the  secretion,  1500  grains  of  saliva ;  and 
calculates,  therefore,  the  amount  secreted  daily,  making  an  allow- 
ance of  seven  hours  for  sleep,  as  not  far  from  25,000  grains,  or 
about  three  and  a  half  pounds  avoirdupois. 

On  repeating  this  experiment,  however,  we  have  not  been  able  to 
collect  from  the  mouth,  without  artificial  stimulus,  more  than  556 
grains  of  saliva  per  hour.  This  quantity,  however,  may  be  greatly 
increased  by  the  introduction  into  the  mouth  of  any  smooth  un- 
irritating  substance,  as  glass  beads  or  the  like;  and  during  the 
mastication  of  food,  the  saliva  is  poured  out  in  Yery  much  greater 
abundance.  The  very  sight  and  odor  of  nutritious  food,  when  the 
appetite  is  excited,  will  stimulate  to  a  remarkable  degree  the  flow 
of  saliva ;  and,  as  it  is  often  expressed,  "  bring  the  water  into  the 
mouth."  Any  estimate,  therefore,  of  the  total  quantity  of  saliva, 
based  on  the  amount  secreted  in  the  intervals  of  mastication,  would 
be  a  very  imperfect  one.  We  may  make  a  tolerably  accurate 
calculation,  however,  by  ascertaining  how  much  is  really  secreted 
during  a  meal,  over  and  above  that  which  is  produced  at  other  times. 
"We  have  found,  for  example,  by  experiments  performed  for  this 
purpose,  that  wheaten  bread  gains  during  complete  mastication  55 
per  cent,  of  its  weight  of  saliva ;  and  that  fresh  cooked  meat  gains, 
under  the  same  circumstances,  48  per  cent,  of  its  weight.  We  have 
already  seen  that  the  daily  allowance  of  these  two  substances,  for  a 
man  in  full  health,  is  19  ounces  of  bread,  and  16  ounces  of  meat. 
The  quantity  of  saliva,  then,  required  for  the  mastication  of  these 
two  substances,  is,  for  the  bread  4,572  grains,  and  for  the  meat  3,360 
grains.  If  we  now  calculate  the  quantity  secreted  between  meals 
as  continuing  for  22  hours  at  556  grains  per  hour,  we  have : — 

Saliva  required  for  mastication  of  bread  =    4572  grains. 
"  "  "  "  "  meat  =    3360      " 

secreted  in  intervals  of  meals  =  ]  2232      " 


Total  quantity  in  twenty-four  hours  =  20164  grains  ; 
or  rather  less  than  3  pounds  avoirdupois. 

'  Op.  cit.,  p.  14. 


SALIVA.  129 

The  most  important  question,  connected  with  this  subject,  relates 
to  ^e  function  of  the  saliva  in  the  digestive  process.  A  very  remark- 
able property  of  this  fluid  is  that  which  was  discovered  by  Leuchs 
in  Germany,  viz.,  that  it  possesses  the  power  of  converting  boiled 
starch  into  sugar,  if  mixed  with  it  in  equal  proportions,  and  kept 
for  a  short  time  at  the  temperature  of  100°  F.  This  phenomenon 
is  one  of  catalysis,  in  which  the  starch  is  transformed  into  sugar  by 
simple  contact  with  the  organic  substance  contained  in  the  saliva. 
This  organic  substance,  according  to  the  experiments  of  Mialhe,^ 
may  even  be  precipitated  by  alcohol,  and  kept  in  a  dry  state  for  an 
indefinite  length  of  time  without  losing  the  power  of  converting 
starch  into  sugar,  when  again  brought  in  contact  with  it  in  a  state 
of  solution. 

This  action  of  ordinary  human  saliva  on  boiled  starch  takes  place 
sometimes  with  great  rapidity.  Traces  of  glucose  may  occasionally 
be  detected  in  the  mixture  in  one  minute  after  the  two  substances 
have  been  brought  in  contact ;  and  we  have  even  found  that  starch 
paste,  introduced  into  the  cavity  of  the  mouthy  if  already  at  the 
temperature  of  100°  F,,  will  yield  traces  of  sugar  at  the  end  of  half 
a  minute.  The  rapidity  however,  with  which  this  action  is  mani- 
fested, varies  very  much,  as  was  formerly  noticed  by  Lehmann,  at 
different  times ;  owing,  in  all  probability,  to  the  varying  constitution 
of  the  saliva  itself.  It  is  often  impossible,  for  example,  to  find  any 
evidences  of  sugar,  in  the  mixture  of  starch  and  saliva,  under  five, 
ten,  or  fifteen  minutes ;  and  it  is  frequently  a  longer  time  than  this 
before  the  whole  of  the  starch  is  completely  transformed.  Even 
when  the  conversion  of  the  starch  commences  very  promptly,  it  is 
often  a  long  time  before  it  is  finished.  If  a  thin  starch  paste,  for 
example,  which  contains  no  traces  of  sugar,  be  taken  into  the  mouth 
and  thoroughly  mixed  with  the  buccal  secretions,  it  will  often,  as 
already  mentioned,  begin  to  show  the  reaction  of  sugar  in  the  course 
of  half  a  minute ;  but  some  of  the  starchy  matter  still  remains,  and 
will  continue  to  manifest  its  characteristic  reaction  with  iodine,  for 
fifteen  or  twenty  minutes,  or  even  half  an  hour. 

It  was  supposed,  when  this  property  of  converting  starch  into 
sugar  was  first  discovered  in  the  saliva,  that  it  constituted  the  true 
physiological  action  of  this  secretion,  and  that  the  function  of  the 
saliva  was,  in  reality,  the  digestion  and  liquefaction  of  starchy 
substances.     It  was  very  soon   noticed,  however,  by  the  French 

'  Chimie  appliquee  ^  la  Physiologic  et  %  la  Therapeutique,  Paris,  1856,  p.  43. 

9 


130  DIGESTIOX. 

observers,  tliat  this  property  of  tlie  saliva  was  ratiier  an  accidental 
than  an  essential  one;  and  that,  although  starchy  substances  are 
really  converted  into  sugar,  if  mixed  with  saliva  in  a  test-tube, 
yet  they  are  not  affected  by  it  to  the  same  degree  in  the  natural 
process  of  digestion,  "We  have  already  mentioned  the  extremely 
variable  activity  of  the  saliva,  in  this  respect,  at  different  times ; 
and  it  must  be  recollected,  also,  that  in  digestion  the  food  is  not 
retained  in  the  cavity  of  the  mouth,  but  passes  at  once,  after  mas- 
tication, into  the  stomach.  Several  German  observers,  as  Frerichs, 
Jacubowitsch,  Bidder  and  Schmidt,  maintained  at  first  that  the 
saccharine  conversion  of  starch,  after  being  commenced  in  the 
mouth,  might  be,  and  actually  was,  completed  in  the  stomach.  "We 
have  convinced  ourselves,  however,  by  frequent  experiments,  that 
this  is  not  the  case.  If  a  dog,  with  a  gastric  fistula,  be  fed  with  a 
mixture  of  meat  and  boiled  starch,  and  portions  of  the  fluid  con- 
tents of  the  stomach  withdrawn  afterward  through  the  fistula, 
the  starch  is  easily  recognizable  by  its  reaction  with  iodine  for  ten, 
fifteen,  and  twenty  minutes  afterward.  In  forty-five  minutes  it  is 
diminished  in  quantity,  and  in  one  hour  has  usually  altogether  dis- 
appeared ;  but  no  sugar  is  to  be  detected  at  any  time.  Sometimes 
the  starch  disappears  more  rapidly  than  this ;  but  at  no  time,  accord- 
ing to  our  observations,  is  there  any  indication  of  the  presence  of 
sugar  in  the  gastric  fluids.  Bidder  and  Schmidt  have  also  concluded, 
from  subsequent  investigations,'  that  the  first  experiments  performed 
under  their  direction  by  Jacubowitsch  were  erroneous ;  and  it  is 
now  ackaowledged  by  them,  as  well  as  by  the  French  observers, 
that  sugar  cannot  be  detected  in  the  stomach,  after  the  introduction 
of  starch  in  any  form  or  by  any  method.  In  the  ordinary  process 
of  digestion,  in  fact,  starchy  matters  do  not  remain  long  enough  in 
the  mouth  to  be  altered  by  the  saliva,  but  pass  at  once  into  the  sto- 
mach. Here  they  meet  with  the  gastric  fluids,  which  become  min- 
gled with  them,  and  prevent  the  change  which  would  otherwise  be 
effected  by  the  saliva.  "We  have  found  that  the  gastric  juice  will 
iuterfere,  in  this  manner,  with  the  action  of  the  saliva  in  the  test- 
tube,  as  well  as  in  the  stomach.  If  two  mixtures  be  made,  one  of 
starch  and  saliva,  the  other  of  starch,  saliva,  and  gastric  juice,  and 
both  kept  for  fifteen  minutes  at  the  temperature  of  100°  F.,  in  the 
first  mixture  the  starch  will  be  promptly  converted  into  sugar,  while 
in  the  second  no  such  change  will  take  place.     The  above  action, 

'  Op  cit.,  p.  26. 


SALIVA.  131 

therefore,  of  saliva  on  starch,  though  a  curious  and  interesting  pro- 
perty, has  no  significance  as  to  its  physiological  function,  since  it 
does  not  take  place  in  the  natural  digestive  process.  We  shall  see 
hereafter  that  there  are  other  means  provided  for  the  digestion  of 
starchy  matters,  altogether  independent  of  the  action  of  the  saliva. 

The  true  function  of  the  saliva  is  altogether  a  physical  one.  Its 
action  is  simply  to  moisten  the  food  and  facilitate  its  mastication, 
as  well  as  to  lubricate  the  triturated  mass,  and  assist  its  passage 
down  the  oesophagus.  Food  which  is  hard  and  dry,  like  crusts, 
crackers,  &c.,  cannot  be  masticated  and  swallowed  with  readiness, 
unless  moistened  by  some  fluid.  If  the  saliva,  therefore,  be  prevented 
from  entering  the  cavity  of  the  mouth,  its  loss  does  not  interfere 
directly  with  the  chemical  changes  of  the  food  in  digestion,  but  only 
with  its  mechanical  preparation.  This  is  the  result  of  direct  experi- 
ments performed  by  various  observers.  Bidder  and  Schmidt,^  after 
tying  Steno's  duct,  together  with  the  common  duct  of  the  sub- 
maxillary and  sublingual  glands  on  both  sides  in  the  dog,  found 
that  the  immediate  effect  of  such  an  operation  was  "  a  remarkable 
diminution  of  the  fluids  which  exude  upon  the  surfaces  of  the  mouth ; 
so  that  these  surfaces  retained  their  natural  moisture  only  so  long 
as  the  mouth  was  closed,  and  readily  became  dry  on  exposure  to 
contact  with  the  air.  Accordingly,  deglutition  became  evidently 
difiicult  and  laborious,  not  only  for  dry  food,  like  bread,  but  even 
for  that  of  a  tolerably  moist  consistency,  like  fresh  meat.  The 
animals  also  became  very  thirsty,  and  were  constantly  ready  to 
drink." 

Bernard^  also  found  that  the  only  marked  effect  of  cutting  off 
the  flow  of  saliva  from  the  mouth  was  a  difficulty  in  the  mechani- 
cal processes  of  mastication  and  deglutition.  He  first  administered 
to  a  horse  one  pound  of  oats,  in  order  to  ascertain  the  rapidity  with 
which  mastication  would  naturally  be  accomplished.  The  above 
quantity  of  grain  was  thoroughly  masticated  and  swallowed  at  the 
end  of  nine  minutes.  An  opening  had  been  previously  made  in 
the  oesophagus  at  the  lower  part  of  the  neck,  so  that  none  of  the 
food  reached  the  stomach ;  but  each  mouthful,  as  it  passed  down  the 
oesophagus,  was  received  at  the  oesophageal  opening  and  examined 
by  the  experimenter.  The  parotid  duct  on  each  side  of  the  face 
was  then  divided,  and  another  pound  of  oats  given  to  the  animal. 
Mastication  and    deglutition  were  both  found  to  be  immediately 

'  Op.  cit.,p.  3. 

*  Le9ona  de  Physiologie  Experiuientale,  Paris,  1856,  p.  146. 


132  DIGESTION. 

retarded.  The  alimentary  masses  passed  down  the  oesophagus  at 
longer  intervals,  and  their  interior  was  no  longer  moist  and  pasty, 
as  before,  but  dry  and  brittle.  Finally,  at  the  end  of  twenty -five 
minutes,  the  animal  had  succeeded  in  masticating  and  swallowing 
only  about  three-quarters  of  the  quantity  which  he  had  previously 
disposed  of  in  nine  minutes. 

It  appears  also,  from  the  experiments  of  Magendie,  Bernard,  and 
Lassaigne,  on  horses  and  cows,  that  the  quantity  of  saliva  absorbed 
by  the  food  during  mastication  is  in  direct  proportion  to  its  hard- 
ness and  dryness,  but  has  no  particular  relation  to  its  chemical 
qualities.  These  experiments  were  performed  as  follows :  The  oeso- 
phagus was  opened  at  the  lower  part  of  the  neck,  and  a  ligature 
placed  upon  it,  between  the  wound  and  the  stomach.  The  animal 
was  then  supplied  with  a  previously  weighed  quantity  of  food,  and 
this,  as  it  passed  out  by  the  oesophageal  opening,  was  received  into 
appropriate  vessels  and  again  weighed.  The  difi'erence  in  weight, 
before  and  after  swallowing,  indicated  the  quantity  of  saliva  absorbed 
by  the  food.  The  following  table  gives  the  results  of  some  of  Las- 
saigne's  experiments,^  performed  upon  a  horse : — 

Kind  of  Food  employed.  Quantity  of  Saliva  absorbed. 

For  100  parts  of  hay  there  were  absorbed  400  parts  saliva. 

"  barley  meal  "  186  " 

"  oats  "  113  " 

"  green  stalks  and  leaves    "  49  " 

It  is  evident  from  the  above  facts,  that  the  quantity  of  saliva 
produced  has  not  so  much  to  do  with  the  chemical  character  of  the 
food  as  with  its  physical  condition.  When  the  food  is  dry  and 
hard,  and  requires  much  mastication,  the  saliva  is  secreted  in 
abundance ;  when  it  is  soft  and  moist,  a  smaller  quantity  of  the 
secretion  is  poured  out ;  and  finally,  when  the  food  is  taken  in  a 
fluid  form,  as  soup  or  milk,  or  reduced  to  powder  and  moistened 
artificially  with  a  very  large  quantity  of  water,  it  is  not  mixed  at 
all  with  the  saliva,  but  passes  at  once  into  the  cavity  of  the  stomach. 
The  abundant  and  watery  fluid  of  the  parotid  gland  is  most  useful 
in  assisting  mastication ;  while  the  glairy  and  mucous  secretion  of 
the  submaxillary  gland  and  the  muciparous  follicles  serve  to  lubri- 
cate the  exterior  of  the  triturated  mass,  and  facilitate  its  passage 
through  the  oesophagus. 

By  the  combined  operation  of  the  two  processes  which  the  food 
undergoes  in  the  cavity  of  the  mouth,  its  preliminary  preparation 

'  Comptes  Eendus,  vol.  xxi.  p.  362. 


GASTRIC    JUICE,    AND    STOMACH    DIGESTION". 


133 


ig  accomplished.  It  is  triturated  and  disintegrated  by  the  teeth, 
•and,  at  the  same  time,  by  the  movements  of  the  jaws,  tongue,  and 
^.heeks,  it  is  intimately  mixed  with  the  salivary  fluids,  until  the 
whole  is  reduced  to  a  soft,  pasty  mass,  of  the  same  consistency 
throughout.  It  is  then  carried  backward  by  the  semi-involuntary 
movements  of  the  tongue  into  the  pharynx,  and  conducted  by  the 
muscular  contractions  of  the  oesophagus  into  the  stomach. 

Gastric  Juice,  and  Stomach  Digestion.— The  mucous  mem- 
brane of  the  stomach  is  distinguished  by  its  great  vascularity 
and  the  abundant  glandular  apparatus  with  which  it  is  provided. 
Its  entire  thickness  is  occupied  by  certain  glandular  organs,  the 
gastric  tubules  or  follicles,  which  are  so  closely  set  as  to  leave 
almost  no  space  between  them  except  what  is  required  for  the 
capillary  bloodvessels.  The  free  surface  of  the  gastric  mucous 
membrane  is  not  smooth,  but  is  raised  in  minute  ridges  and  pro- 
jecting eminences.  In  the  cardiac  portion  (Fig.  25),  these  ridges 
are  reticulated  with  each  other,  .so  as  to  include  between  them 
polygonal  interspaces,  each  of  which  is  encircled  by  a  capillary 
network.    In  the  pyloric  portion  (Fig.  26),  the  eminences  are  more 


Fig.  25. 


Fig.  26. 


•Fig.  25.  Free  surface  of  Gastric  Mucous  Membrane,  viewed  from  above;  from  Pig's  Sto- 
macli,  Cardiuc  portion.     Magnified  70  diameters. 

Fig.  26.  Free  surface  of  Ga.stiuc  Mucous  Mrmbrane,  viewed  in  vertical  section;  from 
Pig  *  Stomach,  Pyloric  portioa.     Magnified  420  diameters. 

or  less  pointed  and  conical  in  form,  and  generally  flattened  from 
side  to  side.     They  contain  each  a  capillary  bloodvessel,  which  re- 


134 


DIGESTION. 


turns  upon  itself  in  a  loop  at  tlie  extremity  of  the  projection,  and 
communicates  freely  with  adjacent  vessels.    The  gastric  follicles  are 

very    different    in    different 
^•S-  2'^-  parts  of  the  stomach.    In  the 

pyloric  portion  (Fig.  27),  they 
are  nearly  straight,  simple 
tubules,  j{tj  of  an  inch  in 
diameter,  easily  separated 
from  each  other,  lined  with 
glandular  epithelium,  and  ter- 
minating in  blind  extremities 
at  the  under  surface  of  the 
mucous  membrane.  They  are 
sometimes  slightly  branched, 
or  provided  with  one  or  two 
ronnded  diverticula,  a  short 
distance  above  their  termina- 
tion. They  open  on  the  free 
surface  of  the  mncons  meni- 
brane,  in  the  interspaces  be- 
tween the  projecting  folds  or  villi.  Among  these  tubular  glandules 
there  is  also  found,  in  the  gastric  mucous  membrane,  another  kind 
of  glandular  organ,  consisting  of  closed  follicles,  similar  to  the  soli- 


Mucous  membrane  of  pig's  stomach,  from 

Pyloric  portion;  vertical  section;  showing  gastric 
tnbules,  and,  at  a,  a  closed  follicle.  Magnifie'd  70 
diameters. 


Fig.  28. 


F;g.  29. 


Fig.  28.  Gastric  Tubules  feom  Pig's  Stomach,  Pyloric  portion,  showing  their  Csecal 
Extremities.     At  a,  the  torn  extremity  of  a  tubule,  showing  its  cavity. 

Fig.  29.  Gastric  Tubules  from  Pig's  Stomach;  Cardiac  portion.  At  a,  a  large  tuhule 
dividing  into  two  small  ones.    6.  Portion  of  a  tubule,  seen  endwise,    e.  Its  central  cavity. 


GASTRIC    JUICE,    AND    STOMACH    DIGESTION.  135 

taiy  glands  of  tlie  small  intestine.  These  follicles,  whicli  are  not  very- 
numerous,  are  seated  in  the  lower  part  of  the  mucous  membrane, 
and  enveloped  by  the  csecal  extremities  of  the  tubules.  (Fig.  27,  a.) 

In  the  cardiac  portion  of  the  stomach,  the  tubules  are  very  wide 
in  the  superficial  part  of  the  mucous  membrane,  and  lined  with 
large,  distinctly  marked  cylinder  epithelium  cells.  (Fig.  29.)  In  the 
deeper  parts  of  the  membrane  they  become  branched  and  conside- 
rably reduced  in  size.  From  the  point  where  the  branching  takes 
place  to  their  termination  below,  they  are  lined  with  small  glandular 
epithelium  cells,  and  closely  bound  together  by  intervening  areolar 
tissue,  so  as  to  present  somewhat  the  appearance  of  compound 
glandules. 

The  bloodvessels  which  come  up  from  the  submucous  layer  of 
areolar  tissue  form  a  close  plexus  around  all  these  glandules,  and 
provide  the  mucous  membrane  with  an  abundant  supply  of  blood, 
for  the  purposes  both  of  secretion  and  absorption. 

That  part  of  digestion  which  takes  place  in  the  stomach  has 
always  been  regarded  as  nearly,  if  not  quite,  the  most  important 
part  of  the  whole  process.  The  first  observers  who  made  any 
approximation  to  a  correct  idea  of  gastric  digestion  were  Eeaumur 
and  Spallanzani,  who  showed  by  various  methods  that  the  reduction 
and  liquefaction  of  the  food  in  the  stomach  could  not  be  owing  to 
mere  contact  with  the  gastric  mucous  membrane,  or  to  compression 
by  the  muscular  walls  of  the  organ ;  but  that  it  must  be  attributed 
to  a  digestive  fluid  secreted  by  the  mucous  membrane,  which  pene- 
trates the  food  and  reduces  it  to  a  fluid  form.  They  regarded  this 
process  as  a  simple  chemical  solution,  and  considered  the  gastric 
juice  as  a  universal  solvent  for  all  alimentary  substances.  They 
succeeded  even  in  obtaining  some  of  this  gastric  juice,  mingled 
probably  with  many  impurities,  by  causing  the  animals  upon  which 
they  experimented  to  swallow  sponges  attached  to  the  ends  of 
cords,  by  which  they  were  afterward  withdrawn,  the  fluids  which 
they  had  absorbed  being  then  expressed  and  examined. 

The  first  decisive  experiments  on  this  point,  however,  were  those  » 
performed  by  Dr.  Beaumont,  of  the  U,  S.  Army,  on  the  person  of 
Alexis  St.  Martin,  a  Canadian  boatman,  who  had  a  permanent  gas- 
tric fistula,  the  result  of  an  accidental  gunshot  wound.  The  musket, 
which  was  loaded  with  buckshot  at  the  time  of  the  accident,  was 
discharged,  at  the  distance  of  a  few  feet  from  St.  Martin's  body,  in 
such  a  manner  as  to  tear  away  the  integument  at  the  lower  part  of 
the  left  chest,  open  the  pleural  cavity,  and  penetrate,  through  the 


136  DIGESTION. 

lateral  portion  of  tlie  diaphragm,  into  the  great  pouch,  of  the  stomach. 
After  the  integument  and  the  pleural  and  peritoneal  surfaces  had 
united  and  cicatrized,  there  remained  a  permanent  opening,  of  about 
four-fifths  of  an  inch  in  diameter,  leading  into  the  left  extremity  of 
the  stomach,  which  was  usually  closed  by  a  circular  valve  of  pro- 
truding mucous  membrane.  This  valve  could  be  readily  depressed 
at  any  time,  so  as  to  open  the  fistula  and  allow  the  contents  of  the 
stomach  to  be  extracted  for  examination. 

Dr.  Beaumont  experimented  upon  this  person  at  various  intervals 
from  the  year  1825  to  1832.'  He  established  during  the  course  of 
his  examinations  the  following  important  facts :  First,  that  the  ac- 
tive agent  in  digestion  is  an  acid  fluid,  secreted  by  the  walls  of  the 
stomach  ;  secondly,  that  this  fluid  is  poured  out  by  the  glandular 
walls  of  the  organ  only  during  digestion,  and  under  the  stimulus  of 
the  food ;  and  finally,  that  it  will  exert  its  solvent  action  upon  the 
food  outside  the  body  as  well  as  in  the  stomach,  if  kept  in  glass 
phials  upon  a  sand  bath  at  the  temperature  of  100°  F.  He  made 
also  a  variety  of  other  interesting  investigations  as  to  the  effect 
of  various  kinds  of  stimulus  on  the  secretion  of  the  stomach,  the 
rapidity  with  which  the  process  of  digestion  takes  place,  the  com- 
parative digestibility  of  various  kinds  of  food,  &c.  &c. 

Since  Dr.  Beaumont's  time  it  has  been  ascertained  that  similar 
gastric  fistulse  may  be  produced  at  will  on  some  of  the  lower  animals 
by  a  simple  operation ;  and  the  gastric  juice  has  in  this  way  been 
obtained,  usually  from  the  dog,  by  BlondloL,  Schwann,  Bernard, 
Lehmann  and  others.  The  simplest  and  most  expeditious  mode 
of  doing  the  operation  is  the  best.  An  incision  should  be  made 
G'hrough  the  abdominal  parietes  in  the  median  line,  over  the  great 
curvature  of  the  stomach.  The  anterior  wall  of  the  organ  is  then 
to  be  seized  with  a  pair  of  hooked  forceps,  drawn  out  at  the  external 
wound,  and  opened  with  the  point  of  a  bistoury.  A  short  silver 
canula,  one-half  to  three-quarters  of  an  inch  in  diameter,  armed  at 
each  extremity  with  a  narrow  projecting  rim  or  flange,  is  then  in- 
serted into  the  wound  in  the  stomach,  the  edges  of  which  are  fast- 
ened round  the  tube  with  a  ligature  in  order  to  prevent  the  escape 
of  the  gastric  fluids  into  the  peritoneal  cavity.  The  stomach  is  then 
returned  to  its  place  in  the  abdomen,  and  the  canula  allowed  to  re- 
main with  its  external  flange  resting  upon  the  edges  of  the  wound 
in  the  abdominal  integuments,  which  are  to  be  drawn  together  by 

'  Experiments  and  Observations  i:pon  the  Gastric  Juice.     Boston,  1834. 


GASTKIC    JUICE,    AND    STOMACH    DIGESTION.  137 

sutures.  The  animal  may  be  kept  perfectly  quiet,  during  the  ope- 
ration, by  the  administration  of  ether  or  chloroform.  In  a  few 
days  the  ligatures  come  away,  the  wounded  peritoneal  surfaces  are 
united  with  each  other,  and  the  canula  is  retained  in  a  permanent 
gastric  fistula ;  being  prevented  by  its  flaring  extremities  both  from 
falling  out  of  the  abdomen  and  from  being  accidentally  pushed  into 
the  stomach.  It  is  closed  externally  by  a  cork,  which  may  be  with- 
drawn at  pleasure,  and  the  contents  of  the  stomach  withdrawn  for 
examination. 

Experiments  conducted  in  this  manner  confirm,  in  the  main,  the 
results  obtained  by  Dr.  Beaumont.  Observations  of  this  kind  are 
in  some  respects,  indeed,  more  satisfactory  when  made  upon  the 
lower  animals,  than  upon  the  human  subject ;  since  animals  are 
entirely  under  the  control  of  the  experimenter,  and  all  sources  of 
deception  or  mistake  are  avoided,  while  the  investigation  is,  at  the 
same  time,  greatly  facilitated  by  the  simple  character  of  their  food. 

The  gastric  juice,  like  the  saliva,  is  secreted  in  considerable 
quantity  only  under  the  stimulus  of  recently  ingested  food.  Dr. 
Beaumont  states  that  it  is  entirely  absent  during  the  intervals  of 
digestion ;  and  that  the  stomach  at  that  time  contains  no  acid  fluid, 
but  only  a  little  neutral  or  alkaline  mucus.  He  was  able  to  obtain 
a  suf&cient  quantity  of  gastric  juice  for  examination,  by  gently  irri- 
tating the  mucous  membrane  with  a  gum-elastic  catheter,  or  the  end 
of  a  glass  rod,  and  by  collecting  the  secretion  as  it  ran  in  drops 
from  the  fistula.  On  the  introduction  of  food,  he  found  that  the 
mucous  membrane  became  turgid  and  reddened,  a  clear  acid  fluid 
collected  everywhere  in  drops  underneath  the  layer  of  mucus  lin- 
ing the  walls  of  the  stomach,  and  was  soon  poured  out  abundantly 
into  its  cavity.  "We  have  found,  however,  that  the  rule  laid  down 
by  Dr.  Beaumont  in  this  respect,  though  correct  in  the  main,  is  not 
invariable.  The  truth  is,  the  irritability  of  the  gastric  mucous 
membrane,  and  the  readiness  with  which  the  flow  of  gastric  juice 
may  be  excited,  varies  considerably  in  different  animals ;  even  in 
those  belonging  to  the  same  species.  In  experimenting  with  gastric 
fistulte  on  different  dogs,  for  example,  we  have  found  in  one  instance, 
like  Dr.  Beaumont,  that  the  gastric  juice  was  always  entirely  absent 
in  the  intervals  of  digestion ;  the  mucous  membrane  then  present- 
ing invariably  either  a  neutral  or  slightly  alkaline  reaction.  In 
this  animal,  which  was  a  perfectly  healthy  one,  the  secretion  could 
not  be  excited  by  any  artificial  means,  such  as  glass  rods,  metallic 
catheters,  and  the  like;  but  only  by  the  natural  stimulus  of  ingested 


138  DIGESTION. 

food..  We  have  even  seen  tougli  and  indigestible  pieces  of  tendon, 
introduced  througli  tlie  fistula,  expelled  again  in  a  few  minutes,  one 
after  the  other,  without  exciting  the  flow  of  a  single  drop  of  acid 
fluid ;  while  pieces  of  fresh  meat,  introduced  in  the  same  way,  pro- 
duced at  once  an  abundant  supply.  In  other  instances,  on  the  con- 
trary, the  introduction  of  metallic  catheters,  &c.,  into  the  empty 
stomach  has  produced  a  scanty  flow  of  gastric  juice;  and  in  experi- 
menting upon  dogs  that  have  been  kept  without  food  during  various 
periods  of  time  and  then  killed  by  section  of  the  medulla  oblongata, 
we  have  usually,  though  not  always,  found  the  gastric  mucous  mem- 
brane to  present  a  distinctly  acid  reaction,  even  after  an  abstinence 
of  six,  seven,  or  eight  days.  There  is  at  no  time,  however,  under 
these  circumstances,  any  considerable  amount  of  fluid  present  in 
the  stomach ;  but  only  just  sufficient  to  moisten  the  gastric  mucous 
membrane,  and  give  it  an  acid  reaction. 

The  gastric  juice,  which  is  obtained  by  irritating  the  stomach 
with  a  metallic  catheter,  is  clear,  perfectly  colorless,  and  acid  in 
reaction.  A  sufficient  quantity  of  it  cannot  be  obtained  by  this 
method  for  any  extended  experiments ;  and  for  that  purpose,  the 
animal  should  be  fed,  after  a  fast  of  twenty-four  hours,  with  fresh 
lean  meat,  a  little  hardened  by  short  boiling,  in  order  to  coagulate 
the  fluids  of  the  muscular  tissue,  and  prevent  their  mixing  with  the 
gastric  secretion.  No  effect  is  usually  apparent  within  the  first  five 
minutes  after  the  introduction  of  the  food.  At  the  end  of  that  time 
the  gastric  juice  begins  to  flow ;  at  first  slowly,  and  in  drops.  It  is 
then  perfectly  colorless,  but  very  soon  acquires  a  slight  amber 
tinge.  It  then  begins  to  flow  more  freely,  usually  in  drops,  but 
often  running  for  a  few  seconds  in  a  continuous  stream.  In  this 
way  from  5ij  to  liiss  may  be  collected  in  the  course  of  fifteen 
minutes.  Afterward  it  becomes  somewhat  turbid  with  the  debris 
of  the  food,  which  has  begun  to  be  disintegrated ;  but  from  this  it 
may  be  readily  separated  by  filtration.  After  three  hours,  it  con- 
tinues to  run  freely,  but  has  become  very  much  thickened,  and 
even  grumous  in  consistency,  from  the  abundant  admixture  of 
alimentary  debris.  In  six  hours  after  the  commencement  of  diges- 
tion it  runs  less  freely,  and  in  eight  hours  has  become  very  scanty, 
though  it  continues  to  preserve  the  same  physical  appearances  as 
before.  It  ceases  to  flow  altogether  in  from  nine  to  twelve  hours, 
according  to  the  quantity  of  food  taken. 

For  purposes  of  examination,  the  fluid  drawn  during  the  first 
fifteen  minutes  after  feeding  should  be  collected,  and  separated  by 


GASTRIC    JUICE;   AND    STOMACH    DIGESTION.  139 

filtration  from  accidental  impurities.  Obtained  in  this  way,  tlie 
gastric  juice  is  a  clear,  watery  fluid,  without  any  appreciable  vis- 
cidity, very  distinctly  acid  to  test  paper,  of  a  faint  amber  color, 
and  with  a  specific  gravity  of  1010.  It  becomes  opalescent  on 
boiling,  owing  to  the  coagulation  of  its  organic  ingredients.  The 
following  is  the  composition  of  the  gastric  juice  of  the  dog,  based 
on  a  comparison  of  various  analyses  by  Lehmann,  and  Bidder  and 
Schmidt : — 

Composition  of  Gastric  Jpice. 

Water 975.00 

Organic  matter         .........  15.00 

Lactic  acid       ..........  4.78 

Cliloride  of  sodium           ........  1.70 

"         "  potassium 1.08 

"          "  calcium 0.20 

"          "  ammonium     ........  0.65 

Phosphate  of  lime 1.48 

"           "   magnesia 0.06 

"           "    iron 0.05 

1000.00 

In  place  of  lactic  acid.  Bidder  and  Schmidt  found,  in  most  of  their 
analyses,  hydrochloric  acid.  Lehmann  admits  that  a  small  quantity 
of  hydrochloric  acid  is  sometimes  present,  but  regards  lactic  acid 
as  much  the  most  abundant  and  important  of  the  two.  Eobin  and 
Yerdeil  also  regard  the  acid  reaction  of  the  gastric  juice  as  due  to 
lactic  acid;  and,  finally,  Bernard  has  shown,^  by  a  series  of  well 
contrived  experiments,  that  the  free  acid  of  the  dog's  gastric  juice 
is  undoubtedly  the  lactic ;  and  that  the  hydrochloric  acid  obtained 
by  distillation  is  really  produced  by  a  decomposition  of  the  chlo- 
rides, which  enter  into  the  composition  of  the  fresh  juice. 

The  free  acid  is  an  extremely  important  ingredient  of  the  gastric 
secretion,  and  is,  in  fact,  essential  to  its  physiological  properties ; 
for  the  gastric  juice  will  not  exert  its  solvent  action  upon  the  food, 
after  it  has  been  neutralized  by  the  addition  of  an  alkali  or  an 
alkaline  carbonate. 

The  most  important  ingredient  of  the  gastric  juice,  beside  the 
free  acid,  is  its  organic  matter  or  "  ferment,"  which  is  sometimes 
known  under  the  name  oi  jjepsine.  This  name,  "pepsine,"  was 
originally  given  by  Schwann  to  a  substance  which  he  obtained 
from  the  mucous  membrane  of  the  pig's  stomach,  by  macerating  it 
in  distilled  water  until  a  putrid  odor  began  to  be  developed.     The 

»  Lemons  de  Physiologie  Experimentale,  Paris,  1856,  p.  396. 


140 


DIGESTION. 


substance  in  question  was  precipitated  from  the  watery  infusion  by 
the  addition  of  alcohol,  and  dried ;  and  if  dissolved  afterward  in 
acidulated  water,  it  was  found  to  exert  a  solvent  action  on  boiled 
white  of  egg.  This  substance,  however,  did  not  represent  precisely 
the  natural  ingredient  of  the  gastric  secretion,  and  was  probably  a 
mixture  of  various  matters,  some  of  them  the  products  of  com- 
mencing decomposition  of  the  mucous  membrane  itself.  The  name 
pepsine,  if  it  be  used  at  all,  should  be  applied  to  the  organic  matter 
which  naturally  occurs  in  solution  in  the  gastric  juice.  It  is  alto- 
gether unessential,  in  this  respect,  from  what  source  it  may  be 
originally  derived.  It  has  been  regarded  by  Bernard  and  others, 
on  somewhat  insufficient  grounds,  as  a  product  of  the  alteration  of 
the  mucus  of  the  stomach.  But  whatever  be  its  source,  since  it  is 
always  present  in  the  secretion  of  the  stomach,  and  takes  an  active 
part  in  the  performance  of  its  function,  it  can  be  regarded  in  no 
other  light  than  as  a  real  anatomical  ingredient  of  the  gastric  juice, 
and  as  essential  to  its  constitution. 

Pepsine  is  precipitated  from  its  solution  in  the  gastric  juice  by 
absolute  alcohol,  and  by  various  metallic  salts,  but  is  not  affected 

by  ferrocyanide  of  potassium. 
Fig.  30.  It   is  precipitated   also,  and 

coagulated,  by  a  boiling  tem- 
perature; and  the  gastric 
juice,  accordingly,  after  being 
boiled,  becomes  turbid,  and 
loses  altogether  its  power  of 
dissolving  alimentary  sub- 
stances. Gastric  juice  is  also 
affected  in  a  remarkable 
manner  by  being  mingled 
with  bile.  We  have  found 
that  four  to  six  drops  of  dog's 
bile  precipitate  completely 
with  3j  of  gastric  juice  from 
the  same  animal ;  so  that  the 
whole  of  the  biliary  coloring 
matter  is  thrown  down  as  a 
deposit,  and  the  filtered  fluid  is  found  to  have  lost  entirely  its 
digestive  power,  though  it  retains  an  acid  reaction. 

A  very  singular  property  of  the  gastric  juice  is  its  inaptitude  for 
'putrefaction.     It  may  be  kept  for  an  indefinite  length  of  time  in  a 


CoNFEBvoiD  Vegetable,  growing  in  the  Gas- 
tric Juice  of  the  Dog.  Tlie  fibres  have  an  average 
diameter  of  1-7000  of  an  inch. 


GASTRIC    JUICE,   AND    STOMACH    DIGESTION.  141 

common  glass-stoppered  bottle  without  developing  any  putrescent 
odor.  A  light  deposit  generally  collects  at  the  bottom,  and  a  con- 
fervoid  vegetable  growth  or  "mould"  often  shows  itself  in  the  fluid 
after  it  has  been  kept  for  one  or  two  weeks.  This  growth  has  the 
form  of  white,  globular  masses,  each  of  which  is  composed  of  deli- 
cate radiating  branched  filaments  (Fig.  30) ;  each  filament  consisting 
of  a  row  of  elongated  cells,  like  other  vegetable  growths  of  a  similar 
nature.  These  growths,  however,  are  not  accompapied  by  any 
putrefactive  changes,  and  the  gastric  juice  retains  its  acid  reaction 
and  its  digestive  properties  for  many  months. 

By  experimenting  artificially  with  gastric  juice  on  various  ali- 
mentary substances,  such  as  meat,  boiled  white  of  egg,  &c.,  it  is 
found,  as  Dr.  Beaumont  formerly  observed,  to  exert  a  solvent  action 
on  these  substances  outside  the  body,  as  well  as  in  the  cavity  of  the 
stomach.  This  action  is  most  energetic  at  the  temperature  of  100° 
F.  It  gradually  diminishes  in  intensity  below  that  point,  and  ceases 
altogether  near  32°.  If  the  temperature  be  elevated  above  100° 
the  action  also  becomes  enfeebled,  and  is  entirely  suspended  about 
160°,  or  the  temperature  of  coagulating  albumen.  Contrary  to 
what  was  supposed,  however,  by  Dr.  Beaumont,  and  his  predeces- 
sors, the  gastric  juice  is  not  a  universal  solvent  for  all  alimentary 
substances,  but,  on  the  contrary,  affects  only  a  single  class  of  the 
proximate  principles,  viz.,  the  albuminoid  or  organic  substances. 
Neither  starch  nor  oil,  when  digested  in  it  at  the  temperature  of 
the  body,  suffers  the  slightest  chemical  alteration.  Fatty  matters 
are  simply  melted  by  the  heat,  and  starchy  substances  are  only 
hydrated  and  gelatinized  to  a  certain  extent  by  the  combined  influ- 
ence of  the  warmth  and  moisture.  Solid  and  semi-solid  albuminoid 
matters,  however,  are  at  once  attacked  and  liquefied  by  the  diges- 
tive fluid.  Pieces  of  coagulated  white  of  egg  suspended  in  it,  in  a 
test-tube,  are  gradually  softened  on  their  exterior,  and  their  edges 
become  pale  and  rounded.  They  grow  thin  and  transparent; 
and  their  substance  finally  melts  away,  leaving  a  light  scanty  de- 
posit, which  collects  at  the  bottom  of  the  test-tube.  While  the 
disintegrating  process  is  going  on,  it  may  almost  always  be  noticed 
that  minute,  opaque  spots  show  themselves  in  the  substance  of  the 
liquefying  albumen,  indicating  that  certain  parts  of  it  are  less  easily 
attacked  than  the  rest ;  and  the  deposit  which  remains  at  the  bot- 
tom is  probably  also  composed  of  some  ingredient,  not  soluble  in 
the  gastric  juice.  If  pieces  of  fresh  meat  be  treated  in  the  same 
manner,  the  areolar  tissue    entering    into  its  composition  is  first 


142  DIGESTION. 

dissolved,  so  tliat  tlie  muscular  bundles  become  more  distinct,  and 
separate  from  eacli  other.  They  gradually  fall  apart,  and  a  little 
brownish  deposit  is  at  last  all  that  remains  at  the  bottom  of  the 
tube.  If  the  hard  adipose  tissue  of  beef  or  mutton  be  subjected 
to  the  same  process,  the  walls  of  the  fat  vesicles  and  the  inter- 
vening areolar  tissue,  together  with  the  capillary  bloodvessels,  &c., 
are  dissolved ;  while  the  oily  matters  are  set  free  from  their  en- 
velops, and  collect  in  a  white,  opaque  layer  on  the  surface.  In 
cheese,  the  casein  is  dissolved,  and  the  oil  which  it  contains  set 
free.  In  bread  the  gluten  is  digested,  and  the  starch  left  un- 
changed. In  milk,  the  casein  is  first  coagulated  by  contact  with 
the  acid  gastric  fluids,  and  afterward  slowly  liquefied,  like  other 
albuminoid  substances. 

The  time  required  for  the  complete  liquefaction  of  these  sub- 
stances varies  with  the  quantity  of  matter  present,  and  with  its  state 
of  cohesion.  The  process  is  hastened  by  occasionally  shaking  up 
the  mixture,  so  as  to  separate  the  parts  already  disintegrated,  and 
bring  the  gastric  fluid  into  contact  with  fresh  portions  of  the  diges- 
tible substance. 

The  liquefying  process  which  the  food  undergoes  in  the  gastric 
juice  is  not  a  simple  solution.  It  is  a  catalytic  transformation, 
produced  in  the  albuminoid  substances  by  contact  with  the  organic 
matter  of  the  digestive  fluid.  This  organic  matter  acts  in  a  similar 
manner  to  that  of  the  catalytic  bodies,  or  "ferments,"  generally. 
Its  peculiarity  is  that,  for  its  active  operation,  it  requires  to  be  dis- 
solved in  an  acidulated  fluid.  In  common  with  other  ferments,  it 
requires  also  a  moderate  degree  of  warmth ;  its  action  being  checked, 
both  by  a  very  low,  and  a  very  high  temperature.  By  its  opera- 
tion the  albuminoid  matters  of  the  food,  whatever  may  have  been 
their  original  character,  are  all,  without  distinction,  converted  into 
a  new  substance,  viz.,  alhuminose.  This  substance  has  the  general 
characters  belonging  to  the  class  of  organic  matters.  It  is  uncrys- 
tallizable,  and  contains  nitrogen  as  an  ultimate  element.  It  is  pre- 
cipitated, like  albumen,  by  an  excess  of  alcohol,  and  by  the  metallic 
salts ;  but  unlike  albumen,  is  not  affected  by  nitric  acid  or  a  boil- 
ing temperature.  It  is  freely  soluble  in  water,  and  after  it  is  once 
produced  by  the  digestive  process,  remains  in  a  fluid  condition, 
and  is  ready  to  be  absorbed  by  the  vessels.  In  this  way,  casein, 
fibrin,  musculine,  gluten,  &c.,  are  all  reduced  to  the  condition  of 
alburninose.  By  experimenting  as  above,  with  a  mixture  of  food 
and  gastric  juice  in  test-tubes,  we  have  found  that  the  casein  of 


GASTRIC    JUICE,    AND    STOMACH    DIGESTION.  143 

cheese  is  entirely  converted  into  albuminose,  and  dissolved  under 
that  form,  A  very  considerable  portion  of  raw  white  of  egg,  how- 
ever, dissolves  in  the  gastric  juice  directly  as  albumen,  and  retains 
its  property  of  coagulating  by  heat.  Soft-boiled  white  of  egg  and 
raw  meat  are  principally  converted  into  albuminose ;  but  at  the 
same  time,  a  small  portion  of  albumen  is  also  taken  up  unchanged. 

The  above  process  is  a  true  liquefaction  of  the  albuminoid  sub- 
stances, and  not  a  simple  disintegration.  If  fresh  meat  be  cut  into 
small  pieces,  and  artificially  digested  in  gastric  juice  in  test-tubes, 
at  100°  F.,  and  the  process  assisted  by  occasional  gentle  agitation, 
the  fluid  continues  to  take  up  more  and  more  of  the  digestible 
material  for  from  eight  to  ten  hours.  At  the  end  of  that  time  if  it 
be  separated  and  filtered,  the  filtered  fluid  has  a  distinct,  brownish 
color,  and  is  saturated  with  dissolved  animal  matter.  Its  specific 
gravity  is  found  to  have  increased  from  1010  to  1020 ;  and  on  the 
addition  of  alcohol  it  becomes  turbid,  with  a  very  abundant  whitish 
precipitate  (albuminose).  There  is  also  a  peculiar  odor  developed 
during  this  process,  which  resembles  that  produced  in  the  malting 
of  barley. 

Albuminose,  in  solution  in  gastric  juice,  has  several  peculiar 
properties.  One  of  the  most  remarkable  of  these  is  that  it  inter- 
feres with  the  operation  of  Trommer's  test  for  grape  sugar  (see 
page  84).  We  first  observed  and  described  this  peculiarity  in 
1854,'  but  could  not  determine,  at  that  time,  upon  what  particular 
ingredient  of  the  gastric  juice  it  depended.  A  short  time  subse- 
quently it  was  also  noticed  by  M.  Longet,  in  Paris,  who  published 
his  observations  in  the  Gazette  Kehdomadaire  for  February  9th, 
1855.'  He  attributed  the  reaction  not  to  the  gastric  juice  itself, 
but  to  the  albuminose  held  in  solution  by  it.  We  have  since  found 
this  explanation  to  be  correct.  Grastric  juice  obtained  from  the 
empty  stomach  of  the  fasting  animal,  by  irritation  with  a  metallic 
catheter,  which  is  clear  and  perfectly  colorless,  does  not  interfere 
in  any  way  with  Trommer's  test ;  but  if  it  be  macerated  for  some 
hours  in  a  test-tube  with  finely  chopped  meat,  at  a  temperature  of 
100°,  it  will  then  be  found  to  have  acquired  the  property  in  a 
marked  degree.  The  reaction  therefore  depends  undoubtedly  upon 
the  presence  of  albuminose  in  solution.  As  the  gastric  juice,  drawn 
from  the  dog's  stomach  half  an  hour  or  more  after  the  introduction 

'  American  Journ.  Med.  Sci.,  Oct.  1854,  p.  319. 

2  Nouvelles  recherches  relatives  it  Paction  du  sue  gastrique  sur  lea  substances 
albuminoides. —  Gaz.  Ilehd.  9  F'Vrier,  1855,  p.  103. 


144  DIGESTION. 

of  food,  already  contains  some  albuminose  in  solution,  it  presents 
tlie  same  reaction.  If  such  gastric  juice  be  mixed  with  a  small 
quantity  of  glucose,  and  Trommer's  test  applied,  no  peculiarity  is 
observed  on  first  dropping  in  the  sulphate  of  copper ;  but  on  adding 
afterward  the  solution  of  potassa,  the  mixture  takes  a  rich  purple  hue, 
instead  of  the  clear  blue  tinge  which  is  presented  under  ordinary 
circumstances.  On  boiling,  the  color  changes  to  claret,  cherry  red, 
and  finally  to  a  light  yellow ;  but  no  oxide  of  copper  is  deposited,  and 
the  fluid  remains  clear.  If  the  albuminose  be  present  only  in  small 
quantity,  an  incomplete  reduction  of  the  copper  takes  place,  so  that 
the  mixture  becomes  opaline  and  cloudy,  but  still  without  any  well 
marked  deposit.  This  interference  will  take  place  when  sugar  is 
present  in  very  large  proportion.  We  have  found  that  in  a  mix- 
ture of  honey  and  gastric  juice  in  equal  volumes,  no  reduction  of 
copper  takes  place  on  the  application  of  Trommer's  test.  It  is 
remarkable,  however,  that  if  such  a  mixture  be  previously  diluted 
with  an  equal  quantity  of  water,  the  interference  does  not  take 
place,  and  the  copper  is  deposited  as  usual. 

Usually  this  peculiar  reaction,  now  that  we  are  acquainted  with 
its  existence,  will  not  practically  prevent  the  detection  of  sugar, 
when  present ;  since  the  presence  of  the  sugar  is  distinctly  indi- 
cated by  the  change  of  color,  as  above  mentioned,  from  purple  to 
yellow,  though  the  copper  may  not  be  thrown  down  as  a  precipi- 
tate. All  possibility  of  error,  furthermore,  may  be  avoided  by 
adopting  the  following  precautions.  The  purple  color,  already  men- 
tioned, will,  in  the  first  place,  serve  to  indicate  the  presence  of  the 
albuminoid  ingredient  in  the  suspected  fluid.  The  mixture  should 
then  be  evaporated  to  dryness,  and  extracted  with  alcohol,  in  order 
to  eliminate  the  animal  matters.  After  that,  a  watery  solution  of 
the  sugar  contained  in  the  alcoholic  extract  will  react  as  usual  with 
Trommer's  test,  and  reduce  the  oxide  of  copper  without  difficulty. 

Another  remarkable  property  of  gastric  juice  containing  albu- 
minose, which  is  not,  however,  peculiar  to  it,  but  common  to  many 
other  animal  fluids,  is  that  of  interfering  with  the  mutual  reaction 
of  starch  and  iodine.  If  5j  of  such  gastric  juice  be  mixed  with  5j 
of  iodine  water,  and  boiled  starch  be  subsequently  added,  no  blue 
color  is  produced ;  though  if  a  larger  quantity  of  iodine  water  be 
a^dded,  or  if  the  tincture  be  used  instead  of  the  aqueous  solution, 
the  superabundant  iodine  then  combines  with  the  starch,  and  pro- 
duces the  ordinary  blue  color.  This  property,  like  that  described 
above,  is  not  possessed  by  pure,  colorless,  gastric  juice,  taken  from 


GASTRIC    JUICE,    AND    STOMACH    DIGESTION.  145 

tlie  empty  stomacli,  but  is  acquired  by  it  on  being  digested  witli 
albuminoid  substances. 

Another  important  action  wbicb  takes  place  in  tbe  stomacli, 
beside  the  secretion  of  the  gastric  juice,  is  the  peristaltic  moveraent 
of  the  organ.  This  movement  is  accomplished  by  the  alternate 
contraction  and  relaxation  of  the  longitudinal  and  circular  fibres 
of  its  muscular  coat.  The  motion  is  minutely  described  by  Dr. 
Beaumont,  who  examined  it,  both  by  watching  the  movements  of 
the  food  through  the  gastric  fistula,  and  also  by  introducing  into 
the  stomach  the  bulb  and  stem  of  a  thermometer.  According  to 
his  observations,  when  the  food  first  passes  into  the  stomach,  and 
the  secretion  of  the  gastric  juice  commences,  the  muscular  coat, 
which  was  before  quiescent,  is  excited  and  begins  to  contract  act- 
ively. The  contraction  takes  place  in  such  a  manner  that  the  food, 
after  entering  the  cardiac  orifice  of  the  stomach,  is  first  carried  to 
the  left,  into  the  great  pouch  of  the  organ,  thence  downward  and 
along  the  great  curvature  to  the  pyloric  portion.  At  a  short  distance 
from  the  pylorus,  Dr.  B.  often  found  a  circular  constriction  of  the 
gastric  parietes,  by  which  the  bulb  of  the  thermometer  was  gently 
grasped  and  drawn  toward  the  pylorus,  at  the  same  time  giving  a 
twisting  motion  to  the  stem  of  the  instrument,  by  which  it  was 
rotated  in  his  fingers.  In  a  moment  or  two,  however,  this  constric- 
tion was  relaxed,  and  the  bulb  of  the  thermometer  again  released, 
and  carried  together  with  the  food  along  the  small  curvature  of 
the  organ  to  its  cardiac  extremity.  This  circuit  was  repeated  so 
long  as  any  food  remained  in  the  stomach ;  but,  as  the  liquefied 
portions  were  successively  removed  toward  the  end  of  digestion,  it 
became  less  active,  and  at  last  ceased  altogether  when  the  stomach 
had  become  completely  empty,  and  the  organ  returned  to  its  ordi- 
nary quiescent  condition. 

It  is  easy  to  observe  the  muscular  action  of  the  stomach  during 
digestion  in  the  dog,  by  the  assistance  of  a  gastric  fistula,  artificially 
established.  If  a  metallic  catheter  be  introduced  through  the  fistula 
when  the  stomach  is  empty,  it  must  usually  be  held  carefully  in 
place,  or  it  will  fall  out  by  its  own  weight.  But  immediately  upon 
the  introduction  of  food,  it  can  be  felt  that  the  catheter  is  grasped 
and  retained  with  some  force,  by  the  contraction  of  the  muscular 
coat.  A  twisting  or  rotatory  motion  of  its  extremity  may  also  be 
frequently  observed,  similar  to  that  described  by  Dr.  Beaumont. 
This  peristaltic  action  of  the  stomach,  however,  is  a  gentle  one, 
and  not  at  all  active  or  violent  in  character.  We  have  never  seen, 
10 


146  DIGESTIOX. 

in  opening  the  abdomen,  any  sucli  energetic  or  extensive  contrac 
tions  of  the  stomacli,  even  when  full  of  food,  as  may  be  easily 
excited  in  the  small  intestine  by  the  mere  contact  of  the  atmosphere, 
or  by  pinching  them  with  the  blades  of  a  forceps.  This  action  of 
the  stomach,  nevertheless,  though  quite  gentle,  is  sufficient  to  pro- 
duce a  constant  churning  movement  of  the  masticated  food,  by 
which  it  is  carried  back  and  forward  to  every  part  of  the  stomach, 
and  rapidly  incorporated  with  the  gastric  juice  which  is  at  the 
same  time  poured  out  by  the  mucous  membrane;  so  that  the 
digestive  fluid  is  made  to  penetrate  equally  every  part  of  the  ali- 
mentary mass,  and  the  digestion  of  all  its  albuminous  ingredients 
goes  on  simultaneously.  This  gentle  and  continuous  movement  of 
the  stomach  is  one  which  cannot  be  successfully  imitated  in  experi- 
ments on  artificial  digestion  with  gastric  juice  in  test-tubes ;  and 
consequently  the  process,  under  these  circumstances,  is  never  so 
rapid  or  so  complete  as  when  it  takes  place  in  the  interior  of  the 
stomach. 

The  length  of  time  which  is  required  for  digestion  varies  in 
different  species  of  animals.  In  the  carnivora,  a  moderate  meal  of 
fresh  uncooked  meat  requires  from  nine  to  twelve  hours  for  its 
complete  solution  and  disappearance  from  the  stomach.  According 
to  Dr.  Beaumont,  the  average  time  required  for  digestion  in  the 
human  subject  is  considerably  less ;  varying  from  one  hour  to  five 
hours  and  a  half,  according  to  the  kind  of  food  employed.  This 
is  probably  owing  to  the  more  complete  mastication  of  the  food 
which  takes  place  in  man,  than  in  the  carnivorous  animals.  By 
examining  the  contents  of  the  stomach  at  various  intervals  after 
feeding,  Dr.  Beaumont  made  out  a  list,  showing  the  comparative 
digestibility  of  different  articles  of  food,  of  which  the  following  are 
the  most  important : — 

Time  required  for  digestion,  according  to  Dr.  Beaumont : — 

Kind  of  Food.  Houks.  Minutes. 

Pig's  feet 1  00 

Tripe 1  00 

Trout  (broiled) 1  30 

Venison  steak     ........  1  35 

Milk '       .         .  2  00 

Roasted  turkey    ........  2  30 

"        beef        ........  8  00 

"        mutton 3  15 

Veal  (broiled) 4  00 

Salt  beef  (boiled) 4  15 

Roasted  pork       ........  5  15 


GASTKTC    JUrCE,   AND    STOMACH    DIGESTION.  147 

Tlie  comparative  digestibility  of  different  substances  varies  more 
or  less  in  different  individuals  according  to  temperament ;  but  the 
above  list  undoubtedly  gives  a  correct  average  estimate  of  the  time 
required  for  stomach  digestion  under  ordinary  conditions. 

A  very  interesting  question  is  that  which  relates  to  the  total 
quantity  of  gastric  juice  secreted  daily.  Whenever  direct  experi- 
ments have  been  performed  with  a  view  of  ascertaining  this  point, 
their  results  have  given  a  considerably  larger  quantity  than  was 
anticipated.  Bidder  and  Schmidt  found  that,  in  a  dog  weighing 
3-i  pounds,  they  were  able  to  obtain  by  separate  experiments,  con- 
suming in  all  12  hours,  one  pound  and  three-quarters  of  gastric 
juice.  The  total  quantity,  therefore,  for  24  hours,  in  the  same  ani- 
mal, would  be  3 1  pounds ;  and,  by  applying  the  same  calculation  to 
a  man  of  medium  size,  the  authors  estimate  the  total  daily  quantity 
in  the  human  subject  as  but  little  less  than  14  pounds  (av.).  This 
estimate  is  probably  not  an  exaggerated  one.  In  order  to  deter- 
mine the  question,  however,  if  possible,  in  a  different  way,  we 
adopted  the  following  plan  of  experiment  with  the  gastric  juice  of 
the  dog.  It  was  first  ascertained,  by  direct  experiment,  that  the 
fresh  lean  meat  of  the  bullock's  heart  loses,  by  complete  desiccation, 
78  per  cent,  of  its  weight,  800  grains  of  such  meat,  cut  into  small 
pieces,  were  then  digested  for  ten  hours,  in  §iss  of  gastric  juice  at 
100°  F.;  the  mixture  being  thoroughly  agitated  as  often  as  every 
hour,  in  order  to  insure  the  digestion  of  as  large  a  quantity  of  meat 
as  possible.  The  meat  remaining  undissolved  was  then  collected 
on  a  previously  weighed  filter,  and  evaporated  to  dryness.  The 
dry  residue  weighed  55  grains.  This  represented,  allowing  for  the 
loss  by  evaporation,  250  grains  of  the  meat,  in  its  natural  moist 
condition  ;  50  grains  of  meat  were  then  dissolved  by  Siss  of  gastric 
juice,  or  33^  grains  per  ounce. 

From  these  data  we  can  form  some  idea  of  the  large  quantity  of 
gastric  juice  secreted  in  the  dog  during  the  process  of  digestion. 
One  pound  of  meat  is  only  a  moderate  meal  for  a  medium-sized 
animal ;  and  yet,  to  dissolve  this  quantity,  no  less  than  thirteen  pints 
of  gastric  juice  will  be  necessary.  This  quantity,  or  any  approxi- 
mation to  it,  would  be  altogether  incredible  if  we  did  not  recollect 
that  the  gastric  juice,  as  soon  as  it  has  dissolved  its  quota  of  food, 
is  immediately  reabsorbed,  and  again  enters  the  circulation,  together 
with  the  alimentary  substances  which  it  holds  in  solution.  The 
secretion  and  rcabsorption  of  the  gastric  juice  then  go  on  simulta- 
neously; and  the  fluids  which  the  blood  loses  by  one  process  are 


148  DIGESTION. 

incessantly  restored  to  it  by  the  other.  A  very  large  quantity, 
therefore,  of  the  secretion  may  be  poured  out  during  the  digestion 
of  a  meal,  at  an  expense  to  the  blood,  at  any  one  time,  of  only  two 
or  three  ounces  of  fluid.  The  simplest  investigation  shows  that 
the  gastric  juice  does  not  accumulate  in  the  stomach  in  any  con- 
siderable quantity  during  digestion ;  but  that  it  is  gradually 
secreted  so  long  as  any  food  remains  undissolved,  each  portion,  as 
it  is  digested,  being  disposed  of  by  reabsorption,  together  with  its 
solvent  fluid.  There  is  accordingly,  during  digestion,  a  constant 
circulation  of  the  digestive  fluids  from  the  bloodvessels  to  the  ali- 
mentary canal,  and  from  the  alimentary  canal  back  again  to  the 
bloodvessels. 

That  this  circulation  really  takes  place  is  proved  by  the  fol- 
lowing facts :  First,  if  a  dog  be  killed  some  hours  after  feeding, 
there  is  never  more  than  a  very  small  quantity  of  fluid  found  in 
the  stomach,  just  sufficient  to  smear  over  and  penetrate  the  half 
digested  pieces  of  meat ;  and,  secondly,  in  the  living  animal,  gastric 
juice,  drawn  from  the  fistula  five  or  six  hours  after  digestion  has 
been  going  on,  contains  little  or  no  more  organic  matter  in  sokition 
than  that  extracted  fifteen  to  thirty  minutes  after  the  introduction 
of  food.  It  has  evidently  been  freshly  secreted ;  and,  in  order  to 
obtain  gastric  juice  saturated  with  alimentary  matter,  it  must  be 
artificially  digested  with  food  in  test-tubes,  where  this  constant  ab- 
sorption and  renovation  cannot  take  place. 

An  unnecessary  dif&culty  has  sometimes  been  felt  in  understand- 
ing how  it  is  that  the  gastric  juice,  which  digests  so  readily  all  albu- 
minous substances,  should  not  destroy  the  walls  of  the  stomach 
itself,  which  are  composed  of  similar  materials.  This,  in  fact,  was 
brought  forward  at  an  early  day,  as  an  insuperable  objection  to  the 
doctrine  of  Eeaumur  and  Spallanzani,  that  digestion  was  a  process 
of  chemical  solution  performed  by  a  digestive  fluid.  It  was  said 
to  be  impossible  that  a  fluid  capable  of  dissolving  animal  matters 
should  be  secreted  by  the  walls  of  the  stomach  without  attacking 
them  also,  and  thus  destroying  the  organ  by  which  it  was  itself 
produced.  Since  that  time,  various  complicated  hypotheses  have 
been  framed,  in  order  to  reconcile  these  apparently  contradictory 
facts.  The  true  explanation,  however,  as  we  believe,  lies  in  this — 
that  the  process  of  digestion  is  not  a  simple  solution,  but  a  catalytic 
transformation  of  the  alimentary  substances,  produced  by  contact 
with  the  pepsine  of  the  gastric  juice.  We  know  that  all  the  or- 
ganic substances  in  the  living  tissues  are  constantly  undergoing,  in 


GASTRIC    JUICE,    AND    STOMACH    DIGESTION.  149 

the  process  of  nutrition,  a  series  of  catalytic  clianges,  whicli  are 
characteristic  of  the  vital  operations,  and  which  are  determined  bj 
the  organized  materials  with  which  they  are  in  contact,  and  by  all 
the  other  conditions  present  in  the  living  organism.  These  changes, 
therefore,  of  nutrition,  secretion,  &c.,  necessarily  exclude  for  the 
time  all  other  catalyses,  and  take  precedence  of  them.  In  the  same 
way,  any  dead  organic  matter,  exposed  to  warmth,  air,  and  moist- 
ure, putrefies ;  but  if  immersed  in  gastric  juice,  at  the  same 
temperature,  the  putrefactive  changes  are  stopped  or  altogether 
prevented,  because  the  catalytic  actions,  excited  by  the  gastric 
juice,  take  precedence  of  those  which  constitute  putrefaction.  For 
a  similar  reason  the  organic  ingredient  of  the  gastric  juice,  which 
acts  readily  on  dead  animal  matter,  has  no  effect  on  the  living 
tissues  of  the  stomach,  because  they  are  already  subject  to  other 
catalytic  influences,  which  exclude  those  of  digestion,  as  well  as 
those  of  putrefaction.  As  soon  as  life  departs,  however,  and  the 
peculiar  actions  taking  place  in  the  living  tissues  come  to  an  end 
with  the  stoppage  of  the  circulation,  the  walls  of  the  stomach  are 
really  attacked  by  the  gastric  juice  remaining  in  its  cavity,  and 
are  more  or  less  completely  digested  and  liquefied.  In  the  human 
subject,  it  is  rare  to  make  an  examination  of  the  body  twenty-four 
or  thirty-six  hours  after  death,  without  finding  the  mucous  mem- 
brane of  the  great  pouch  of  the  stomach  more  or  less  softened  and 
disintegrated  from  this  cause.  Sometimes  the  mucous  membrane 
is  altogether  destroyed,  and  the  submucous  cellular  layer  exposed  ; 
and  occasionally,  when  death  has  taken  place  suddenly  during 
active  digestion,  while  the  stomach  contained  an  abundance  of 
gastric  juice,  all  the  coats  of  the  organ  have  been  found  destroyed, 
and  a  perforation  produced  leading  into  the  peritoneal  cavity. 
These  post-mortem  changes  show  that,  after  death,  the  gastric  juice 
really  dissolves  the  coats  of  the  stomach  without  difiiculty.  But 
during  life,  the  chemical  changes  of  nutrition,  which  are  going  on 
in  their  tissues,  protect  them  from  its  influence,  and  effectually 
preserve  their  integrity. 

The  secretion  of  the  gastric  juice  is  much  influenced  by  nervous 
conditions.  It  was  noticed  by  Dr.  Beaumont,  in  his  experiments 
upon  St.  Martin,  that  irritation  of  the  temper,  and  other  moral 
causes,  would  frequently  diminish,  or  altogether  suspend  the  supply 
of  the  gastric  fluids.  Any  febrile  action  in  the  system  or  any 
unusual  fatigue,  was  liable  to  exert  a  similar  effect.  Every  one  is 
aware  how  readily  any  mental  disturbance,  such  as  anxiety,  anger, 


150  DIGESTION. 

or  vexation,  will  take  away  the  appetite  and  interfere  with  diges- 
tion. Any  nervous  impression  of  this  kind,  occurring  at  the  com- 
inencement  of  digestion,  seems  moreover  to  produce  some  change 
which  has  a  lasting  effect  upon  the  process;  for  it  is  very  often 
noticed  that  when  any  annoyance,  hurry,  or  anxiety  occurs  soon 
after  the  food  has  been  taken,  though  it  may  last  only  for  a  few 
moments,  the  digestive  process  is  not  only  liable  to  be  suspended 
for  the  time,  but  to  be  permanently  disturbed  during  the  entire 
day.  In  order  that  digestion,  therefore,  may  go  on  properly  in  the 
stomach,  food  must  be  taken  only  when  the  appetite  demands  it ; 
it  should  also  be  thoroughly  masticated  at  the  outset ;  and,  finally, 
both  mind  and  body,  particularly  during  the  commencement  of  the 
process,  should  be  free  from  any  unusual  or  disagreeable  excite- 
ment. 

Intestinal  Juices,  and  the  Digestion  of  Sugar  and  Staech. 
— From  the  stomach,  those  portions  of  the  food  which  have  not 
already  suffered  digestion  pass  into  the  third  division  of  the  ali- 
mentary canal,  viz.,  the  small  intestine.  As  already  mentioned,  it 
is  only  the  albuminous  matters  which  are  digested  in  the  stomach. 
Cane  sugar,  it  is  true,  is  slowly  converted  by  the  gastric  juice,  out- 
side the  body,  into  glucose.  "We  have  found  that  ten  grains  of 
cane  sugar,  dissolved  in  5ss  of  gastric  juice,  give  traces  of  glucose 
at  the  end  of  two  hours ;  and  in  three  hours,  the  quantity  of  this 
substance  is  considerable.  It  cannot  be  shown,  however,  that  the 
gastric  juice  exerts  this  effect  on  sugar  during  ordinary  digestion. 
If  pure  sugar  cane  be  given  to  a  dog  with  a  gastric  fistula,  while 
digestion  of  meat  is  going  on,  it  disappears  in  from  two  to  three 
hours,  without  any  glucose  being  detected  in  the  fluids  withdrawn 
from  the  stomach.  It  is,  therefore,  either  directly  absorbed  under 
the  form  of  cane  sugar,  or  passes,  little  by  little,  into  the  duodenum, 
where  the  intestinal  fluids  at  once  convert  it  into  glucose. 

It  is  equally  certain  that  starchy  matters  are  not  digested  in  the 
stomach,  but  pass  unchanged  into  the  small  intestine.  Here  they 
meet  with  the  mixed  intestinal  fluids,  which  act  at  once  upon  the 
starch,  and  convert  it  rapidly  into  sugar.  The  intestinal  fluids, 
taken  from  the  duodenum  of  a  recently  killed  dog,  exert  this 
transforming  action  upon  starch  with  the  greatest  promptitude,  if 
mixed  with  it  in  a  test-tube,  and  kept  at  the  temperature  of  100°  F. 
Starch  is  converted  into  sugar  by  this  means  much  more  rapidly 
and  certainly  than  by  the  saliva ;  and  experiment  shows  that  the 


INTESTINAL    JUICES,   DIGESTION    OF    SUGAR,   ETC.       151 


intestinal  fluids  are  the  active  agents  in  its  digestion  during  life. 
If  a  dog  be  fed  with  a  mixture  of  meat  and  boiled  starch,  and  killed 
a  short  time  after  the  meal,  the  stomach  is  found  to  contain  starch 
but  no  sugar ;  while  in  the  small  intestine  there  is  an  abundance  of 
sugar,  and  but  little  or  no  starch.  If  some  observers  have  failed 
to  detect  sugar  in  the  intestine  after  feeding  the  animal  with 
starch,  it  is  because  they  have  delayed  the  examination  until  too 
late.  For  it  is  remarkable  how  rapidly  starchy  substances,  if  pre- 
viously disintegrated  by  boiling,  are  disposed  of  in  the  digestive 
process.  If  a  dog,  for  example,  be  fed  as  above  with  boiled  starch 
and  meat,  while  some  of  the  meat  remains  in  the  stomach  for 
eight,  nine,  or  ten  hours,  the  starch  begins  immediately  to  pass  into 
the  intestine,  where  it  is  at  once  converted  into  sugar,  and  then  as 
rapidly  absorbed.  The  whole  of  the  starch  may  be  converted  into 
sugar,  and  completely  absorbed,  in  an  hour's  time.  We  have  even 
found,  at  the  end  of  three-quarters  of  an  hour,  after  a  tolerably 
full  meal  of  boiled  starch  and  meat,  that  all  trace  of  both  starch 
and  sugar  had  disappeared  from  both  stomach  and  intestine.  The 
rapidity  with  which  this  passage  of  the  starch  into  the  duodenum 
takes  place  varies,  to  some 

extent,  in  difierent  animals,  ^^"  ^^' 

according  to  the  general  ac- 
tivity of  the  digestive  appa- 
ratus; but  it  is  always  a 
comparatively  rapid  process, 
when  the  starch  is  already 
liquefied  and  is  administered 
in  a  pure  form.  There  can 
be  no  doubt  that  the  natural 
place  for  the  digestion  of 
starchy  matters  is  the"  small 
intestine,  and  that  it  is  ac- 
complished by  the  action  of 
the  intestinal  juices. 

Our  knowledge  is  not  very 
complete  with  regard  to  the 
exact  nature  of  the  fluids  by  which  this  digestion  of  the  starch  is 
accomplished.  The  juices  taken  from  the  duodenum  are  generally 
a  mixture  of  three  different  secretions,  viz.,  the  bile,  the  pancreatic 
fluid,  and  the  intestinal  juice  proper.  Of  these,  the  bile  may  be 
left  out  of  the  question ;  since  it  does  not,  when  in  a  pure  state, 


Follicles  of   Liebekkuhn,  from    SraaU    In- 
testine of  dog. 


152 


DIGESTION", 


exert  any  digestive  action  on  starch.  The  pancreatic  juice,  on  the 
other  hand,  has  the  property  of  converting  starch  into  sugar ;  but 
it  is  not  known  whether  this  fluid  be  always  present  in  the  duode- 
num. The  true  intestinal  juice  is  the  product  of  two  sets  of  glan- 
dular organs,  seated  in  the  substance  of  or  beneath  the  mucous 
membrane,  viz.,  the  follicles  of  Lieberkiihn  and  the  glands  of  Brun- 
ner.  The  first  of  these,  or  Lieberkiihn's  follicles  (Fig.  31),  are  the 
most  numerous.  They  are  simple,  nearly  straight  tubules,  lined 
with  a  continuation  of  the  intestinal  epithelium,  and  somewhat 
similar  in  their  appearance  to  the  follicles  of  the  pyloric  portion  of 
the  stomach.  They  occupy  the  whole  thickness  of  the  mucous 
membrane,  and  are  found  in  great  numbers  throughout  the  entire 
length  of  the  small  and  large  intestine. 

The  glands  of  Brunner  (Fig.  32),  or  the  duodenal  glandulae,  as 
they  are  sometimes  called,  are  confined  to  the  upper  part  of  the  duo- 
denum, where  they  exist  as  a 
Fig.  32.  closely  set  layer,  in  the  deeper 

portion  of  the  mucous  mem- 
brane, extending  downward  a 
short  distance  from  the  pylo- 
rus. They  are  composed  of 
a  great  number  of  rounded 
follicles,  clustered  round  a 
central  excretory  duct.  Each 
follicle  consists  of  a  delicate 
membranous  wall,  lined  with 
glandular  epithelium,  and 
covered  on  its  surface  with 
small,  distinctly  marked  nu- 
clei. The  follicles  collected 
around  each  duct  are  bound 
together  by  a  thin  layer  of 
areolar  tissue,  and  covered  with  a  plexus  of  capillary  bloodvessels. 
The  intestinal  juice,  which  is  the  secreted  product  of  the  above 
glandular  organs,  has  been  less  successfully  studied  than  the  other 
digestive  fluids,  owing^  to  the  difficulty  of  obtaining  it  in  a  pure 
state.  The  method  usually  adopted  has  been  to  make  an  opening 
in  the  abdomen  of  the  living  animal,  take  out  a  loop  of  intestine, 
empty  it  by  gentle  pressure,  and  then  to  shut  off"  a  portion  of  it 
from  the  rest  of  the  intestinal  cavity  by  a  couple  of  ligatures, 
situated  six  or  eight  inches  apart ;  after  which  the  loop  is  returned 


Portion     of    one    of    Bk  u  N-viiU's 
Glands,  from  Hamaa  lucestine. 


Duodenal 


PANCKEATIC    JUICE,    AND    THE    DIGESTION"    OF    FAT.      153 

into  the  abdomen,  and  the  external  wound  closed  by  sutures. 
After  six  or  eight  bours  the  animal  is  killed,  and  the  fluid,  "which 
has  collected  in  the  isolated  portion  of  intestine,  taken  out  and 
examined.  The  above  "was  the  method  adopted  by  Frerichs.  Bid- 
der and  Schmidt,  in  order  to  obtain  pure  intestinal  juice,  first  tied 
the  biliary  and  pancreatic  ducts,  so  that  both  the  bile  and  the  pan- 
creatic juice  should  be  shut  out  from  the  intestine,  and  then  estab- 
lished an  intestinal  fistula  belo"W",  from  which  they  extracted  the 
fluids  which  accumulated  in  the  cavity  of  the  gut.  From  the  great 
abundance  of  the  follicles  of  Lieberkiihn,  we  should  expect  to  find 
the  intestinal  juice  secreted  in  large  quantity.  It  appears,  however, 
in  point  of  fact,  to  be  quite  scanty,  as  the  quantity  collected  in  the 
above  manner  by  experimenters  has  rarely  been  sufficient  for  a 
thorough  examination  of  its  properties.  It  seems  to  resemble  very 
closely,  in  its  physical  characters,  the  secretion  of  the  mucous  folli- 
cles of  the  mouth.  It  is  colorless  and  glassy  in  appearance,  viscid 
and  mucous  in  consistency,  and  has  a  distinct  alkaline  reaction. 
It  has  the  property  when  pure,  as  well  as  when  mixed  with  other 
secretions,  of  rapidly  converting  starch  into  sugar,  at  the  tempera- 
ture of  the  living  body. 

Panceeatic  Juice,  and  the  Digestion  of  Fat. — The  only  re- 
maining ingredients  of  the  food  that  require  digestion  are  the  oily 
matters.  These  are  not  afifected,  as  we  have  already  stated,  by  con- 
tact with  the  gastric  juice ;  and  examination  shows,  furthermore, 
that  they  are  not  digested  in  the  stomach.  So  long  as  they  remain 
in  the  cavity  of  this  organ  they  are  unchanged  in  their  essential 
properties.  They  are  merely  melted  by  the  warmth  of  the  stomach, 
and  set  free  by  the  solution  of  the  vesicles,  fibres,  or  capillary  tubes 
in  which  they  are  contained,  or  among  which  they  are  entangled ; 
and  are  still  readily  discernible  by  the  eye,  floating  in  larger  or 
smaller  drops  on  the  surface  of  the  semi-fluid  alimentary  mass. 
Yery  soon,  however,  after  its  entrance  into  the  intestine,  the  oily 
portion  of  the  food  loses  its  characteristic  appearance,  and  is  con- 
verted into  a  white,  opaque  emulsion,  which  is  gradually  absorbed. 
This  emulsion  is  termed  the  chyle,  and  is  always  found  in  the  small 
intestine  during  the  digestion  of  fat,  entangled  among  the  valvulse 
conniventes,  and  adhering  to  the  surface  of  the  villi.  The  digestion 
of  the  oil,  however,  and  its  conversion  into  chyle,  does  not  take 
place  at  once  upon  its  entrance  into  the  duodenum,  but  only  after 
it  has  passed  the  orifices  of  the  pancreatic  and  biliary  ducts.     Since 


154:  DIGESTION. 

these  ducts  almost  invariably  open  into  tlie  intestine  at  or  near  the 
same  point,  it  was  for  a  long  time  difficult  to  decide  bj  which  of 
the  two  secretions  the  digestion  of  the  oil  was  accomplished.  M. 
Bernard,  however,  first  threw  some  light  on  this  question  by  ex- 
perimenting on  some  of  the  lower  animals,  in  which  the  two  ducts 
open  separately.  In  the  rabbit,  for  example,  the  biliary  duct  opens 
as  usual  just  below  the  pylorus,  while  the  pancreatic  duct  com- 
municates with  the  intestine  some  eight  or  ten  inches  lower  down. 
Bernard  fed  these  animals  with  substances  containing  oil,  or  in- 
jected melted  butter  into  the  stomach  ;  and,  on  killing  them  after- 
ward, found  that  there  was  no  chyle  in  the  intestine  between  the 
opening  of  the  biliary  and  pancreatic  ducts,  but  that  it  was  abun- 
dant immediately  below  the  orifice  of  the  latter.  Above  this  point, 
also,  he  found  the  lacteals  empty  or  transparent,  while  below  it 
they  were  full  of  ivhite  and  opaque  chyle.  The  result  of  these  ex- 
periments, which  have  since  been  confirmed  by  Prof.  Samuel  Jack- 
son, of  Philadelphia,^  led  to  the  conclusion  that  the  pancreatic  fluid 
is  the  active  agent  in  the  digestion  of  oily  substances ;  and  an  ex- 
amination of  the  properties  of  this  secretion,  when  obtained  in  a 
pure  state  from  the  living  animal,  fully  confirms  the  above  opinion. 
In  order  to  obtain  pancreatic  juice  from  the  dog,  the  animal 
must  be  etherized  soon  after  digestion  has  commenced,  an  incision 
made  in  the  upper  part  of  the  abdomen,  a  little  to  the  right  of  the 
median  line,  and  a  loop  of  the  duodenum,  together  with  the  lower 
extremity  of  the  pancreas  which  lies  adjacent  to  it,  drawn  out  at 
the  external  wound.  The  pancreatic  duct  is  then  to  be  exposed 
and  opened,  and  a  small  silver  canula  inserted  into  it  and  secured 
by  a  ligature.  The  whole  is  then  returned  into  the  abdomen  and 
the  wound  closed  by  sutures,  leaving  only  the  end  of  the  canula 
projecting  from  it.  In  the  dog  there  are  two  pancreatic  ducts, 
situated  from  half  an  inch  to  an  inch  apart.  The  lower  one  of 
these,  which  is  usually  the  larger  of  the  two,  is  the  one  best  adapted 
for  the  insertion  of  the  canula.  After  the  effects  of  etherization 
have  passed  off,  and  the  digestive  process  has  recommenced,  the 
pancreatic  juice  begins  to  run  from  the  orifice  of  the  canula,  at  first 
very  slowly  and  in  drops.  Sometimes  the  drops  follow  each  other 
with  rapidity  for  a  few  moments,  and  then  an  interval  occurs  during 
which  the  secretion  seems  entirely  suspended.  After  a  time  it  re- 
commences, and  continues  to  exhibit  similar  fluctuations  during 

'  American  Jouru.  Med.  Sci.,  Oct.  1S54. 


PANCREATIC    JUICE,   AND    THE    DIGESTION    OF    FAT.      155 

the  whole  course  of  the  experiment.  Its  flow,  however,  is  at  all 
times  scanty,  compared  with  that  of  the  gastric  juice ;  and  we  have 
never  been  able  to  collect  more  than  a  little  over  two  fluidounces 
and  a  half  during  a  period  of  three  hours,  in  a  dog  weighing  not 
more  than  forty-five  pounds.  This  is  equivalent  to  about  364 
grains  per  hour ;  but  as  the  pancreatic  juice  in  the  dog  is  secreted 
with  freedom  only  during  digestion,  and  as  this  process  is  in  opera- 
tion not  more  than  twelve  hours  out  of  the  twenty-four,  the  entire 
amount  of  the  secretion  for  the  whole  day,  in  the  dog,  may  be  esti- 
mated at  4,368  grains.  This  result,  applied  to  a  man  weighing  140 
pounds,  would  give,  as  the  total  daily  quantity  of  the  pancreatic 
juice,  about  13,104  grains,  or  1,872  pounds  avoirdupois. 

Pancreatic  juice  obtained  by  the  above  process  is  a  clear,  color- 
less, somewhat  viscid  fluid,  with  a  distinct  alkaline  reaction.  Its 
composition,  according  to  the  analysis  of  Bidder  and  Schmidt,  is  as 
follows : — 

Composition  op  Pancreatic  Juice. 

Water 900.76 

Organic  matter  (pancreatine)     .......         90.38 

Chloride  of  sodium .  7.36 

Free  soda 0.32 

Pliosphate  of  soda      . 0.45 

Sulphate  of  soda 0.10 

Sulphate  of  potassa 0.02 

iLime 0.54 
Magnesia       .         .         .         .         .         .         .  0.05 

Oxide  of  iron 0.02 

1000.00 

The  most  important  ingredient  of  the  pancreatic  juice  is  its 
organic  matter,  or  pancreatine.  It  will  be  seen  that  this  is  rfiuch 
more  abundant  in  proportion  to  the  other  ingredients  of  the  secre- 
tion than  the  organic  matter  of  any  other  digestive  fluid.  It  is 
coagulable  by  heat ;  and  the  pancreatic  juice  often  solidifies  com- 
pletely on  boiling,  like  white  of  egg,  so  that  not  a  drop  of  fluid  re- 
mains after  its  coagulation.  It  is  precipitated,  furthermore,  by 
nitric  acid  and  by  alcohol,  and  also  by  sulphate  of  magnesia  in 
excess.  By  this  last  property,  it  may  be  distinguished  from  albu- 
men, which  is  not  affected  by  contact  with  sulphate  of  magnesia. 

Fresh  pancreatic  juice,  brought  into  contact  with  oily  matters  at 
the  temperature  of  the  body,  exerts  upon  them,  as  was  first  noticed 
by  Bernard,  a  very  peculiar  effect.  It  disintegrates  them,  and  re- 
duces* them  to  a  state  of  complete  emulsion,  so  that  the  mixture  is 
at  once  converted  into  a  white,  opaque,  creamy-looking  fluid.     This 


156  DIGESTION. 

effect  is  instantaneous  and  permanent,  and  only  requires  tliat  the 
two  substances  be  well  mixed  by  gentle  agitation.  It  is  singular 
that  some  of  the  German  observers  should  deny  that  the  pancreatic 
juice  possesses  the  property  of  emulsioning  fat,  to  a  greater  extent 
than  the  bile  and  some  other  digestive  fluids  ;  and  should  state  that 
although,  when  shaken  up  with  oil,  outside  the  body,  it  reduces 
the  oily  particles  to  a  state  of  extreme  minuteness,  the  emulsion 
is  not  permanent,  and  the  oily  particles  "soon  separate  again  on 
the  surface."^  We  have  frequently  repeated  this  experiment  with 
different  specimens  of  pancreatic  juice  obtained  from  the  dog,  and 
have  never  failed  to  see  that  the  emulsion  produced  by  it  is  by 
far  more  prompt  and  complete  than  that  which  takes  place  with 
saliva,  gastric  juice,  or  bile.  The  effect  produced  by  these  fluids  is 
in  fact  altogether  insignificant,  in  comparison  with  the  prompt  and 
energetic  action  exerted  by  the  pancreatic  juice.  The  emulsion 
produced  with  the  latter  secretion  may  be  kept,  furthermore,  for  at 
least  twenty-four  hours,  according  to  our  observations,  without  any 
appreciable  separation  of  the  oily  particles,  or  a  return  to  their 
original  condition. 

The  pancreatic  juice,  therefore,  is  peculiar  in  its  action  on  oily 
substances,  and  reduces  them  at  once  to  the  condition  of  an  emul- 
sion. The  oil,  in  this  process,  does  not  suffer  any  chemical  altera- 
tion. It  is  not  decomposed  or  saponified,  to  any  appreciable  extent. 
It  is  simply  emulsioned  ;  that  is,  it  is  broken  up  into  a  state  of  minute 
subdivision,  and  retained  in  suspension,  by  contact  with  the  organic 
matter  of  the  pancreatic  juice.  That  its  chemical  condition  is  not 
altered  is  shown  by  the  fact  that  it  is  still  soluble  in  ether,  which 
will  withdraw  the  greater  part  of  the  fat  from  a  mixture  of  oil  and 
pancreatic  juice,  as  well  as  from  the  chyle  in  the  interior  of  the 
intestine.  In  a  state  of  emulsion,  the  fat,  furthermore,  is  capable 
of  being  absorbed,  and  its  digestion  may  be  then  said  to  be  accom- 
plished. 

We  find,  then,  that  the  digestion  of  the  food  is  not  a  simple 
operation,  but  is  made  up  of  several  different  processes,  which 
commence  successively  in  different  portions  of  the  alimentary 
canal.  In  the  first  place,  the  food  is  subjected  in  the  mouth  to  the 
physical  operations  of  mastication  and  insalivation.  Eeduced  to  a 
soft  pulp  and  mixed  abundantly  with  the  saliva,  it  passes,  secondly, 
into  the  stomach.     Here  it  excites  the  secretion  of  the  gastric  juice, 

'  Lelimann's  Physiological  Chemistry.     Philada.  ed.,  vol.  i.  p.  507. 


PHENOMENA    OF    INTESTINAL    DIGESTION.  157 

hy  the  influence  of  which  its  chemical  transformation  and  solution 
are  commenced.  If  the  meal  consist  wholly  or  partially  of  mus- 
cular flesh,  the  first  effect  of  the  gastric  juice  is  to  dissolve  the 
intervening  cellular  substance,  by  which  the  tissue  is  disintegrated 
and  the  muscular  fibres  separated  from  each  other.  Afterward 
the  muscular  fibres  themselves  become  swollen  and  softened  by 
the  imbibition  of  the  gastric  fluid,  and  are  finally  disintegrated 
and  liquefied.  In  the  small  intestine,  the  pancreatic  and  intestinal 
juices  convert  the  starchy  ingredients  of  the  food  into  sugar,  and 
break  up  the  fatty  matters  into  a  fine  emulsion,  by  which  they  are 
converted  into  chyle. 

Although  the  separate  actions  of  these  digestive  fluids,  however, 
commence  at  different  points  of  the  alimentary  canal,  they  after- 
ward go  on  simultaneously  in  the  small  intestine ;  and  the  changes 
which  take  place  here,  and  which  constitute  the  process  of  intestinal 
digestion,  form  at  the  same  time  one  of  the  most  complicated,  and 
one  of  the  most  important  parts  of  the  whole  digestive  function. 

The  phenomena  of  intestinal  digestion  may  be  studied,  in  the 
dog,  by  killing  the  animal  at  various  periods  after  feeding,  and 
examining  the  contents  of  the  intestine.  We  have  also  succeeded, 
by  establishing  in  the  same  animal  an  artificial  intestinal  fistula, 
in  gaining  still  more  satisfactory  information  on  this  point.  The 
fistula  may  be  established,  for  this  purpose,  by  an  operation  precisely 
similar  to  that  already  described  as  employed  for  the  production  of 
a  permanent  fistula  in  the  stomach.  The  silver  tube  having  been 
introduced  into  the  lower  part  of  the  duodenum,  the  wound  is 
allowed  to  heal,  and  the  intestinal  secretions  may  then  be  with- 
drawn at  will,  and  subjected  to  examination  at  different  periods 
during  digestion. 

By  examining  in  this  way,  from  time  to  time,  the  intestinal 
fluids,  it  at  once  becomes  manifest  that  the  action  of  the  gastric 
juice,  in  the  digestion  of  albuminoid  substances,  is  not  confined  to 
the  stomach,  but  continues  after  the  food  has  passed  into  the  intes- 
tine. About  half  an  hour  after  the  ingestion  of  a  meal,  the  gastric 
juice  begins  to  pass  into  the  duodenum,  where  it  may  be  recognized 
by  its  strongly-marked  acidity,  and  by  its  peculiar  action,  already 
described,  in  interfering  with  Trommer's  test  for  grape  sugar.  It 
has  accordingly  already  dissolved  some  of  the  ingredients  of  the 
food  while  still  in  the  stomach,  and  contains  a  certain  quantity  of 
albuminose  in  solution.  It  soon  afterward,  as  it  continues  to  pass 
into  the  duodenum,  becomes  mingled  with  the  debris  of  muscular 


158 


DIGESTION'. 


Contents  of  Stomach  during  Digestion 
OF  Meat,  from  the  Dog. — a.  Fat  Vesicle,  filled  with 
opaque,  solid,  granular  fat.  b,  b.  Bits  of  partially 
di.-iutegrated  muscular  fibre,     c.   Oil  globules. 


fibres,  fat  vesicles,  and   oil   drops;    substances  wbicli   are   easily 

recognizable  under  the  microscope,  and  which  produce  a  grayish 

„.    „„  turbidity  in  the  fluid  drawn 

Fig.  33.  -^  .     -        . 

from  the  fistula.     This  turbid 

admixture  grows  constantly 
thicker  from  the  second  to 
the  tenth  or  twelfth  hour; 
after  which  the  intestinal 
fluids  become  less  abundant, 
and  finally  disappear  almost 
entirely,  as  the  process  of  di- 
gestion comes  to  an  end. 

The  passage  of  disintegrated 
muscular  tissue  into  the  intes- 
tine may  also  be  shown,  as 
already  mentioned,  by  killing 
the  animal  and  examining 
the  contents  of  the  alimentary 
canal.  During  the  digestion 
of  muscular  flesh  and  adipose 
tissue,  the  stomach  contains 
masses  of  softened  meat, 
smeared  over  with  gastric 
juice,  and  also  a  moderate 
quantity  of  grayish,  grumous 
fluid,  with  an  acid  reaction. 
This  fluid  contains  muscular 
fibres,  isolated  from  each 
other,  and  more  or  less  dis- 
integrated, by  the  action  of 
the  gastric  juice.  (Fig.  83.) 
The  fat  vesicles  are  but  little 
or  not  at  all  altered  in  the 
stomach,  and  there  are  only 
a  few  free  oil  globules  to  be 
seen  floating  in  the  mixed 
fluids,  contained  in  the  cavity 
In  the  duodenum  the  muscular  fibres  are  further 
They  become  very  much  broken  up,  pale 


Fig.  34. 


"From  Duodenum  of  Dog,  during  Diges- 
tion OF  Meat. — a.  Pat  Vesicle,  with  its  contents 
diminishing.  The  vesicle  is  beginning  to  shrivel  and 
the  fat  breaking  up.  6,  b.  Disintegrated  muscular 
fibre,     c,  c.  Oil  Globules. 


of  the  organ 

disintegrated.  (Fig.  34.) 

and  transparent,  but  can  still  be  recognized  by  the  granular  mark 

ings  and  striations  which  are  characteristic  of  them.     The  fat  vesi 


PHENOMENA    OF    INTESTINAL    DIGESTION. 


159 


Fig.  35. 


cles  also  begin  to  become  altered  in  the  duodenum.  The  solid 
granular  fat  of  beef,  and  similar  kinds  of  meat,  becomes  lic[uefiecl 
and  emulsioned;  and  appears 
•under  the  form  of  free  oil 
drops  and  fattj  molecules; 
while  the  fat  vesicle  itself  is 
partially  emptied,  and  becomes 
more  or  less  collapsed  and 
shrivelled.  In  the  middle 
and  lower  parts  of  the  intes- 
tine (Figs.  35  and  36)  these 
changes  continue.  The  mus- 
cular fibres  become  constantly 
more  and  more  disintegrated, 
and  a  large  quantity  of  granu- 
lar debris  is  produced,  which 
is  at  last  also  dissolved.     The 

From  Middi.kop  Small  Ixtestike.- 
fat    also     progressively    disap-    Fat  vesicles,  nearly  emptied  of  theitconteats. 


Fig.  36. 


pears,  and  the  vesicles  may 
be  seen  in  the  lower  part  of 
the  intestine,  entirely  collapsed 
and  empty. 

In  this  way  the  digestion  of 
the  different  ingredients  of 
the  food  goes  on  in  a  continu- 
ous manner,  from  the  stomach 
throughout  the  entire  length 
of  the  small  intestine.  At  the 
same  time,  it  results  in  the 
production  of  three  different 
substances,  viz  :  1st.  Albumi- 
nose,  produced  by  the  action 

r.    ,1  ,    •        •     •  ,1  From  LAST  QUAKTER  OP  Small  Intkstink. 

of    the     gastric     juice     on     the    _«,„.  F,t  vesicles,  quite  empty  and  .hnvelW. 

albuminoid  matters ;    2d.  An 

oily  emulsion,  produced  by  the  action  of  the  pancreatic  juice  on 
fat ;  and,  3d.  Sugar,  produced  from  the  transformation  of  starch 
by  the  mixed  intestinal  fluids.  These  substances  are  then  ready 
to  be  taken  up  into  the  circulation ;  and  as  the  mingled  ingredients 
of  the  intestinal  contents  pass  successively  downward,  through  the 
duodenum,  jejunum,  and  ileum,  the  products  of  digestion,  together 
with  the  digestive  secretions  themselves,  are  gradually  absorbed, 


160  DIGESTION. 

one  after  another,  by  the  vessels  of  tlie  mucous  membrane,  and 
carried  away  by  tbe  current  of  the  circulation. 

The  Lakge  Intestine  and  its  Contents. — Throughout  the 
small  intestine,  as  we  have  just  seen,  the  secretions  are  intended 
exclusively  or  mainly  to  act  upon  the  food,  to  liquefy  or  disinte- 
grate it,  and  to  prepare  it  for  absorption.  But  below  the  situation 
of  the  ileo-cgecal  valve,  and  throughout  the  large  intestine,  the  con- 
tents of  the  alimentary  canal  exhibit  a  different  appearance,  and 
are  distinct  in  their  color,  odor,  and  consistency.  This  portion  of 
the  intestinal  contents,  or  the  feces,  are  not  composed,  for  the  most 
part,  of  the  undigested  remains  of  the  food,  but  consist  principally 
of  animal  substances  discharged  into  the  intestine  by  excretion. 
These  substances  have  not  all  been  fully  investigated ;  for  although 
they  are  undoubtedly  of  great  importance  in  regard  to  the  preser- 
vation of  health,  yet  the  peculiar  manner  in  which  they  are  dis- 
charged by  the  mucous  membrane  and  united  with  each  other  in 
the  feces  has  interfered,  to  a  great  extent,  with  a  thorough  investi- 
gation of  their  physiological  characters.  Those  which  have  been 
most  fully  examined  are  the  following : — ■ 

Excretine. — This  was  discovered  and  described  by  Dr.  W.  Mar- 
cet,'  as  the  most  characteristic  ingredient  in  the  contents  of  the 
large  intestine.  It  is  a  slightly  alkaline,  crystallizable  substance, 
insoluble  in  water,  but  soluble  in  ether  and  hot  alcohol.  It  crys- 
tallizes in  radiated  groups  of  four-sided  prismatic  needles.  It  fuses 
at  204°  F.,  and  burns  at  a  higher  temperature.  It  is  non-nitrogen- 
ous, and  consists  of  carbon,  hydrogen,  oxygen,  and  sulphur,  in  the 
following  proportions : — 

C78  H73  O2  s. 

It  is  thought  to  be  present  mostly  in  a  free  state,  but  partly  in  union 
with  certain  organic  acids,  as  a  saline  compound. 

Stercorine. — This  substance  was  found  to  be  an  ingredient  of  the 
human  feces  by  Prof.  A.  Flint,  Jr.^  It  is  soluble  in  ether  and 
boiling  alcohol,  and,  like  excretine,  crystallizes  in  the  form  of 
radiating  needles,  but  fuses  at  a  much  lower  temperature.  It  is 
regarded  by  its  discoverer  as  produced,  by  transformation,  from 
cholesterine,  one  of  the  ingredients  of  the  bile. 

Beside  these  substances,  the  feces  contain  a  certain  amount  of 

•  American  Journal  of  the  Medical  Sciences,  January,  1855,  and  January,  1858. 
«  Ibid.,  October,  1862. 


THE    LAKGE    INTESTINE    AND    ITS    CONTENTS.  161 

fat,  fatty  acids,  and  the  remnants  of  undigested  food.  Vegetable 
cells  and  fibres  may  be  detected,  and  some  debris  of  the  disin- 
tegrated muscular  fibres  may  almost  always  be  found  after  a  meal 
composed  of  animal  and  vegetable  substances.  But  little  absorp- 
tion, accordingly,  takes  place  in  the  large  intestine.  Its  office  is 
mainly  confined  to  the  separation  and  discharge  of  certain  excre- 
mentitious  substances. 


11 


162 


ABSORPTION. 


CHAPTER    VII. 


ABSORPTION. 


Beside  the  glands  of  Brunner  and  the  follicles  of  LieberkUhn, 
already  described,  there  are,  in  the  inner  part  of  the  walls  of  the 

intestine,  certain   glandular- 
■^'S*    '•  looking    bodies    which    are 

termed  "  gland ulae  solitari^," 
and  "  glandulas  agminatee." 
The  glandulae  solitariae  are 
globular  or  ovoid  bodies, 
about  one-thirtieth  of  an  inch 
in  diameter,  situated  partly 
in  and  partly  beneath  the  in- 
testinal mucous  membrane. 
Each  glandule  (Fig.  87)  is 
formed  of  an  investing  cap- 
sule, closed  on  all  sides,  and 
containing  in  its  interior  a 
soft  pulpy  mass,  which  con- 

0>fF,  OFTnECLosEDFoi,  I.  iclesofPever's       ^         ■*■       '■  y 
Patches,  from    Small  latestioe  of  Pit?.     MaguiQed     sistS  of  minutC  CCllular  bodicS, 

50  diameter-.  imbedded  in  a  homogeneous 

substance.  The  inclosed  mass 
is  penetrated  by  capillary 
bloodvessels,  which  pass  in 
through  the  investing  cap- 
sule, inosculate  freely  with 
each  other,  and  return  upon 
themselves  in  loops  near  the 
centre  of  the  glandular  body. 
There  is  no  external  opening 
or  duct;  in  fact,  the  contents 
of  the  vesicle,  being  pulpy 
and  vascular,  as  already  de- 
scribed, are  not  to  be  regarded 
as  a  secretion,  but  as  consti- 

Glandpl^   Agminat.^,   from    Small   Intestine  ,  i   •      i       />       t  i        t        j 

of  Pig.     Magnified  20  diameters.  tutmg  a  Lmd  of  SoM    gUud- 


Fie.  38. 


ABSORPTION". 


Wi 


Fig.  39. 


tissue.  The  glandulae  agminatae  (Fig.  38),  or  "  Peyer's  patches,"  as 
they  are  sometimes  called,  consist  of  aggregations  of  similar  globular 
or  ovoid  bodies,  found  most  abundantly  toward  the  lower  extremity 
of  the  small  intestine.  Both  the  solitary  and  agminated  glandules 
are  evidently  connected  with  the  lacteals  and  the  system  of  the 
mesenteric  glands,  which  latter  organs  they  resemble  very  much  in 
their  minute  structure.  They  are  probably  to  be  regarded  as  the 
first  row  of  mesenteric  glands,  situated  in  the  walls  of  the  intestinal 
canal. 

Another  set  of  organs,  intimately  connected  with  the  process  of 
absorption,  are  the  villi  of  the  small  intestine.  These  are  conical 
vascular  eminences  of  the  mucous  membrane,  thickly  set  over  the 
whole  internal  surface  of  the  small  intestine.  In  the  upper  portion  of 
the  intestine,  they  are  flattened  and  triangular  in  form,  resembling 
somewhat  the  conical  projections  of  the  pyloric  portion  of  the  sto- 
mach. In  the  lower  part  they  are  long  and  filiform,  and  often 
slightly  enlarged,  or  club-shaped  at  their  free  extremity  (Fig.  89), 
and  frequently  attaining  the  length  of 
one  thirty-fifth  of  an  inch.  They  are 
covered  externally  with  a  layer  of 
columnar  epithelium,  similar  to  that 
which  lines  the  rest  of  the  intestinal 
mucous  membrane,  and  contain  in  their 
interior  two  sets  of  vessels.  The  most 
superficial  of  these  are  the  capillary 
bloodvessels,  which  are  supplied  in  each 
villus  by  a  twig  of  the  mesenteric 
artery,  and  which  form,  by  their  fre- 
quent inosculation,  an  exceedingly  close 
and  abundant  network,  almost  imme- 
diately beneath  the  epithelial  layer. 
They  unite  at  the  base  of  the  villus, 
and  form  a  minute  vein,  which  is  one 
of  the  commencing  rootlets  of  the  por- 
tal vein.  In  the  central  part  of  the  vil- 
lus, and  lying  nearly  in  its  axis,  there 
is  another  vessel,  with  thinner  and  more 

transparent  walls,  which  is  the  commencement  of  a  lacteal.  The 
precise  manner  in  which  the  lacteal  originates  in  the  extremity  of 
the  villus  is  not  known.  It  commences  near  the  apex,  either  by  a 
blind  extremity,  or  by  an  irregular  plexus,  passes,  in  a  straight  or 


KXT  REMIT  if         OF        IjJTESTINAl 

Villus,  from  the  Dog.— n.  Layer  of 
epithelmm.  b.  Bloodvessel,  c.  Lacteal 
vessel. 


164  ABSORPTION. 

somewhat  wavy  line,  toward  the  base  of  the  villus,  and  then  be- 
comes continuous  with  a  small  twig  of  the  mesenteric  lacteals. 

The  villi  are  the  active  agents  in  the  process  of  absorption.  B j 
their  projecting  form,  and  their  great  abundance,  thej  increase  enor- 
mously the  extent  of  surface  over  which  the  digested  fluids  come 
in  contact  with  the  intestinal  mucous  membrane,  and  increase,  also, 
to  a  corresponding  degree,  the  energy  with  which  absorption  takes 
place.  They  hang  out  into  the  nutritious,  semi-fluid  mass  contained 
in  the  intestinal  cavity,  as  the  roots  of  a  tree  penetrate  the  soil ;  and 
they  imbibe  the  liquefied  portions  of  the  food,  with  a  rapidity  which 
is  in  direct  proportion  to  their  extent  of  surface,  and  the  activity  of 
their  circulation. 

The  process  of  absorption  is  also  hastened  by  the  peristaltic 
movements  of  the  intestine.  The  muscular  layer  here,  as  in  other 
parts  of  the  alimentary  canal,  is  double,  consisting  of  both  circular 
and  longitudinal  fibres.  The  action  of  these  fibres  may  be  readily 
seen  by  pinching  the  exposed  intestine  with  the  blades  of  a  forceps. 
A  contraction  then  takes  place  at  the  spot  irritated,  by  which  the 
intestine  is  reduced  in  diameter,  its  cavity  obliterated,  and  its  con- 
tents forced  onward  into  the  succeeding  portion  of  the  alimentary 
canal.  The  local  contraction  then  propagates  itself  to  the  neighbor- 
ing parts,  while  the  portion  originally  contracted  becomes  relaxed ; 
so  that  a  slow,  continuous,  creeping  motion  of  the  intestine  is  pro- 
duced, by  successive  waves  of  contraction  and  relaxation,  which 
follow  each  other  from  above  downward.  At  the  same  time,  the 
longitudinal  fibres  have  a  similar  alternating  action,  drawing  the 
narrowed  portions  of  intestine  up  and  down,  as  they  successively 
enter  into  contraction,  or  become  relaxed  in  the  intervals.  The  effect 
of  the  whole  is  to  produce  a  peculiar,  writhing,  worm-like,  or 
"vermicular"  motion,  among  the  different  coils  of  intestine.  During 
life,  the  vermicular  or  peristaltic  motion  of  the  intestine  is  excited 
by  the  presence  of  food  undergoing  digestion.  By  its  action,  the 
substances  which  pass  from  the  stomach  into  the  intestine  are 
steadily  carried  from  above  downward,  so  as  to  traverse  the  entire 
length  of  the  small  intestine,  and  to  come  in  contact  successively 
with  the  whole  extent  of  its  mucous  membrane.  During  this  pas- 
sage, the  absorption  of  the  digested  food  is  constantly  going  on. 
Its  liquefied  portions  are  taken  up  by  the  villi  of  the  mucous  mem- 
brane, and  successively  disappear ;  so  that,  at  the  termination  of  the 
small  intestine,  there  remains  only  the  undigestible  portion  of  the 
food,  together  with  the  refuse  of  the  intestinal  secretions.     These 


ABSORPTIOISr.  165 

pass  through  the  ileo-csecal  orifice  into  the  large  intestine,  and  there 
become  reduced  to  the  condition  of  feces. 

The  absorption  of  the  digested  fluids  is  accomplished  both  by 
the  bloodvessels  and  the  lacteals.  It  was  formerly  supposed  that 
the  lacteals  were  the  only  agents  in  this  process ;  but  it  has  now 
been  long  known  that  this  opinion  was  erroneous,  and  that  the 
bloodvessels  take  at  least  an  equal  part  in  absorption,  and  are  in 
some  respects  the  most  active  and  important  agents  of  the  two. 
Abundant  experiments  have  demonstrated  not  only  that  soluble 
substances  introduced  into  the  intestine  may  be  soon  afterward 
detected  in  the  blood  of  the  portal  vein,  but  that  absorption  takes 
place  more  rapidly  and  abundantly  by  the  bloodvessels  than  by 
the  lacteals.  The  most  decisive  of  these  experiments  were  those 
performed  by  Panizza  on  the  abdominal  circulation,'  This  ob- 
server opened  the  abdomen  of  a  horse,  and  drew  out  a  fold  of  the 
small  intestine,  eight  or  nine  inches  in  length  (Fig.  40,  a,  a),  which 

Fig.  40. 


Pakizza'b  Expekiment. — 'la.  Intestine.    6.  Point  of  ligatnre  of  mesenteric  vein.   c.  Opening 
in  intestine  for  introduction  of  poison,     d.  Opening  in  mesenteric  vein  behind  the  ligature. 

he  included  between  two  ligatures.  A  ligature  was  then  placed  (at 
&)  upon  the  mesenteric  vein  receiving  the  blood  from  this  portion 
of  intestine ;  and,  in  order  that  the  circulation  might  not  be  inter- 
rupted, an  opening  was  made  (at  d)  in  the  vein  behind  the  ligature, 
so  that  the  blood  brought  by  the  mesenteric  artery,  after  circulating 

'  In  Matteucci's  Lectures  on  the  Physical  Phenomena  of  Living  Beings,  Pereira's 
edition,  p.  83. 


166  ABSOKPTION. 

ia  the  intestinal  capillaries,  passed  out  at  the  opening,  and  was 
collected  in  a  vessel  for  examination.  Hydrocyanic  acid  was  then 
introduced  into  the  intestine  by  an  opening  at  c,  and  almost  imme- 
diately afterward  its  presence  was  detected  in  the  venous  blood 
flowing  from  the  orifice  at  d.  The  animal,  however,  was  not  poi- 
soned, since  the  acid  was  prevented  from  gaining  an  entrance  into 
the  general  circulation  by  the  ligature  at  h. 

Panizza  afterward  varied  this  experiment  in  the  following  man- 
ner :  Instead  of  tying  the  mesenteric  vein,  he  simply  compressed  it. 
Then,  hydrocyanic  acid  being  introduced  into  the  intestine,  as  above, 
no  effect  was  produced  on  the  animal,  so  long  as  compression  was 
maintained  upon  the  vein.  But  as  soon  as  the  blood  was  allowed 
to  pass  again  through  the  vessels,  symptoms  of  general  poisoning 
at  once  became  manifest.  Lastly,  in  a  third  experiment,  the  same 
observer  removed  all  the  nerves  and  lacteal  vessels  supplying  the 
intestinal  fold,  leaving  the  bloodvessels  alone  untouched.  Hydro- 
cyanic acid  now  being  introduced  into  the  intestine,  found  an 
entrance  at  once  into  the  general  circulation,  and  the  animal  was 
immediately  poisoned.  The  bloodvessels,  therefore,  are  not  only 
capable  of  absorbing  fluids  from  the  intestine,  but  may  even  take 
them  up  more  rapidly  and  abundantly  than  the  lacteals. 

These  two  sets  of  vessels,  however,  do  not  absorb  all  the  aliment- 
ary matters  indiscriminately.  It  is  one  of  the  most  important  of 
the  facts  which  have  been  established  by  modern  researches  on 
digestion  that  the  different  substances,  produced  by  the  operation  of 
the  digestive  fluids  on  the  food,  pass  into  the  circulation  by  different 
routes.  The  fatty  matters  are  taken  up  by  the  lacteals  under  the  form 
of  chyle,  while  the  saccharine  and  albuminous  matters  pass  by  ab- 
sorption into  the  portal  vein.  Accordingly,  after  the  digestion  of  a 
meal  containing  starchy  and  animal  matters  mixed,  albuminose  and 
sugar  are  both  found  in  the  blood  of  the  portal  vein,  while  they  can- 
not be  detected,  in  any  large  quantity,  in  the  contents  of  the  lacteals. 
These  substances,  however,  do  not  mingle  at  once  with  the  general 
mass  of  the  circulation,  but  owing  to  the  anatomical  distribution  of 
the  portal  vein,  pass  first  through  the  capillary  circulation  of  the 
liver.  Soon  after  being  introduced  into  the  blood  and  coming  in 
contact  with  its  organic  ingredients,  they  become  altered  and  con- 
verted, by  catalytic  transformation,  into  other  substances.  The 
albuminose  passes  into  the  condition  of  ordinary  albumen,  and 
probably  also  partly  into  that  of  fibrin ;  while  the  sugar  rapidly 
becomes  decomposed,  and   loses  its  characteristic   properties;    so 


ABSORPTION'. 


167 


that,  on  arriving  at  the  entrance  of  the  general  circulation,  both 
these  newly  absorbed  ingredients  have  become  already  assimilated 
to  those  which  previously  existed  in  the  blood. 

The  chyle  in  the  intestine  consists,  as  we  have  already  mentioned, 
of  oily  matters  which  have  not  been  chemically  altered,  but  simpH 
reduced  to  a  state  of  emulsion.  In  chyle  drawn  from  the  lacteals 
or  the  thoracic  duct  (Fig.  41),  it  still  presents  itself  in  the  same 
condition  and  retains  all  the 

chemical    properties    of    oil.  f'??-  41. 

Examined  by  the  microscope, 
it  is  seen  to  exist  under  the 
form  of  fine  granules  and 
molecules,  which  present  the 
ordinary  appearances  of  oil 
in  a  state  of  minute  subdivi- 
sion. The  chyle,  therefore, 
does  not  represent  the  entire 
product  of  the  digestive  pro- 
cess, but  contains  only  the 
fatty  substances,  suspended 
by  emulsion  in  a  serous  fluid. 

During  the  time  that  intes- 
tinal absorption  is  going  on, 
after  a  meal  containing  fatty 
ingredients,  the  lacteals  may 

be  seen  as  white,  opaque  vessels,  distended  with  milky  chyle,  pass- 
ing through,  the  mesentery,  and  converging  from  its  intestinal  bor- 
der toward  the  receptaculum  chyli,  near  the  spinal  column.  During 
their  course,  they  pass  through  several  successive  rows  of  mesenteric 
glands,  which  also  become  turgid  with  chyle,  while  the  process  of 
digestion  is  going  on.  The  lacteals  then  conduct  the  chyle  to  the 
receptaculum  chyli,  whence  it  passes  upward  through  the  thoracic 
duct,  and  is  finally  discharged,  at  the  termination  of  this  canal,  into 
the  left  subclavian  vein.  (Fig.  42.)  It  is  then  mingled  with  the 
returning  current  of  venous  blood,  and  passes  into  the  right  cavities 
of  the  heart. 

The  lacteals,  however,  are  not  a  special  system  of  vessels  by  them- 
selves, but  are  simply  a  part  of  the  great  system  of  "  absorbent"  or 
"  lymphatic"  vessels,  which  are  to  be  found  everywhere  in  the  integu- 
ments of  the  head,  the  parietes  of  the  trunk,  the  upper  and  lower 
extremities,  and  in  the  muscular  tissues  and  mucous  membranes 


Chtle  from  commenckmfnt  of  Thorac^th 
Duct,  from  the  Do?.— The  molecules  vary  in  size 
from  l-10,000th  of  au  inch  downward. 


168 


ABSORPTIOX. 


throughout  the  body.  The  walls  of  these  vessels  are  thinner  and 
more  transparent  than  those  of  the  arteries  and  veins,  and  thej  are 
consequently  less  easily  detected  by  ordinary  dissection.     They 

originate  in  the  tissues  of  the 
above-mentioned  parts  by  an 
irregular  plexus.  They  pass 
from  the  extremities  toward 
the  trunk,  converging  and 
uniting  with  each  other  like  the 
veins,  their  principal  branches 
taking  usually  the  same  di- 
rection with  the  nerves  and 
bloodvessels,  and  passing,  at 
various  points  in  their  course, 
through  certain  glandular  bo- 
dies, the  ''  lymphatic"  or  "ab- 
sorbent" glands.  The  lym- 
phatic glands,  among  which 
are  included  the  mesenteric 
glands,  consist  of  an  external 
layer  of  fibrous  tissue  and  a 
contained  pulp  or  parenchy- 
ma. The  investing  layer  of 
fibrous  tissue  sends  off  thin 
septa  or  laminae  from  its  in- 
ternal surface,  which  pene- 
trate the  substance  of  the  gland 
in  every  direction  and  unite 
with  each  other  at  various 
points.  In  this  way  they  form 
an  interlacing  laminated  framework,  which  divides  the  substance 
of  the  gland  into  numerous  rounded  spaces  or  alveoli.  These  alveoli 
are  not  completely  isolated,  but  communicate  with  each  other  by 
narrow  openings,  where  the  intervening  septa  are  incomplete.  These 
cavities  are  filled  with  a  soft,  reddish  pulp,  which  is  penetrated, 
according  to  Kolliker,  like  the  solitary  and  agminated  glands  of  the 
intestine,  by  a  fine  network  of  capillary  bloodvessels.  The  solitary 
and  agminated  glands  of  the  intestine  are,  therefore,  closely  analo- 
gous in  their  structure  to  the  lymphatics.  The  former  are  to  be 
regarded  as  simple,  the  latter  as  compound  vascular  glands. 

The  arrangement  of  the  lymphatic  vessels  in  the  interior  of  the 


-a. 

Lacteals,  Thoracic  Duct,  &c.— a.  Intes- 
tine. 6.  Vena  cava  inferior.  c,  c.  Eight  and  left 
subclavian  veins,  d.  Point  of  opening  of  thoracic 
duct  into  left  subclavian. 


ABSORPTIOX.  169 

glands  is  not  precisely  understood.  Each  lymphatic  vessel,  as  it 
enters  the  gland,  breaks  up  into  a  number  of  minute  ramifications, 
the  vasa  afferentia  ;  and  other  similar  twigs,  forming  the  vasa  effer- 
entia,  pass  off  in  the  opposite  direction,  from  the  farther  side  of  the 
gland ;  but  the  exact  mode  of  communication  between  the  two  has 
not  been  definitely  ascertained.  The  fluids,  however,  arriving  by 
the  vasa  afferentia,  must  pass  in  some  way  through  the  tissue  of 
the  gland,  before  they  are  carried  away  again  by  the  vasa  efferentia. 
From  the  lower  extremities  the  lymphatic  vessels  enter  the  abdomen 
at  the  groin  and  converge  toward  the  receptaculum  chyli,  into 
which  their  fluid  is  discharged,  and  afterward  conveyed,  by  the 
thoracic  duct,  to  the  left  subclavian  vein. 

The  fluid  which  these  vessels  contain  is  called  the  lymph.  It  is 
a  colorless  or  slightly  yellowish  transparent  fluid,  which  is  absorbed 
by  the  lymphatic  vessels  from  the  tissues  in  which  they  originate. 
So  far  as  regards  its  composition,  it  is  known  to  contain,  beside 
water  and  saline  matters,  a  small  quantity  of  fibrin  and  albumen. 
Its  ingredients  are  evidently  derived  from  the  metamorphosis  of 
the  tissues,  and  are  returned  to  the  centre  of  the  circulation  in 
order  to  be  eliminated  by  excretion,  or  in  order  to  undergo  some 
new  transforming  or  renovating  process.  "We  are  ignorant,  how- 
ever, with  regard  to  the  precise  nature  of  their  character  and 
destination. 

The  lacteals  are  simply  that  portion  of  the  absorbents  which 
originate  in  the  mucous  membrane  of  the  small  intestine.  During 
the  intervals  of  digestion,  these  vessels  contain  a  colorless  and 
transparent  lymph,  entirely  similar  to  that  which  is  found  in  other 
parts  of  the  absorbent  system.  After  a  meal  containing  only 
starchy  or  albuminoid  substances,  there  is  no  apparent  change  in 
the  character  of  their  contents.  But  after  a  meal  containing  fatty 
matters,  these  substances  are  taken  up  by  the  absorbents  of  the 
intestine,  which  then  become  filled  with  the  white  chylous  emul- 
sion, and  assume  the  appearance  of  lacteals.  (Fig.  43.)  It  is  for 
this  reason  that  lacteal  vessels  do  not  show  themselves  upon  the 
stomach  nor  upon  the  first  few  inches  of  the  duodenum ;  because 
oleaginous  matters,  as  we  have  seen,  are  not  digested  in  the  stomach, 
but  only  after  they  have  entered  the  intestine  and  passed  the  orifice 
of  the  pancreatic  duct. 

The  presence  of  chyle  in  the  lacteals  is,  therefore,  not  a  con- 
stant, but  only  a  periodical  phenomenon.  The  fatty  substances 
constituting  the  chyle  begin  to  be  absorbed  during  the  process  of 


170 


ABSORFTIOX. 


digestion,  as  soon  as  they  have  been  disintegrated  and  emulsioned 
hy  the  action  of  the  intestinal  fluids.  As  digestion  proceeds,  thej 
accumulate  in  larger  quantity,  and  gradually  fill  the  whole  lacteal 


Fi>.  43. 


LaCTEALS   and    LVJIPHATICS. 


system  and  the  thoracic  duct.  As  they  are  discharged  into  the 
subclavian  vein,  and  mingled  with  the  blood,  they  can  still  be  dis- 
tinguished in  the  circulating  fluid,  as  a  mixture  of  oily  molecules 
and  granules,  between  the  orifice  of  the  thoracic  duct  and  the  right 
side  of  the  heart.  While  passing  through  the  pulmonary  circula- 
tion, however,  they  disappear.  Precisely  what  becomes  of  them, 
or  what  particular  chemical  changes  they  undergo,  is  not  certainly 


ACSORl'TION".  171 

known.  They  are,  at  all  events,  so  altered  in  the  blood,  while 
passing  through  the  lungs,  that  they  lose  the  form  of  a  fatty  emul- 
sion, and  are  no  longer  to  be  recognized  by  the  usual  tests  for 
oleaginous  substances. 

The  absorption  of  fat  from  the  intestine  is  not,  however,  exclu- 
sively performed  by  the  lacteals.  Some  of  it  is  also  taken  up, 
under  the  same  form,  by  the  bloodvessels.  It  has  been  ascertained 
by  the  experiments  of  Bernard'  that  the  blood  of  the  mesenteric 
veins,  in  the  carnivorous  animals,  contains,  during  intestinal  diges- 
tion, a  considerable  amount  of  fatty  matter  in  a  state  of  minute 
subdivision.  Other  observers,  also  (Lehmann,  Schultz,  Simon),  have 
found  the  blood  of  the  portal  vein  to  be  considerably  richer  in  fat 
than  that  of  other  veins,  particularly  while  intestinal  digestion  is 
going  on  with  activity.  In  birds,  reptiles,  and  fish,  furthermore, 
according  to  Bernard,  the  intestinal  lymphatics  are  never  filled 
with  opaque  chyle,  but  only  with  a  transparent  lymph ;  so  that  these 
animals  may  be  said  to  be  destitute  of  lacteals,  and  in  them  the  fatty 
substances,  like  other  alimentary  materials,  are  taken  up  altogether 
by  the  bloodvessels.  In  quadrupeds,  on  the  other  hand,  and  in 
the  human  subject,  the  absorption  of  fat  is  accomplished  both  by 
the  bloodvessels  and  the  lacteals.  A  certain  portion  is  taken  up 
by  the  former,  while  the  superabundance  of  the  fatty  emulsion  is 
absorbed  by  the  latter. 

A  difficulty  has  long  been  experienced  in  accounting  for  the  ab- 
sorption of  fat  from  the  intestine,  owing  to  its  being  considered  as  a 
non-endosmotic  substance ;  that  is,  as  incapable,  in  its  free  or  undis- 
solved condition,  of  penetrating  and  passing  through  an  animal 
membrane  by  endosmosis.  It  is  stated,  indeed,  that  if  a  fine  oily 
emulsion  be  placed  on  one  side  of  an  animal  membrane  in  an  endos- 
mometer,  and  pure  water  on  the  other,  the  water  will  readily  pene- 
trate the  substance  of  the  membrane,  while  the  oily  particles  cannot 
be  made  to  pass,  even  under  a  high  pressure.  Though  this  be  true, 
however,  for  pure  water,  it  is  not  true  for  slightly  alkaline  fluids, 
like  the  serum  of  the  blood  and  the  lymph.  This  has  been  de- 
monstrated by  the  experiments  of  Matteucci,  in  which  he  made 
an  emulsion  with  an  alkaline  fluid  containing  43  parts  per  thou- 
sand of  caustic  potassa.  Such  a  solution  has  no  perceptible  alkaline 
taste,  and  its  action  on  reddened  litmus  paper  is  about  equal  to 
that  of  the  lymph  and  chyle.     If  this  emulsion  were  placed  in  an 

'  Lemons  dt»  Physiologic  Experimentale.     Paris,  185G,  p.  325. 


172 


ABSORPTION 


Intestinal  Epithelium; 

fastiDg. 


from  the  Dog,  while 


endosmoraeter,  together  witli  a  watery  alkaline  solution  of  similar 
strength,  it  was  found  that  the  oily  particles  penetrated  through  the 

animal    membrane    without 
^^S'  44.  much  difiiculty,  and  mingled 

with  the  fluid  on  the  opposite 
side.  Although,  therefore, 
we  cannot  explain  the  exact 
mechanism  of  absorption  in 
the  case  of  fat,  still  we  know 
that  it  is  not  in  opposition  to 
the  ordinary  phenomena  of 
endosmosis;  for  endosmosis 
will  take  place  with  a  fatty 
emulsion,  provided  the  fluids 
used  in  the  experiment  be 
slightly  alkaline  in  reaction. 
It  is,  accordingly,  by  a  pro- 
cess of  endosmosis,  or  imbi- 
bition, that  the  villi  take  up 
the  digested  fatty  substances.  There  are  no  open  orifices  or  canals, 
into  which  the  oil  penetrates ;  but  it  passes  directly  into  and  through 

the    substance  of    the  villi. 
^^'     '  The  epithelial  cells  covering 

the  external  surface  of  the 
villus  are  the  first  active 
agents  in  this  absorption.  In 
the  intervals  of  digestion  (Fig. 
44)  these  cells  are  but  slightly 
granular  and  nearly  trans- 
parent in  appearance.  But  if 
examined  during  the  diges- 
tion and  absorption  of  fat 
(Fig.  45),  their  substance  is 
seen  to  be  crowded  with  oily 
particles,  which  they  have 
taken  up  from  the  intestinal 
cavity  by  absorption.  The 
oily  matter  then  passes  on. 
ward,  penetrating  deeper  and  deeper  into  the  substance  of  the  villus, 
until  it  is  at  last  received  by  the  capillary  vessels  and  lacteals  in  its 
centre. 


Intestinal  Epithelium 
the  digestion  of  fat. 


from  the  Dog,  during 


ABSORPTION.  173 

The  fatty  substances  taken  up  by  the  portal  vein,  like  tbose  ab- 
sorbed by  tbe  lacteals,  do  not  at  once  enter  the  general  circulation, 
but  pass  first  through  the  capillary  system  of  the  liver.  Thence 
they  are  carried,  with  the  blood  of  the  hepatic  vein,  to  the  right 
side  of  the  heart,  and  subsequently  through  the  capillary  system  of 
the  lungs.  During  this  passage  they  become  altered  in  character, 
as  above  described,  and  lose  for  the  most  part  the  distinguishing 
characteristics  of  oily  matter,  before  they  have  passed  beyond  the 
pulmonary  circulation. 

But  as  digestion  proceeds,  an  increasing  quantity  of  fatty  matter 
finds  its  way,  by  these  two  passages,  into  the  blood ;  and  a  time  at 
last  arrives  when  the  whole  of  the  fat  so  introduced  is  not  destroyed 
during  its  passage  through  the  lungs.  Its  absorption  taking  place 
at  this  time  more  rapidly  than  its  decomposition,  it  begins  to  ap- 
pear, in  moderate  quantity,  in  the  blood  of  the  general  circulation; 
and,  lastly,  when  the  intestinal  absorption  is  at  its  point  of  greatest 
activity,  it  is  found  in  considerable  abundance  throughout  the 
entire  vascular  system.  At  this  period,  some  hours  after  the  inges- 
tion of  food  rich  in  oleaginous  matters,  the  blood  of  the  general 
circulation  everywhere  contains  a  superabundance  of  fat,  derived 
from  the  digestive  process.  If  blood  be  then  drawn  from  the  veins 
or  arteries  in  any  part  of  the  body,  it  will  present  the  peculiar 
appearance  known  as  that  of  "  chylous"  or  "  milky"  blood.  After 
the  separation  of  the  clot,  the  serum  presents  a  turbid  appearance ; 
and  the  fatty  substances,  which  it  contains,  rise  to  the  top  after  a 
few  hours,  and  cover  its  surface  with  a  partially  opaque  and  creamy- 
looking  pellicle.  This  appearance  has  been  occasionally  observed 
in  the  human  subject,  particularly  in  bleeding  for  apoplectic  attacks 
occurring  after  a  full  meal,  and  has  been  mistaken,  in  some  instances, 
for  a  morbid  phenomenon.  It  is,  however,  a  perfectly  natural  one, 
and  depends  simply  on  the  rapid  absorption,  at  certain  periods  of 
digestion,  of  oleaginous  substances  from  the  intestine.  It  can  be 
produced  at  will,  at  any  time,  in  the  dog,  by  feeding  him  with  fat 
meat,  and  drawing  blood,  seven  or  eight  hours  afterward,  from  the 
carotid  artery  or  the  jugular  vein. 

This  state  of  things  continues  for  a  varying  length  of  time,  ac- 
cording to  the  amount  of  oleaginous  matters  contained  in  the  food. 
When  digestion  is  terminated,  and  the  fat  ceases  to  be  introduced 
in  unusual  quantity  into  the  circulation,  its  transformation  and 
decomposition  continuing  to  take  place  in  the  blood,  it  disappears 
gradually  from  the  veins,  arteries,  and  capillaries  of  the  general 


174  ABSORPTION.  . 

system ;  and,  finally,  when  the  whole  of  the  fat  has  been  disposed 
of  by  the  nutritive  processes,  the  serum  again  becomes  transparent, 
and  the  blood  returns  to  its  ordinary  condition. 

In  this  manner  the  nutritive  elements  of  the  food,  prepared  for 
absorption  by  the  digestive  process,  are  taken  up  into  the  circulation 
under  the  different  forms  of  albuminose,  sugar,  and  chyle,  and  accu- 
mulate as  such,  at  certain  times,  in  the  blood.  But  these  conditions 
are  only  temporary,  or  transitional.  The  nutritive  materials  soon 
pass,  by  catalytic  transformation,  into  other  forms,  and  become 
assimilated  to  the  pre-existing  elements  of  the  circulating  fluid. 
Thus  they  accomplish  finally  the  whole  object  of  digestion ;  which 
is  to  replenish  the  blood  by  a  supply  of  new  materials  from  without. 
There  are,  however,  two  other  intermediate  processes,  taking  place 
partly  in  the  liver  and  partly  in  the  intestine,  at  about  the  same 
time,  and  having  for  their  object  the  final  preparation  and  perfec- 
tion of  the  circulating  fluid.  These  two  processes  require  to  be 
studied,  before  we  can  pass  on  to  the  particular  description  of  the 
blood  itself.  They  are :  1st,  the  secretion  and  reabsorption  of  the 
bile ;  and  2d,  the  production  of  sugar  in  the  liver,  and  its  subse- 
quent decomposition  in  the  blood. 


THE    BILE.  175 


CHAPTER    VIII. 

THE   BILE. 

The  bile  is  more  easily  obtained  in  a  state  of  purity  than  any 
otlier  of  tbe  secretions  whicli  find  their  way  into  tbe  intestinal 
canal,  owing  to  the  existence  of  a  gall-bladder  in  which  it  accn- 
mulates,  and  from  which  it  may  be  readily  obtained  without  any 
other  admixture  than  the  mucus  of  the  gall-bladder  itself.  Not- 
withstanding this,  its  study  has  proved  an  unusually  difficult  one. 
This  difficulty  has  resulted  from  the  peculiar  nature  of  the  biliary 
ingredients,  and  the  readiness  with  which  they  become  altered  by 
chemical  manipulation ;  and  it  is,  accordingly,  only  quite  recently 
that  we  have  arrived  at  a  correct  idea  of  its  real  constitution. 

The  bile,  as  it  comes  from  the  gall-bladder,  is  a  somewhat  viscid 
and  glutinous  fluid,  varying  in  color  and  specific  gravity  according 
to  the  species  of  animal  from  which  it  is  obtained.  Human  bile  is 
of  a  dark  golden  brown  color,  ox  bile  of  a  greenish  yellow,  pig's 
bile  of  a  nearly  clear  yellow,  and  dog's  bile  of  a  deep  brown.  We 
have  found  the  specific  gravity  of  human  bile  to  be  1018,  that  of 
ox  bile  1024,  that  of  pig's  bile  1030  to  1036.  The  reaction  of  the 
bile  with  test-paper  cannot  easily  be  determined ;  since  it  has  only 
a  bleaching  or  decolorizing  effect  on  litmus,  and  does  not  turn  it 
either  blue  or  red.  It  is  probably  either  neutral  or  very  slightly 
alkaline.  A  very  characteristic  physical  property  of  the  bile  is 
that  of  frothing  up  into  a  soap -like  foam  when  shaken  in  a  test- 
tube,  or  when  air  is  forcibly  blown  into  it  through  a  small  glass 
tube  or  blowpipe.  The  bubbles  of  foam,  thus  produced,  remain 
for  a  long  time  without  breaking,  and  adhere  closely  to  each  other 
and  to  the  sides  of  the  glass  vessel. 

The  following  is  an  analysis  of  the  bile  of  the  ox,  based  on  the 
calculations  of  Berzelius,  Frerichs,  and  Lehmann : — 


176  THE    BILE. 

Composition  of  Ox  Bilk. 

Water 888.00 

Gljko-cholate  of  soda 1       qo  00 

Tauro-cholate  "     " i 

Biliverdine 

Fats 

Oleates,  margarates,  and  stearates  of  soda  and  potassa 

Cholesterin J 

Chloride  of  sodium 

Phosphate  of  soda         ........ 

"  "  lime 1-       15.24 

"  "  magnesia         ....... 

Carbonates  of  soda  and  potassa 

Mucus  of  the  gall-bladder 1,34 


13.42 


1000.00 

Biliverdine. — Of  the  above  mentioned  ingredients,  hiliverdine 
is  peculiar  to  the  bile,  and  therefore  important,  though  not  pre- 
sent in  large  quantity.  This  is  the  coloring  matter  of  the  bile. 
It  is,  like  the  other  coloring  matters,  an  uncrystallizable  organic 
substance,  containing  nitrogen,  and  yielding  to  ultimate  analysis  a 
small  quantity  of  iron.  It  exists  in  such  small  quantity  in  the  bile 
that  its  exact  proportion  has  never  been  determined.  It  is  formed, 
so  far  as  can  be  ascertained,  in  the  substance  of  the  liver,  and  does 
not  pre-exist  in  the  blood.  It  may,  however,  be  reabsorbed  in 
cases  of  biliary  obstruction,  when  it  circulates  with  the  blood  and 
stains  nearly  all  the  tissues  and  fluids  of  the  body,  of  a  peculiar 
lemon  yellow  color.  This  is  the  symptom  which  is  characteristic 
of  jaundice. 

Cholesterin  (C25H22O). — This  is  a  crystallizable  substance  which 
resembles  the  fats  in  many  respects ;  since  it  is  destitute  of  nitrogen, 
readily  inflammable,  soluble  in  alcohol  and  ether,  and  entirely  in- 
soluble in  water.  It  is  not  saponifiable,  however,  by  the  action  of 
the  alkalies,  and  is  distinguished  on  this  account  from  the  ordinary 
fatty  substances.  It  occurs,  in  a  crystalline  form,  mixed  with  color- 
ing matter,  as  an  abundant  ingredient  in  most  biliary  calculi ;  and 
is  found  also  in  different  regions  of  the  body,  forming  a  part  of 
various  morbid  deposits.  "We  have  met  with  it  in  the  fluid  of 
hydrocele,  and  in  the  interior  of  many  encysted  tumors.  The 
crystals  of  cholesterin  (Fig.  46)  have  the  form  of  very  thin,  color- 
less, transparent,  rhomboidal  plates,  portions  of  which  are  often 
cut  out  by  lines  of  cleavage  parallel  to  the  sides  of  the  crystal. 
They  frequently  occur  deposited  in  layers,  in  which  the  outlines  of 


THE    BILE. 


177 


the  subjacent  crystals  show  very  distinctly  through  the  substance 


Cholesterin  is  not  formed  in  the 


Fig.  46. 


Cholestekin,  from  an  Encysted  Tumor- 


of  those  which  are  placed  above 
liver,  but  originates  in  the 
substance  of  the  brain  and 
nervous  tissue,  from  which 
it  may  be  extracted  in  large 
quantity  by  the  action  of 
alcohol.  It  has  also  been 
found,  by  Dr.  W.  Marcet,'  to 
exist,  in  considerable  abund- 
ance, in  the  tissue  of  the 
sjoleen.  From  all  these  tis- 
sues it  is  absorbed  by  the 
blood,  then  conveyed  to  the 
liver,  and  discharged  with 
the  bile. 


This  fact   has  been  fully 
confirmed  by  the  researches 

of  Prof.  A.  Flint,  Jr.,'  who  has  found  that  there  is  nearly  one-quarter 
part  more  cholesterin  in  the  blood  of  the  jugular  vein,  returning 
from  the  brain,  than  in  that  of  the  carotid  artery,  before  its  passage 
through  that  organ ;  and  that,  on  the  other  hand,  the  blood  of  the 
hepatic  artery,  as  well  as  that  of  the  portal  vein,  loses  cholesterin 
in  passing  through  the  liver,  so  that  but  a  small  quantity  can  be 
found  in  the  blood  of  the  hepatic  vein. 

The  cholesterin,  however,  after  being  poured  into  the  intestine 
with  the  bile,  is  decomposed  or  transformed  into  some  other  sub- 
stance, since  it  is  not  discharged  with  the  feces.^  Its  decomposition 
is  probably  effected  by  the  contact  of  the  intestinal  fluids. 

Biliary  Salts. — By  far  the  most  important  and  characteristic 
ingredients  of  this  secretion  are  the  two  saline  substances  mentioned 
above  as  the  glyko-cholate  and  tauro-cholate  of  soda.  These  sub- 
stances were  first  discovered  by  Strecker,  in  1848,  in  the  bile  of  the 
ox.  They  are  both  freely  soluble  in  water  and  in  alcohol,  but  in- 
soluble in  ether.     One  of  them,  the  tauro-cholate,  has  the  property^ 

'  In  American  Joum.  Med.  Sci.,  January,  1858. 

2  American  Joum.  Med.  Sci.,  October,  1862. 

3  Prof.  A.  Flint,  Jr.,  in  Am.  Joum.  Med.  Sci.,  Oct.  1862. 

12 


178 


THE    BILE. 


■when  itself  in  solution  in  water,  of  dissolving  a  certain  quantity  of 
fat ;  and  it  is  probably  owing  to  this  circumstance  that  some  free 
fat  is  present  in  the  bile.  The  two  biliary  substances  are  obtained 
from  ox  bile  in  the  following  manner : — 

The  bile  is  first  evaporated  to  dryness  by  the  water-bath.  The 
dry  residue  is  then  pulverized  and  treated  with  absolute  alcohol,  in 
the  proportion  of  at  least  5j  of  alcohol  to  every  five  grains  of  dry 
residue.  The  filtered  alcoholic  solution  has  a  clear  yellowish  color. 
It  contains,  beside  the  glyko-cholate  and  tauro-cholate  of  soda,  the 
coloring  matter  and  more  or  less  of  the  fats  originally  present  in 
the  bile.  On  the  addition  of  a  small  quantity  of  ether,  a  dense, 
whitish  precipitate  is  formed,  which  disappears  again  on  agitating 
and  thoroughly  mixing  the  fluids.  On  the  repeated  addition  of 
ether,  the  precipitate  again  falls  down,  and  when  the  ether  has  been 
added  in  considerable  excess,  six  to  twelve  times  the  volume  of  the 
alcoholic  solution,  the  precipitate  remains  permanent,  and  the  whole 
mixture  is  filled  with  a  dense,  whitish,  opaque  deposit,  consisting 
of  the  glyko-cholate  and  tauro-cholate  of  soda,  thrown  down  under 
the  form  of  heavy  flakes  and  granules,  part  of  which  subside  to 


Fig.  47. 


Fig.  48. 


Ox-bile,  extracted  with  absolute 
alcohol  and  precipitated  with  ether. 


Gr.TKO-rnoLATE  of  Soda  from  Ox-btle, 
after  two  days'  crystallization.  At  the  lower  part  of 
the  fiuiire  the  crystals  are  melting  into  drops,  from  the 
evaporation  of  the  ether  and  absorption  of  moisture. 


the  bottom  of  the  test-tube,  while  part  remain  for  a  time  in  suspen- 
sion. Gradually  these  flakes  and  granules  unite  with  each  other 
and  fuse  together   into   clear,  brownish-yellow,  oily,  or  resinous- 


THE    BILE. 


179 


looking  drops.  At  the  bottom  of  the  test-tube,  after  two  or  three 
hours,  there  is  usually  collected  a  nearly  homogeneous  layer  of 
this  deposit,  while  the  remainder  continues  to  adhere  to  the  sides 
of  the  glass  in  small,  circular,  transparent  drops.  The  deposit  is 
semi-fluid  in  consistency,  and  sticky,  like  Canada  balsam  or  half- 
melted  resin ;  and  it  is  on  this  account  that  the  ingredients  compos- 
ing it  have  been  called  the  "  resinous  matters"  of  the  bile.  They 
have,  however,  no  real  chemical  relation  with  true  resinous  bodies, 
since  they  both  contain  nitrogen,  and  differ  from  resins  also  in 
other  important  particulars. 

At  the  end  of  twelve  to  twenty-four  hours,  the  glyko-cholate  of 
soda  begins  to  crystallize.  The  cr3^stals  radiate  from  various  points 
in  the  resinous  deposit,  and  shoot  upward  into  the  supernatant 
fluid,  in  white,  silky  bundles.  (Fig.  47.)  If  some  of  these  crystals 
be  removed  and  examined  by  the  microscope,  they  are  found  to  be 
of  a  very  delicate  acicular  form,  running  to  a  finely  pointed 
extremity,  and  radiating,  as  already  mentioned,  from  a  central 
point.  (Fig.  48.)  As  the  ether  evaporates,  the  crystals  absorb 
moisture  from  the  air,  and  melt  up  rapidly  into  clear  resinous 
drops ;  so  that  it  is  difficult  to  keep  them  under  the  microscope 
long  enough   for   a   correct 


drawing  and  measurement. 
The  crystallization  in  the 
test-tube  goes  on  after  the 
first  day,  and  the  crystals  in- 
crease in  quantity  for  three 
or  four,  or  even  five  or  six 
days,  until  the  whole  of  the 
glyko  cholate  of  soda  present 
has  assumed  the  solid  form. 
The  tauro-cholate,  however, 
is  uncrystallizable,  and  re- 
mains in  an  amorphous  con- 
dition.    If  a  portion  of  the 


Fig.  49. 


deposit  be  now  removed  and 
examined  by  the  microscope, 


Gltko-oholate  and  Tafro-cholate  op 

Soda,   from  Ox-bile,  after  six  days'  cryKtalliza- 

•,     •  ^^      i   J.^  i.    1         r>     tion.     The   glyko-cholate  is  crj'stallized  ;   the  tauro- 

it  IS  seen  that  the  crystals  oi     ,,.,.„.,  , 

•/  chelate  is  m  fluid  drops. 

glyko-cholate  of  soda  have 

increased  considerably  in  thickness  (Fig.  49),  so  that  their  trans- 
verse diameter  may  be  readily  estimated.  The  uncrystallizable 
tauro-cholate  appears  under  the  form  of   circular  drops,  varying 


180  THE    BILE. 

considerably  in  size,  clear,  transparent,  strongly  refractive,  and 
bounded  by  a  dark,  well-defined  outline.  These  drops  are  not  to  he 
distinguished,  hy  any  of  their  optical  properties,  from  oil- globules,  as 
they  usually  appear  under  the  microscope.  They  have  the  same 
refractive  power,  the  same  dark  outline  and  bright  centre,  and  the 
same  degree  of  consistency.  They  would  consequently  be  liable  at 
all  times  to  be  mistaken  for  oil-globules,  were  it  not  for  the  complete 
dissimilarity  of  their  chemical  properties. 

Both  the  glyko-cholate  and  tauro-cholate  of  soda  are  very  freely 
soluble  in  water.  If  the  mixture  of  alcohol  and  ether  be  poured 
off  and  distilled  water  added,  the  deposit  dissolves  rapidly  and 
completely,  with  a  more  or  less  distinct  yellowish  color,  according 
to  the  proportion  of  coloring  matter  originally  present  in  the  bile. 
The  two  biliary  substances  present  in  the  watery  solution  may  be 
separated  from  each  other  by  the  following  means.  On  the  addi- 
tion of  acetate  of  lead,  the  glyko-cholate  of  soda  is  decomposed, 
and  precipitates  as  a  glyko-cholate  of  lead.  The  precipitate,  sepa- 
rated by  filtration  from  the  remaining  fluid,  is  then  decomposed  in 
turn  by  carbonate  of  soda,  and  the  original  glyko-cholate  of  soda 
reproduced.  The  filtered  fluid  which  remains,  and  which  contains 
the  tauro-cholate  of  soda,  is  then  treated  with  suhacetate  of  had, 
which  precipitates  a  tauro-cholate  of  lead.  This  is  separated  by 
filtration,  washed,  and  decomposed  again  by  carbonate  of  soda,  as 
in  the  former  case. 

The  two  biliary  substances  in  ox  bile  may,  therefore,  be  dis- 
tinguished by  their  reactions  with  the  salts  of  lead.  Both  are 
precipitable  by  the  subacetate ;  but  the  glyko-cholate  of  soda  is 
precipitable  also  by  the  acetate,  while  the  tauro-cholate  is  not  so. 
If  subacetate  of  lead,  therefore,  be  added  to  the  mixed  watery  solu- 
tion of  the  two  substances,  and  the  whole  filtered,  the  subsequent 
addition  of  acetate  of  lead  to  the  filtered  fluid  will  produce  no  pre- 
cipitate, because  both  the  biliary  matters  have  been  entirely  thrown 
down  with  the  deposit ;  but  if  the  acetate  of  lead  be  first  added,  it 
will  precipitate  the  glyko-cholate  alone,  and  the  tauro-cholate  may 
afterward  be  thrown  down  separately  by  the  subacetate. 

These  two  substances,  examined  separately,  have  been  found  to 
possess  the  following  properties : — 

Glyko-cholate  of  soda  (NaO,Cj2H42^0„)  crystallizes,  when  precipi- 
tated by  ether  from  its  alcoholic  solution,  in  radiating  bundles  of 
fine  white  silky  needles,  as  above  described.  It  is  composed  of 
soda,  united  with  a  peculiar  acid  of  organic  origin,  viz.,  glyho-cholic 


THE    BILE.  181 

acid  (Cj2H42NOii,HO).  This  acid  is  crystallizable  and  contains  nitro- 
gen, as  shown  by  the  above  formula,  which  is  that  given  by  Leh- 
mann.  If  boiled  for  a  long  time  with  a  dilute  solution  of  potassa, 
glyko-cholic  acid  is  decomposed  with  the  production  of  two  new 
substances;  the  first  a  non-nitrogenous  acid  body,  cholic  acid 
(C48H390g,HO) ;  the  second  a  nitrogenous  neutral  body,  glycine 
(C4H3NOJ.  Hence  the  name  glyko-cholic  acid,  given  to  the 
original  substance,  as  if  it  were  a  combination  of  cholic  acid  with 
glycine.  In  reality,  however,  these  two  substances  do  not  exist 
originally  in  the  glyko-cholic  acid,  but  are  rather  new  combinations 
of  its  elements,  produced  by  long  boiling,  in  contact  with  potassa 
and  water.  They  are  not,  therefore,  to  be  regarded  as,  in  any  way, 
natural  ingredients  of  the  bile,  and  do  not  throw  any  light  on  the 
real  constitution  of  glyko-cholic  acid. 

Tauro-cholate  of  soda  Q^aOjQ^^^^'&^O^^  is  also  a  very  abundant 
ingredient  of  the  bile.  It  is  said  by  Eobin  and  Verdeil'  that  it  is 
not  crystallizable,  owing  probably  to  its  not  having  been  separated 
as  yet  in  a  perfectly  pure  condition.  Lehmann  states,  on  the  con- 
trary, that  it  may  crystallize,^  when  kept  for  a  long  time  in  contact 
with  ether.  "We  have  not  been  able  to  obtain  this  substance,  how- 
ever, in  a  crystalline  form.  Its  acid  constituent,  tauro-cholic  acid, 
is  a  nitrogenous  body,  like  glyko-cholic  acid,  but  differs  from  the 
latter  by  containing  in  addition  two  equivalents  of  sulphur.  By 
long  boiling  in  a  dilute  solution  of  potassa,  it  is  decomposed  with 
the  production  of  two  other  substances ;  the  first  of  them  the  same 
acid  body  mentioned  above  as  derived  from  the  glyko-cholic,  viz., 
cholic  acid;  and  the  second  a  new  nitrogenous  neutral  body,  viz., 
taurine  (C^H^NS^Og).  The  same  remark  holds  good  with  regard  to 
these  two  bodies,  that  we  have  already  made  in  respect  to  the  sup- 
posed constituents  of  glyko-cholic  acid.  Neither  cholic  acid  nor 
taurine  can  be  properly  regarded  as  really  ingredients  of  tauro- 
cholic  acid,  but  only  as  artificial  products  resulting  from  its  altera- 
tion and  decomposition. 

The  glyko-cholates  and  tauro-cholates  are  formed,  so  far  as  we 
know,  exclusively  in  the  liver ;  since  they  have  not  been  found  in 
the  blood,  nor  in  any  other  part  of  the  body,  in  healthy  animals ; 
nor  even,  in  the  experiments  of  Kunde,  Moleschott,  and  Lehmann 
on  frogs,^  after  the  entire  extirpation  of  the  liver,  and  consequent 

'  Chimie  Anatomique  et  Physiologique,  vol.  ii.  p.  473. 

^  Physiological  Chemistry,  Phil,  ed.,  vol.  i.  p.  209. 

*  Lehmann's  Physiological  Chemistry,  Phil,  ed.,  vol.  i.  p.  47G. 


182 


THE    BILE. 


Fis.  50. 


suppression  of  the  bile.  These  substances  are,  therefore,  produced 
in  the  glandular  cells  of  the  liver,  by  transformation  of  some  other 
of  their  ingredients.  They  are  then  exuded  in  a  soluble  form,  as 
part  of  the  bile,  and  finally  discharged  by  the  excretory  hepatic 
ducts. 

The  two  substances  described  above  as  the  tauro-cholate  and 
glyko-cholate  of  soda  exist,  properly  speaking,  only  in  the  bile  of 
the  ox,  where  they  were  first  discovered  by  Strecker.  In  examin- 
ing the  biliary  secretions  of  difierent  species  of  animals,  Strecker 
found  so  great  a  resemblance  between  them,  that  he  was  disposed 
to  regard  their  ingredients  as  essentially  the  same.  Having  estab- 
lished the  existence  in  ox-bile  of  two  peculiar  substances,  one 
crystallizable  and  non-sulphurous  (glyko-cholate),  the  other  uncrys- 
tallizable  and  sulphurous  (tauro-cholate),  he  was  led  to  consider 
the  bile  in  all  species  of  animals  as  containing  the  same  siibstances, 
and  as  differing  only  in  the  relative  quantity  in  which  the  two 
were  present.  The  only  exception  to  this  was 
supposed  to  be  pig's  bile,  in  which  Strecker  found 
a  peculiar  organic  acid,  the  "hyo-cholic"  or 
''  hyo-cholinic"  acid,  in  combination  with  soda  as 
a  base. 

The  above  conclusion  of  his,  however,  was  not 
entirely  correct.  It  is  true  that  the  bile  of  all 
animals,  so  far  as  examined,  contains  peculiar 
substances,  which  resemble  each  other  in  being 
freely  soluble  in  water,  soluble  in  absolute  alco- 
hol, and  insoluble  in  ether  ;  and  in  giving  also  a 
peculiar  reaction  with  Pettenkofer's  test,  to  be 
described  presently.  But,  at  the  same  time,  these 
substances  present  certain  minor  differences  in 
different  animals,  which  show  them  not  to  be 
identical. 

In  dog's  bile,  for  example,  there  are,  as  in  ox- 
bile,  two  substances  precipitable  by  ether  from 
their  alcoholic  solution;  one  crystallizable,  the 
other  not  so.  But  the  former  of  these  substances 
crystallizes  much  more  readily  than  the  glyko- 
cholate  of  soda  from  ox-bile.  Dog's  bile  will  not  unfrequently  begin 
to  crystallize  freely  in  five  to  six  hours  after  precipitation  by  ether 
(Fig.  50) ;  while  in  ox-bile  it  is  usually  twelve,  and  often  twenty- 
four  or  even  forty-eight  hours  before  crystallization  is  fully  estab- 


Doo'sBiLE,  extract- 
ed with  absolute  alcohol 
and  precipitated  with 
ether. 


THE    BILE. 


183 


Fig.  51. 


lisKed.  But  it  is  more  particularly  in  their  reaction  with  the  salts 
of  lead  that  the  difference  between  these  substances  becomes  mani- 
fest. For  while  the  crjstallizable  substance  of  ox-bile  is  precipi- 
tated bj  acetate  of  lead,  that  of  dog's  bile  is  not  affected  by  it.  If 
dog's  bile  be  evaporated  to  dryness,  extracted  with  absolute  alcohol, 
the  alcoholic  solution  precipitated  by  ether,  and  the  ether  precipitate 
then  dissolved  in  water,  the  addition  of  acetate  of  lead  to  the  watery 
solution  produces  not  the  slighest  turbidity.  If  subacetate  of  lead 
be  then  added  in  excess,  a  copious  precipitate  falls,  composed  of  both 
the  crystallizable  and  uncrystallizable  substances.  If  the  lead  pre- 
cipitate be  then  separated  by  filtration,  washed,  and  decomposed, 
as  above  described,  by  carbonate  of  soda,  the  watery  solution  will 
contain  the  re-formed  soda  salts  of  the  bile.  The  watery  solution 
may  then  be  evaporated  to  dryness,  extracted  with  absolute  alcohol, 
and  the  alcoholic  solution  precipitated  by  ether ;  when  the  ether 
precipitate  crystallizes  partially  after  a  time  as  in  fresh  bile.  Both 
the  biliary  matters  of  dog's  bile  are  therefore 
precipitable  by  subacetate  of  lead,  but  neither  of 
them  by  the  acetate.  Instead  of  calling  them, 
consequently,  glyko-cholate  and  tauro  cholate  of 
soda,  we  shall  speak  of  them  simply  as  the  "  crys- 
talline" and  "resinous"  biliary  substances. 

In  cat's  bile,  the  biliary  substances  act  very 
much  as  in  dog's  bile.  The  ether  precipitate  of 
the  alcoholic  solution  contains  here  also  a  crys- 
talline and  a  resinous  substance ;  both  of  which 
are  precipitable  from  their  watery  solution  by 
subacetate  of  lead,  but  neither  of  them  by  the 
acetate. 

In  pig's  bile,  on  the  other  hand,  there  is  no 
crystallizable  substance,  but  the  ether  precipitate 
is  altogether  resinous  in  appearance.  Notwith- 
standing this,  its  watery  solution  precipitates 
abundantly  by  both  the  acetate  and  subacetate  of 
lead. 

In  human  bile,  again,  there  is  no  crystallizable 
substance.     "We  have  found  that  the  dried  bile, 
extracted  with  absolute  alcohol,  makes  a  clear,  brandy-red  solution, 
which  precipitates  abundantly  with  ether  in  excess ;  but  the  ether 
precipitate,  if  allowed  to  stand,  shows  no  sign  of  crystallization,  even 
at  the  end  of  three  weeks.     (Fig.  51.)     If  the- resinous  precipitate 


■ 

* 

■ 
'          1 

,_-- r^;^^ 

HuMAS  Bile,  ex- 
tracted with  absolute 
alcohol  and  precipitated 
by  ether. 


184  THE    BILE. 

be  separated  by  decantation  and  dissolved  in  water,  it  precipitates, 
as  in  the  case  of  pig's  bile,  by  both  the  acetate  and  subacetate  of 
lead.  This  might,  perhaps,  be  attributed  to  the  presence  of  two 
different  substances,  as  in  ox-bile,  one  precipitated  by  the  acetate, 
the  other  by  the  subacetate  of  lead.  Such,  however,  is  not  the  case. 
For  if  the  watery  solution  be  precipitated  by  the  acetate  of  lead 
and  then  filtered,  the  filtered  fluid  gives  no  precipitate  afterward 
by  the  subacetate ;  and  if  first  precipitated  by  the  subacetate  it 
gives  no  precipitate  after  filtration  by  the  acetate.  The  entire 
biliary  ingredients,  therefore,  of  human  bile  are  precipitated  by 
both  or  either  of  the  salts  of  lead. 

Different  kinds  of  bile  vary  also  in  other  respects ;  as,  for  ex- 
ample, their  specific  gravity,  the  depth  and  tinge  of  their  color,  the 
quantity  of  fat  which  they  contain,  &c.  &c.  We  have  already 
mentioned  the  variations  in  color  and  specific  gravity.  The  alco- 
holic solution  of  dried  ox-bile,  furthermore,  does  not  precipitate  at 
all  on  the  addition  of  water ;  while  that  of  human  bile,  of  pig's 
bile,  and  of  dog's  bile  precipitate  abundantly  with  distilled  water, 
owing  to  the  quantity  of  fat  which  they  hold  in  solution.  These 
variations,  however,  are  of  secondary  importance  compared  with 
those  which  we  have  already  mentioned,  and  which  show  that  the 
crystalline  and  resinous  substances  in  different  kinds  of  bile,  though 
resembling  each  other  in  very  many  respects,  are  yet  in  reality  far 
from  being  identical. 

Te^s  foe  Bile. — In  investigating  the  physiology  of  any  animal 
fluid  it  is,  of  course,  of  the  first  importance  to  have  a  convenient 
and  reliable  test  by  which  its  presence  may  be  detected.  For  a 
long  time  the  only  test  employed  in  the  case  of  bile,  was  that  which 
depended  on  a  change  of  color  produced  by  oxidizing  substances.  If 
the  bile,  for  example,  or  a  mixture  containing  bile,  be  exposed  in 
an  open  glass  vessel  for  a  few  hours,  the  upper  layers  of  the  fluid, 
which  are  in  contact  with  the  atmosphere,  gradually  assume  a 
greenish  tinge,  which  becomes  deeper  with  the  length  of  time  which 
elapses,  and  the  quantity  of  bile  existing  in  the  fluid.  Nitric  acid, 
added  to  a  mixture  of  bile  and  shaken  up,  produces  a  dense  preci- 
pitate which  takes  a  bright  grass-green  hue.  Tincture  of  iodine 
produces  the  same  change  of  color,  when  added  in  small  quantity ; 
and  probably  there  are  various  other  substances  which  would  have 
the  same  effect.  It  is  by  this  test  that  the  bile  has  so  often  been 
recognized  in  the  urine,  serous  effusions,  the  solid  tissues,  &c.,  in 


TESTS    FOR    BILE.  185 

cases  of  jaundice.  But  it  is  very  insufficient  for  anything  like 
accurate  investigation,  since  the  appearances  are  produced  simply 
by  the  action  of  an  oxidizing  agent  on  the  coloring  matter  of  the 
bile.  A  green  color  produced  by  nitric  acid  does  not,  therefore, 
indicate  the  presence  of  the  biliary  substances  proper,  but  only  of 
the  biliverdine.  On  the  other  hand,  if  the  coloring  matter  be  ab- 
sent, the  biliary  substances  themselves  cannot  be  detected  by  it. 
For  if  the  biliary  substances  of  dog's  bile  be  precipitated  by  ether 
from  an  alcoholic  solution,  dissolved  in  water  and  decolorized  by 
animal  charcoal,  the  colorless  watery  solution  will  then  give  no 
green  color  on  the  addition  of  nitric  acid  or  tincture  of  iodine, 
though  it  may  precipitate  abundantly  by  subacetate  of  lead,  and 
give  the  other  reactions  of  the  crystalline  and  resinous  biliary 
matters  in  a  perfectly  distinct  manner. 

Pettenhofer's  Test. — This  is  undoubtedly  the  best  test  yet  pro- 
posed for  the  detection  of  the  biliary  substances.  It  consists  in 
mixing  with  a  watery  solution  of  the  bile,  or  of  the  biliary  sub- 
stances, a  little  cane  sugar,  and  then  adding  sulphuric  acid  to  the 
mixture  until  a  red,  lake,  or  purple  color  is  produced.  A  solution 
may  be  made  of  cane  sugar,  in  the  proportion  of  one  part  of  sugar  to 
four  parts  of  water,  and  kept  for  use.  One  drop  of  this  solution  is 
mixed  with  the  suspected  fluid,  and  the  sulphuric  acid  then  imme- 
diately added.  On  first  dropping  in  the  sulphuric  acid,  a  whitish 
precipitate  falls,  which  is  abundant  in  the  case  of  ox-bile,  less  so  in 
that  of  the  dog.  This  precipitate  redissolves  in  a  slight  excess  of 
sulphuric  acid,  which  should  then  continue  to  be  added  until  the 
mixture  assumes  a  somewhat  syrupy  consistency  and  an  opalescent 
look,  owing  to  the  development  of  minute  bubbles  of  air.  A  red 
color  then  begins  to  show  itself  at  the  bottom  of  the  test-tube,  and 
afterward  spreads  through  the  mixture,  until  the  whole  fluid  is  of 
a  clear,  bright,  cherry  red.  This  color  gradually  changes  to  a  lake, 
and  finally  to  a  deep,  rich,  opaque  purple.  If  three  or  four  vol- 
umes of  water  be  then  added  to  the  mixture,  a  copious  precipitate 
falls  down,  and  the  color  is  destroyed. 

Various  circumstances  modify,  to  some  extent,  the  rapidity  and 
distinctness  with  which  the  above  changes  are  produced.  If  the 
biliary  substances  be  present  in  large  quantity,  and  nearly  pure, 
the  red  color  shows  itself  at  once  after  adding  an  equal  volume  of 
sulphuric  acid,  and  almost  immediately  passes  into  a  strong  purple. 
If  they  be  scanty,  on  the  other  hand,  the  red  color  may  not  show 
itself  for  seven  or  eight  minutes,  nor  the  purple  under  twenty 


186  THE    BILE. 

or  twenty-five  minutes.  If  foreign  matters,  again,  not  of  a  biliary 
nature,  be  also  present,  they  are  apt  to  be  acted  on  by  the  sulphuric 
acid,  and,  by  becoming  discolored,  interfere  with  the  clearness  and 
brilliancy  of  the  tinges  produced.  On  this  account  it  is  indispen- 
sable, in  delicate  examinations,  to  evaporate  the  suspected  fluid  to 
dryness,  extract  the  dry  residue  with  absolute  alcohol,  precipitate 
the  alcoholic  solution  with  ether,  and  dissolve  the  ether-precipitate 
in  water  before  applying  the  test.  In  this  manner,  all  foreign  sub- 
stances which  might  do  harm  will  be  eliminated,  and  the  test  will 
succeed  without  difficulty. 

It  must  not  be  forgotten,  furthermore,  that  the  sugar  itself  is 
liable  to  be  acted  on  and  discolored  by  sulphuric  acid  when  added 
in  excess,  and  may  therefore  by  itself  give  rise  to  confusion.  A  little 
care  and  practice,  however,  will  enable  the  experimenter  to  avoid 
all  chance  of  deception  from  this  source.  When  sulphuric  acid  is 
mixed  with  a  watery  solution  containing  cane  sugar,  after  it  has 
been  added  in  considerable  excess,  a  yellowish  color  begins  to  show 
itself,  owing  to  the  commencing  decomposition  of  the  sugar.  This 
color  gradually  deepens  until  it  has  become  a  dark,  dingy,  muddy 
brown ;  but  there  is  never  at  any  time  any  clear  red  or  purple 
color,  unless  biliary  matters  be  present.  If  the  bile  be  present  in 
but  small  quantity,  the  colors  produced  by  it  may  be  modified  and 
obscured  by  the  dingy  yellow  and  brown  of  the  sugar ;  but  even 
this  difficulty  may  be  avoided  by  paying  attention  to  the  following 
precautions.  In  the  first  place,  only  very  little  sugar  should  be 
added  to  the  suspected  fluid.  In  the  second  place,  the  sulphuric 
acid  should  be  added  very  gradually,  and  the  mixture  closely 
watched  to  detect  the  first  changes  of  color.  If  bile  be  present,  the 
red  color  peculiar  to  it  is  always  produced  before  the  yellowish 
tinge  which  indicates  the  decomposition  of  the  sugar.  When  the 
biliary  matters,  therefore,  are  present  in  small  quantity,  the  addi- 
tion of  sulphuric  acid  should  be  stopped  at  that  point,  and  the 
colors,  though  faint,  will  then  remain  clear,  and  give  unmistakable 
evidence  of  the  presence  of  bile. 

The  red  color  alone  is  not  sufficient  as  an  indication  of  bile.  It 
is  in  fact  only  the  commencement  of  the  change  which  indicates  the 
biliary  matters.  If  these  matters  be  present,  the  color  passes,  as 
we  have  already  mentioned,  first  into  a  lake,  then  into  a  purple ; 
and  it  is  this  lake  and  purple  color  alone  which  can  be  regarded  as 
really  characteristic  of  the  biliary  reaction. 

It  is  important  to  observe  that  Pettenkofer's  reaction  is  produced 


TESTS    FOR    BILE.  187 

by  tlie  presence  of  either  or  both  of  the  biliary  substances  proper ; 
and  is  not  at  all  dependent  on  the  coloring  matter  of  the  bile.  For 
if  the  two  biliary  substances,  crystalline  and  resinous,  be  extracted 
by  the  process  above  described,  and,  after  being  dissolved  in  water, 
decolorized  with  animal  charcoal,  the  watery  solution  will  still  give 
Pettenkofer's  reaction  perfectly,  though  no  coloring. matter  be  pre- 
sent, and  though  no  green  tinge  can  be  produced  by  the  addition 
of  nitric  acid  or  tincture  of  iodine.  If  the  two  biliary  substances 
be  then  separated  from  each  other,  and  tested  in  distinct  solutions, 
each  solution  will  give  the  same  reaction  promptly  and  completely. 

Yarious  objections  have  been  urged  against  this  test.  It  has 
been  stated  to  be  uncertain  and  variable  in  its  action.  Eobin  and 
Verdeil'  say  that  its  reactions  "do  not  belong  exclusively  to  the 
bile,  and  may  therefore  give  rise  to  mistakes."  Some  fatty  sub- 
stances and  volatile  oils  (oleine,  oleic  acid,  oil  of  turpentine,  oil  of 
caraway)  have  been  stated  to  produce  similar  red  and  violet  colors, 
when  treated  with  sugar  and  sulphuric  acid.  These  objections, 
however,  have  not  much,  if  any,  practical  weight.  The  test  no 
doubt  requires  some  care  and  practice  in  its  application,  as  we  have 
already  pointed  out ;  but  this  is  the  case  also,  to  a  greater  or  less 
extent,  with  nearly  all  chemical  tests,  and  particularly  with  those 
for  substances  of  organic  origin.  No  other  substance  is,  in  point 
of  fact,  liable  to  be  met  with  in  the  intestinal  fluids  or  the  blood, 
which  would  simulate  the  reactions  of  the  biliary  matters.  We 
have  found  that  the  fatty  matters  of  the  chyle,  taken  from  the  thO'- 
racic  duct,  do  not  give  any  coloration  which  would  be  mistaken  for 
that  of  the  bile.  When  the  volatile  oils  (caraway  and  turpentine) 
are  acted  on  by  sulphuric  acid,  a  red  color  is  produced  which  after- 
ward becomes  brown  and  blackish,  and  a  peculiar,  tarry,  empyreu- 
matic  odor  is  developed  at  the  same  time ;  but  we  do  not  get  the 
lake  and  purple  colors  spoken  of  above.  Finally,  if  the  precaution 
be  observed — first  of  extracting  the  suspected  matters  with  absolute 
alcohol,  then  precipitating  with  ether  and  dissolving  the  precipitate 
in  water,  no  ambiguity  could  result  from  the  presence  of  any  of  the 
above  substances. 

Pettenkofer's  test,  then,  if  used  with  care,  is  extremely  useful, 
and  may  lead  to  many  valuable  results.  Indeed,  no  other  test  than 
this  can  be  at  all  relied  on  to  determine  the  presence  or  absence  of 
the  biliary  substances  proper. 

'  Op.  cit.,  vol.  ii.  p.  468. 


188  THE    BILE. 

Variations  and  Functions  of  Bile. — Witli  regard  to  the 
entire  quantity  of  bile  secreted  daily,  we  have  had  no  very  positive 
knowledge,  until  the  experiments  of  Bidder  and  Schmidt,  published 
in  1852.^  These  experiments  were  performed  on  cats,  dogs,  sheep, 
and  rabbits,  in  the  following  manner.  The  abdomen  was  opened, 
and  a  ligature  placed  upon  the  ductus  communis  choledochus,  so 
as  to  prevent  the  bile  finding  its  way  into  the  intestine.  An  open- 
ing was  then  made  in  the  fundus  of  the  gall-bladder,  by  which 
the  bile  was  discharged  externally.  The  bile,  so  discharged,  was 
received  into  previously  weighed  vessels,  and  its  quantity  accurately 
determined.  Each  observation  usually  occupied  about  two  hours, 
during  which  period  the  temporary  fluctuations  occasionally  observ- 
able in  the  quantity  of  bile  discharged  were  mutually  corrected,  so 
far  as  the  entire  result  was  concerned.  The  animal  was  then  killed, 
weighed,  and  carefully  examined,  in  order  to  make  sure  that  the 
biliary  duct  had  been  securely  tied,  and  that  no  inflammatory  alter- 
ation had  taken  place  in  the  abdominal  organs.  The  observations 
were  made  at  very  diflerent  periods  after  the  last  meal,  so  as  to 
determine  the  influence  exerted  by  the  digestive  process  upon  the 
rapidity  of  the  secretion.  The  average  quantity  of  bile  for  twenty- 
four  hours  was  then  calculated  from  a  comparison  of  the  above 
results ;  and  the  quantity  of  its  solid  ingredients  was  also  ascer- 
tained in  each  instance  by  evaporating  a  portion  of  the  bile  in  the 
water  bath,  and  weighing  the  dry  residue. 

Bidder  and  Schmidt  found  in  this  way  that  the  daily  quantity 
of  bile  varied  considerably  in  different  species  of  animals.  It  was 
very  much  greater  in  the  herbivorous  animals  used  for  experiment 
than  in  the  carnivora.  The  results  obtained  by  these  observers 
are  as  follows : — 

For  every  pound  weight  of  the  entire  body  there  is  secreted 

during  twenty-four  hours 

Fresh  Bile.  Dry  Residde. 

In  the  cat        ......     102  grains.  5.712  grains. 

•'dog 140     "  6.916     " 

»      sheep 178     "  9.408     " 

"      rabbit 9.'i8     "  17.290     " 

Since,  in  the  human  subject,  the  digestive  processes  and  the 
nutritive  actions  generally  resemble  those  of  the  carnivora,  rather 
than  those  of  the  herbivora,  it  is  probable  that  the  daily  quantity 
of  bile  in  man  is  very  similar  to  that  in  the  carnivorous  animals. 

'  Verdaungssaefte  und  Stoffwechsel.     Leipzig,  1852. 


VARIATIONS    AND    FUNCTIONS    OF    BILE. 


189 


If  we  apply  to  the  human  subject  the  average  results  obtained  by 
Bidder  and  Schmidt  from  the  cat  and  dog,  we  find  that,  in  an  adult 
man,  weighing  140  pounds,  the  daily  quantity  of  the  bile  will  be 
certainly  not  less  than  16,940  grains,  or  very  nearly  2|  pounds 
avoirdupois. 

It  is  a  matter  of  great  importance,  in  regard  to  the  bile,  as  well 
as  the  other  intestinal  fluids,  to  ascertain  whether  it  be  a  constant 
secretion,  like  the  urine  and  perspiration,  or  whether  it  be  intermit- 
tent, like  the  gastric  j  uice,  and  discharged  only  during  the  digestive 
process.  In  order  to  determine  this  point,  we  have  performed  the 
following  series  of  experiments  on  dogs.  The  animals  were  kept 
confined,  and  killed  at  various  periods  after  feeding,  sometimes  by 
the  inoculation  of  woorara,  sometimes  i  by  hydrocyanic  acid,  but 
most  frequently  by  section  of  the  medulla  oblongata.  The  con- 
tents of  the  intestine  were  then  collected  and  examined.  In  all 
instances,  the  bile  was  also  taken  from  the  gall-bladder,  and  treated 
in  the  same  way,  for  purposes  of  comparison.  The  intestinal  con- 
tents always  presented  some  peculiarities  of  appearance  when  treated 
with  alcohol  and  ether,  owing  probably  to  the  presence  of  other 
substances  than  the  bile ;  but  they  always  gave  evidence  of  the 
presence  of  biliary  matters 
as  well.  The  biliary  sub- 
stances could  almost  always 
be  recognized  by  the  mi- 
croscope in  the  ether  preci- 
pitate of  the  alcoholic  solu- 
tion ;  the  resinous  substance, 
under  the  form  of  rounded, 
oily-looking  drops  (Fig.  52), 
and  the  other,  under  the 
form  of  crystalline  groups, 
generally  presenting  the 
appearance  of  double  bun- 
dles of  slender,  radiating, 
slightly  curved  or  wavy, 
needle  -  shaped  crystals. 
These  substances,  dissolved 
in  water,  gave  a  purple 
color  with  sugar  and  sulphuric  acid.  These  experiments  were 
tried  after  the  animals  had  been  kept  for  one,  two,  three,  five,  six, 
seven,  eight,  and  twelve  days  without  food.     The  result  showed  that, 


Crystalline  ant>  Resinous  Biliary  Sru- 
STANCEs;  from  Small  Intestine  of  Dog,  after  two  days 
fasting. 


190 


THE    BILE. 


in  all  these  instances,  bile  was  present  in  the  small  intestine.  It  is, 
therefore,  plainly  not  an  intermittent  secretion,  nor  one  which  is 
concerned  exclusively  in  the  digestive  process ;  but  its  secretion  is 
constant,  and  it  continues  to  be  discharged  into  the  intestine  for 
many  dg-ys  after  the  animal  has  been  deprived  of  food. 

The  next  point  of  importance  to  be  examined  relates  to  the  time 
after  feeding  at  which  the  bile  passes  into  the  intestine  in  the  greatest 
ahundayice.  Bidder  and  Schmidt  have  already  investigated  this 
point  in  the  following  manner.  They  operated,  as  above  described, 
by  tying  the  common  bile-duct,  and  then  opening  the  fundus  of  the 
gall-bladder,  so  as  to  produce  a  biliary  fistula,  by  which  the  whole 
of  the  bile  was  drawn  off.  By  doing  this  operation,  and  collecting 
and  weighing  the  fluid  discharged  at  different  periods,  they  came 

to  the  conclusion  that  the  flow 
^^^'  ^^'  of  bile  begins  to  increase  within 

two  and  a  half  hours  after  the 
introduction  of  food  into  the 
stomach,  but  that  it  does  not 
reach  its  maximum  of  activity 
till  the  end  of  twelve  or  fifteen 
hours.  Other  observers,  how- 
ever, have  obtained  different 
results.  Arnold,'  for  example, 
found  the  quantity  to  be  largest 
soon  after  meals,  decreasing 
again  after  the  fourth  hour. 
Kolliker  and  Mliller,^  again, 
found  it  largest  between  the 
sixth  and  eighth  hours.  Bidder 
and  Schmidt's  experiments,  in- 
deed, strictly  speaking,  show 
only  the  time  at  which  the  bile 
is  most  actively  secreted  by  the 
liver,  but  not  when  it  is  actually 
discharged  into  the  intestine. 
Our  own  experiments,  bear- 
ing on  this  point,  were  performed  on  dogs,  by  making  a  permanent 
duodenal  fistula,  on  the  same  plan  that  gastric  fistulse  have  so  often 


Duodenal  FiSTtrLA.—n.  Stomach.  6.  Duo- 
denum, c,  c,  c.  Pancreas  ;  its  two  ducts  are  seen 
opening  into  the  duodenum,  one  near  the  orifice 
of  the  biliary  duct,  d,  the  other  a  short  distance 
lower  down.  e.  Silver  tube  passins  through  the 
abdominal  walls  and  opening  into  the  duodenum. 


»  In  Am.  Jonrn.  Med.  Sci.,  April,  1856. 


2  Ibid.,  April,  1857. 


VARIATIONS   AND    FUNCTIONS    OF    BILE.  191 

been  established  for  the  examination  of  the  gastric  juice.  (Fig.  63.) 
An  incision  was  made  through  the  abdominal  walls,  a  short  distance 
to  the  right  of  the  median  line,  the  floating  portion  of  the  duodenum 
drawn  up  toward  the  external  wound,  opened  by  a  longitudinal  in- 
cision, and  a  silver  tube,  armed  at  each  end  with  a  narrow  projecting 
collar  or  flange,  inserted  into  it  by  one  extremity,  five  and  a  half 
inches  below  the  pylorus,  and  two  and  a  half  inches  below  the 
orifice  of  the  lower  pancreatic  duct.  The  other  extremity  of  the 
tube  was  left  projecting  from  the  external  opening  in  the  abdominal 
parietes,  the  parts  secured  by  sutures,  and  the  wound  allowed  to 
heal.  After  cicatrization  was  complete,  and  the  animal  had  entirely 
recovered  his  healthy  condition  and  appetite,  the  intestinal  fluids 
were  drawn  off  at  various  intervals  after  feeding,  and  their  contents 
examined.  This  operation,  which  is  rather  more  difficult  than  that 
of  making  a  permanent  gastric  fistula,  is  nevertheless  exceedingly 
useful  when  it  succeeds,  since  it  enables  us  to  study,  not  only  the 
time  and  rate  of  the  biliary  discharge,  but  also,  as  mentioned  in  a 
previous  chapter  (Chap.  VI.),  many  other  extremely  interesting 
matters  connected  with  intestinal  digestion. 

In  order  to  ascertain  the  absolute  quantity  of  bile  discharged 
into  the  intestine,  and  its  variations  during  digestion,  the  duodenal 
fluids  were  drawn  off,  for  fifteen  minutes  at  a  time,  at  various 
periods  after  feeding,  collected,  weighed,  and  examined  separately, 
as  follows :  each  separate  quantity  was  evaporated  to  dryness,  its 
dry  residue  extracted  with  absolute  alcohol,  the  alcoholic  solution 
precipitated  with  ether,  and  the  ether-precipitate,  regarded  as  repre- 
senting the  amount  of  biliary  matters  present,  dried,  weighed,  and 
then  treated  with  Pettenkofer's  test,  in  order  to  determine,  as  nearly 
as  possible,  their  degree  of  purity  or  admixture.  The  result  of 
these  experiments  is  given  in  the  following  table.  At  the  eigh- 
teenth hour  so  small  a  quantity  of  fluid  was  obtained  that  the 
amount  of  its  biliary  ingredients  was  not  ascertained.  It  reacted 
perfectly,  however,  with  Pettenkofer's  test,  showing  that  bile  was 
really  present. 


192 


THE    BILE. 


Time  after 

Quantity  of  fluid 

Dry  residue 

Quantity  of 

Proportion  of 

feeding. 

in  16  minutes. 

of  same. 

biliary  matters. 

biliiry  matters 
to  dry  residue. 

Immediately 

640  grains 

33  grains 

10  grains 

.30 

1  hour 

1,990      " 

105      " 

4       " 

.03 

3  hours 

780      " 

60      " 

4       " 

.07 

6     " 

750      " 

73      " 

3.V     " 

.05 

9     " 

860      " 

78      " 

41     " 

.06 

12     " 

325      » 

23      " 

3|    » 

.16 

15     " 

347      " 

18      " 

4      » 

.22 

18     " 



— 

— 



21     " 

384      " 

11      " 

1       " 

.09 

24    " 

163      " 

9.',    " 

3^     " 

.34 

25     " 

151      " 

5"    " 

3       " 

.60 

From  this  it  appears  that  the  bile  passes  into  the  intestine  in  by 
far  the  largest  quantity  immediately  after  feeding,  and  within  the 
first  hour.  After  that  time  its  discharge  remains  pretty  constant ; 
not  varying  much  from  four  grains  of  solid  biliary  matters  every 
fifteen  minutes,  or  sixteen  grains  per  hour.  The  animal  used  for 
the  above  observations  weighed  thirty-six  and  a  half  pounds. 

The  next  point  to  be  ascertained  with  regard  to  this  question  is 
the  following,  viz :  What  becomes  of  the  bile  in  its  2^cissage  through 
the  intestine  f  Our  experiments,  performed  with  a  view  of  settling 
this  point,  were  tried  on  dogs.  The  animals  were  fed  with  fresh 
meat,  and  then  killed  at  various  intervals  after  the  meals,  the  abdo- 
men opened,  ligatures  placed  upon  the  intestine  at  various  points, 
and  the  contents  of  its  upper,  middle,  and  lower  portions  collected 
and  examined  separately.  The  results  thus  obtained  show  that, 
under  ordinary  circumstances,  the  bile,  which  is  quite  abundant  in 
the  duodenum  and  upper  part  of  the  small  intestine,  diminishes  in 
quantity  from  above  downward,  and  is  not  to  be  found  in  the  large 
intestine.  The  entire  quantity  of  the  intestinal  contents  also  dimi- 
nishes, and  their  consistency  increases,  as  we  approach  the  ileo- 
caecal  valve;  and  at  the  same  time  their  color  changes  from  a, light 
yellow  to  a  dark  bronze  or  blackish-green,  which  is  always  strongly 
pronounced  in  the  last  quarter  of  the  small  intestine. 

The  contents  of  the  small  and  large  intestine  were  furthermore 
evaporated  to  dryness,  extracted  with  absolute  alcohol,  and  the 
alcoholic  solutions  precipitated  with  ether ;  the  quantity  of  ether- 
precipitate  being  regarded  as  representing  approximately  that  of 
the  biliary  substances  proper.  The  result  showed  that  the  quantity 
of  this  ether-precipitate  is,  both  positively  and  relatively,  very  much 
less  in  the  large  intestine  than  in  the  small.  Its  proportion  to  the 
entire  solid  contents  is  only  one-fifth  or  one-sixth  as  great  in  the 


VARIATIONS    AND    FUNCTIONS    OF    BILE.  193 

large  intestine  as  it  is  in  the  small.  But  even  this  inconsiderable 
quantity,  found  in  contents  of  the  large  intestine,  does  not  con- 
sist of  biliary  matters ;  for  the  watery  solutions  being  treated  with 
sugar  and  sulphuric  acid,  those  from  both  the  upper  and  lower 
portions  of  the  small  intestine  always  gave  Pettenkofer's  reaction 
promptly  and  perfectly  in  less  than  a  minute  and  a  half;  while  in 
that  from  the  large  intestine  no  red  or  purple  color  was  produced, 
even  at  the  end  of  three  hours. 

The  small  intestine  consequently  contains,  at  all  times,  substances 
giving  all  the  reactions  of  the  biliary  ingredients;  while  in  the 
contents  of  the  large  intestine  no  such  substances  can  be  recognized 
by  Pettenkofer's  test. 

The  biliary  matters,  therefore,  disappear  in  their  passage  through 
the  intestine. 

In  endeavoring  to  ascertain  what  is  the  precise  function  of  the  bile 
in  the  intestine,  our  first  object  must  be  to  determine  what  part,  if 
any,  it  takes  in  the  digestive  process.  As  the  liver  is  situated,  like 
the  salivary  glands  and  the  pancreas,  in  the  immediate  vicinity  of 
the  alimentary  canal,  and  like  them,  discharges  its  secretion  into 
the  cavity  of  the  intestine,  it  seems  at  first  natural  to  regard  the 
bile  as  one  of  the  digestive  fluids.  "We  have  previously  shown, 
however,  that  the  digestion  of  all  the  different  elements  of  the  food 
is  provided  for  by  other  secretions ;  and  furthermore,  if  we  examine 
experimentally  the  digestive  power  of  bile  on  alimentary  substances, 
we  obtain  only  a  negative  result.  Bile  exerts  no  special  action  upon 
either  albuminoid,  starchy,  or  oleaginous  matters,  when  mixed  with 
them  in  test-tubes  and  kept  at  the  temperature  of  100°  F.  It  has 
therefore,  apparently,  no  direct  influence  in  the  digestion  of  these 
substances. 

It  is  a  very  remarkable  fact,  in  this  connection,  that  the  bile  pre- 
cipitates by  contact  with  the  gastric  juice.  If  four  drops  of  dog's  bile 
be  added  to  5j  of  gastric  juice  from  the  same  animal,  a  copious 
yellowish- white  precipitate  falls  down,  which  contains  the  whole  of 
the  coloring  matter  of  the  bile  which  has  been  added ;  and  if  the 
mixture  be  then  filtered,  the  filtered  fluid  passes  through  quite 
colorless.  The  gastric  juice,  however,  still  retains  its  acid  reaction. 
This  precipitation  depends  upon  the  presence  of  the  biliary  sub- 
stances proper,  viz.,  the  glyko-cholate  and  tauro-cholate  of  soda,  and 
not  upon  that  of  the  incidental  ingredients  of  the  bile.  For  if  the 
bile  be  evaporated  to  dryness  and  the  biliary  substances  extracted 
13 


194  THE    BILE. 

by  alcohol  and  precipitated  by  ether,  as  above  described,  their 
watery  solution  will  precipitate  with  gastric  juice,  in  the  same 
manner  as  fresh  bile  would  do. 

Although  the  biliary  matters,  however,  precipitate  by  contact 
with  fresh  gastric  juice,  they  do  not  do  so  ivith  gastric  juice  which  holds 
albuminose  in  solution.  We  have  invariably  found  that  if  the  gas- 
tric juice  be  digested  for  several  hours  at  the  temperature  of  100° 
F.,  with  boiled  white  of  egg,  the  filtered  fluid,  which  contains  an 
abundance  of  albuminose,  will  no  longer  give  the  slightest  precipi- 
tate on  the  addition  of  bile,  or  of  a  watery  solution  of  the  biliary 
substances,  even  in  very  large  amount.  The  gastric  juice  and  the 
bile,  therefore,  are  not  finally  antagonistic  to  each  other  in  the 
digestive  process,  though  at  first  they  produce  a  precipitate  on 
being  mingled  together. 

It  appears,  however,  from  the  experiments  detailed  above,  that 
the  secretion  of  the  bile  and  its  discharge  into  the  intestine  are  not 
confined  to  the  periods  of  digestion,  but  take  place  constantly,  and 
continue  even  after  the  animal  has  been  kept  for  many  days  with- 
out food.  These  facts  would  lead  us  to  regard  the  bile  as  simply 
an  excrementitious  fluid ;  containing  only  ingredients  resulting  from 
the  waste  and  disintegration  of  the  animal  tissues,  and  not  intended 
to  perform  any  particular  function,  digestive  or  otherwise,  but 
merely  to  be  eliminated  from  the  blood,  and  discharged  from  the 
system.  The  same  view  is  more  or  less  supported,  also,  by  the 
following  facts,  viz  : — 

1st.  The  bile  is  produced,  unlike  all  the  other  animal  secretions, 
from  venous  blood ;  that  is,  the  blood  of  the  portal  vein,  which  has 
already  become  contaminated  by  circulation  through  the  abdominal 
organs,  and  may  be  supposed  to  contain  disorganized  and  efi'ete  in- 
gredients; and 

2d.  Its  complete  suppression  produces,  in  the  human  subject, 
symptoms  of  poisoning  of  the  nervous  system,  analogous  to  those 
which  follow  the  suppression  of  the  urine,  or  the  stoppage  of  respi- 
ration, and  the  patient  dies,  usually  in  a  comatose  condition,  at  the 
end  of  ten  or  twelve  days. 

The  above  circumstances,  taken  together,  would  combine  to 
make  it  appear  that  the  bile  is  simply  an  excrementitious  fluid,  not 
necessary  or  useful  as  a  secretion,  but  only  destined,  like  the  urine, 
to  be  eliminated  and  discharged.  Nevertheless,  experiment  has 
shown  that  such  is  not  the  case ;  and  that,  in  point  of  fact,  it  is 
necessary  for  the  life  of  the  animal,  not  only  that  the  bile  be  secreted 


VARIATIONS    AXD    FUNCTIONS    OF    BILE.  195 

and  discharged,  but  furthermore  that  it  be  discharged  into  the 
intestine,  and  pass  through  the  tract  of  the  alimentary  canal.  The 
most  satisfactory  experiments  of  this  kind  are  those  of  Bidder  and 
Schmidt,'  in  which  they  tied  the  common  biliary  duct  in  dogs,  and 
theu  established  a  permanent  fistula  in  the  fundus  of  the  gall-bladder, 
through  which  the  bile  was  allowed  to  flow  by  a  free  external  orifice. 
In  this  manner  the  bile  was  effectually  excluded  from  the  intestine, 
but  at  the  same  time  was  freely  and  wholly  discharged  from  the 
body,  by  the  artificial  fistula.  If  the  bile  therefore  were  simply  an 
excrementitious  fluid,  its  deleterious  ingredients  being  all  eliminated 
as  usual,  the  animals  would  not  suffer  any  serious  injury  from  this 
operation.  If,  on  the  contrary,  they  were  found  to  suffer  or  die  in 
consequence  of  it,  it  would  show  that  the  bile  has  really  some 
important  function  to  perform  in  the  intestinal  canal,  and  is  not 
simply  excrementitious  in  its  nature. 

The  result  showed  that  the  effects  of  such  an  experiment  were 
fatal  to  the  animal.  Four  dogs  only  survived  the  immediate  effects 
of  the  operation,  and  were  afterward  frequently  used  for  purposes 
of  experiment.  One  of  them  was  an  animal  from  which  the  spleen 
had  been  previously  removed,  and  whose  appetite,  as  usual  after 
this  operation,  was  morbidly  ravenous;  his  system,  accordingly, 
being  placed  under  such  unnatural  conditions  as  to  make  him  an 
unfit  subject  for  further  experiment.  In  the  second  animal  that 
survived,  the  communication  of  the  biliary  duct  with  the  intestine 
became  re-established  after  eighteen  days,  and  the  experiment  con- 
sequently had  no  result.  In  the  remaining  two  animals,  however, 
everything  was  successful.  The  fistula  in  the  gall-bladder  became 
permanently  established ;  and  the  bile-duct,  as  was  proved  subse- 
quently by  post-mortem  examination,  remained  cornpletely  closed, 
so  that  no  bile  found  its  way  into  the  intestine.  Both  these  ani- 
mals died ;  one  of  them  at  the  end  of  twenty-seven  days,  the  other 
at  the  end  of  thirty-six  days.  In  both,  the  symptoms  were  nearly 
the  same,  viz.,  constant  and  progressive  emaciation,  which  proceeded 
to  such  a  degree  that  nearly  every  trace  of  fat  disappeared  from  the 
body.  The  loss  of  flesh  amounted,  in  one  case,  to  more  than  two- 
fifths,  and  in  the  other  to  nearly  one-half  the  entire  weight  of  the 
animal.  There  was  also  a  falling  off"  of  the  hair,  and  an  unusually 
disagreeable,  putrescent  odor  in  the  feces  and  in  the  breath.  Not- 
withstanding this,  the  appetite  remained  good.     Digestion  was  not 

>  Op.  cit.,  p.  103, 


196  THE    BILE. 

essentially  interfered  with,  and  none  of  the  food  was  discharged 
with  the  feces ;  but  there  was  much  rumbling  and  gurgling  in  the 
intestines,  and  abundant  discharge  of  flatus,  more  strongly  marked 
in  one  instance  than  in  the  other.  There  was  no  pain ;  and  death 
took  place,  at  last,  without  any  violent  symptoms,  but  by  a  simple 
and  gradual  failure  of  the  vital  powers, 

A  similar  experiment  has  been  successfully  performed  by  Prof. 
A.  Flint,  Jr.^  In  this  instance  the  animal  lived  for  thirty- eight 
days  after  the  operation,  and  died  finally  of  inanition ;  the  symp- 
toms agreeing  in  every  important  particular,  with  those  reported 
by  Bidder  and  Schmidt. 

How  Is  it,  then,  that  although  the  bile  be  not  an  active  agent  in 
digestion,  its  presence  in  the  alimentary  canal  is  still  essential  to 
life  ?  "What  of&ce  does  it  perform  there,  and  how  is  it  finally  dis- 
posed of? 

We  have  already  shown  that  the  bile  disappears  in  its  passage 
through  the  intestine.  This  disappearance  may  be  explained  in 
two  different  ways.  First,  the  biliary  matters  may  be  actually  re- 
absorbed from  the  intestine,  and  taken  up  by  the  bloodvessels ;  or 
secondly,  they  may  be  so  altered  and  decomposed  by  the  intestinal 
flaids  as  to  lose  the  power  of  giving  Pettenkofer's  reaction  with 
sugar  and  sulphuric  acid,  and  so  pass  off  with  the  feces  in  an 
insoluble  form.  Bidder  and  Schmidt^  have  finally  determined  this 
point  in  a  satisfactory  manner;  and  have  demonstrated  that  the 
biliary  substances  are  actually  reabsorbed,  by  showing  that  the 
quantity  of  sulphur  present  in  the  feces  is  far  inferior  to  that 
contained  in  the  biliary  ingredients  as  they  are  discharged  into  the 
intestine. 

These  observers  collected  and  analyzed  all  the  feces  passed,  dur- 
ing five  days,  by  a  healthy  dog,  weighing  17.7  pounds.  The  entire 
fecal  mass  during  this  period  weighed  1508.15  grains, 

„     ,  .  .       f  Water 874.20  grains. 

Containing  <  ° 

^  I  Solid  residue 633.95        " 


1508.15 


'  American  Journ.  Med.  Sci.,  October,  1862. 
2  Op.  cit.,  p.  217. 


VARIATIONS    AND    FUNCTIONS    OF    BILE.  197 

The  solid  residue  was  composed  as  follows : — 

Neutral  fat,  soluble  in  ether     .         .     43.710  grains. 

Fat,  with  traces  of  biliary  matter     .     77.035         " 

Alcohol  extract  with  biliary  matter    58.900  containing  1.085  grs.  of  sulphur. 

Substances  not  of  a  biliary  nature 

extracted   by  muriatic  acid  and 

hot  alcohol  ....  148.800  containing  1.302  grs.  of  sulphur. 

2.387 
Fatty  acids  with  oxide  of  iron        .     98.425 

Residue  consisting  of  hair,  sand,  &c.,  207.080 


633.950 

Now,  as  it  has  already  been  shown  that  the  dog  secretes,  during 
24  hours,  6.916  grains  of  solid  biliary  matter  for  every  pound  weight 
of  the  whole  body,  the  entire  quantity  of  biliary  matter  secreted 
in  five  days  by  the  above  animal,  weighing  17.7  pounds,  must  have 
been  612.5  grains,  or  nearly  as  much  as  the  whole  weight  of  the 
dried  feces.  But  furthermore,  the  natural  proportion  of  sulphur 
in  dog's  bile  (derived  from  the  uncrystallizable  biliary  matter),  is  six 
per  cent,  of  the  dry  residue.  The  612.5  grains  of  dry  bile,  secreted 
during  five  days,  contained,  therefore,  36.75  grains  of  sulphur. 
But  the  entire  quantity  of  sulphur,  existing  in  any  form  in  the 
feces,  was  5.952  grains;  and  of  this  only  2.387  grains  were  derived 
from  substances  which  could  have  been  the  products  of  biliary 
matters — the  remainder  being  derived  from  the  hairs  which  are 
always  contained  in  abundance  in  the  feces  of  the  dog.  That  is, 
not  more  than  one-fifteenth  part  of  the  sulphur,  originally  present 
in  the  bile,  could  be  detected  in  the  feces.  As  this  is  a  simple 
chemical  element,  not  decomposable  by  any  known  means,  it  must, 
accordingly,  have  been  reabsorbed  from  the  intestine. 

We  have  endeavored  to  complete  the  evidence  thus  furnished  by 
Bidder  and  Schmidt,  and  to  demonstrate  directly  the  reabsorption 
of  the  biliary  matters,  by  searching  for  them  in  the  ingredients  of 
the  portal  blood.  We  have  examined,  for  this  purpose,  the  portal 
blood  of  dogs,  killed  at  various  periods  after  feeding.  The  animals 
were  killed  by  section  of  the  medulla  oblongata,  a  ligature  imme- 
diately placed  on  the  portal  vein,  while  the  circulation  was  still 
active,  and  the  requisite  quantity  of  blood  collected  by  opening 
the  vein.  The  blood  was  sometimes  immediately  evaporated  to 
dryness  by  the  water  bath.  Sometimes  it  was  coagulated  by  boil- 
ing in  a  porcelain  capsule,  over  a  spirit  lamp,  with  water  and  an 
excess  of  sulphate  of  soda,  and  the  filtered  watery  solution  after- 
ward examined.     But  most  frequently  the  blood,  after  being  col- 


198  THE    BILE. 

lected  from  the  vein,  was  coagulated  bj  the  gradual  addition  of 
three  times  its  volume  of  alcohol  at  ninetj-five  per  cent,,  stirring 
the  mixture  constantly,  so  as  to  make  the  coagulation  gradual  and 
uniform.  It  was  then  filtered,  the  moist  mass  remaining  on  the  filter 
subjected  to  strong  pressure  in  a  linen  bag,  by  a  porcelain  press, 
and  the  fluid  thus  obtained  added  to  that  previously  filtered.  The 
entire  spirituous  solution  was  then  evaporated  to  dryness,  the  dry 
residue  extracted  with  absolute  alcohol,  and  the  alcoholic  solution 
treated  as  usual,  with  ether,  &c.,  to  discover  the  presence  of  biliary 
matters.  In  every  instance  blood  was  taken  at  the  same  time  from 
the  jugular  vein,  or  the  abdominal  vena  cava,  and  treated  in  the 
same  way  for  purposes  of  comparison. 

We  have  examined  the  blood,  in  this  way,  one,  four,  six,  nine, 
eleven  and  a  half,  twelve,  and  twenty  hours  after  feeding.  As  the 
result  of  these  examinations,  we  have  found  that  in  the  venous 
blood,  both  of  the  portal  vein  and  of  the  general  circulation,  there 
exists  a  substance  soluble  in  water  and  absolute  alcohol,  and  pre- 
cipitable  by  ether  from  its  alcoholic  solution.  This  substance  is 
often  considerably  more  abundant  in  the  portal  blood  than  in  that 
taken  from  the  general  venous  system.  It  adheres  closely  to  the 
sides  of  the  glass  after  precipitation,  so  that  it  is  always  difficult, 
and  often  impossible,  to  obtain  enough  of  it,  mixed  with  ether,  for 
microscopic  examination.  It  dissolves,  also,  like  the  biliary  sub- 
stances, with  great  readiness  in  water ;  but  in  no  instance  have  we 
ever  been  able  to  obtain  from  it  such  a  satisfactory  reaction  with 
Pettenkofer's  test,  as  would  indicate  the  presence  of  bile.  This  is 
not  because  the  reaction  is  masked,  as  might  be  suspected,  by  some 
of  the  other  ingredients  of  the  blood;  for  if  at  the  same  time,  two 
drops  of  bile  be  added  to  half  an  ounce  of  blood  taken  from  the 
abdominal  vena  cava,  and  the  two  specimens  treated  alike,  the  ether- 
precipitate  may  be  considered  more  abundant  in  the  case  of  the 
portal  blood ;  and  yet  that  from  the  blood  of  the  vena  cava,  dis- 
solved in  water,  will  give  Pettenkofer's  reaction  for  bile  perfectly, 
while  that  of  the  portal  blood  will  give  no  such  reaction. 

Notwithstanding,  then,  the  irresistible  evidence  afforded  by  the 
experiments  of  Bidder  and  Schmidt,  that  the  biliary  matters  are 
really  taken  up  by  the  portal  blood,  we  have  failed  to  recognize 
them  there  by  Pettenkofer's  test.  They  must  accordingly  undergo 
certain  alterations  in  the  intestine,  previously  to  their  absorption, 
so  that  they  no  longer  give  the  ordinary  reaction  of  the  biliary  sub- 
stances.   We  cannot  say,  at  present,  precisely  what  these  alterations 


VARIATIONS    AND    FL^NCTIONS    OF    BILE.  199 

are ;  but  tliey  are  evidently  transformations  of  a  catalytic  nature, 
produced  by  the  contact  of  the  bile  with  the  intestinal  juices. 

The  bile,  therefore,  is  a  secretion  which  has  not  yet  accomplished 
its  function  when  it  is  discharged  from  the  liver  and  poured  into  the 
intestine.  On  the  contrary,  during  its  passage  through  the  intestine 
it  is  still  in  the  interior  of  the  body,  in  contact  with  glandular  sur- 
faces, and  mingled  with  various  organic  substances,  the  ingredients 
of  the  intestinal  fluids,  which  act  upon  it  as  catalytic  bodies,  and 
produce  in  it  new  transformations.  This  may  account  for  the  fact 
stated  above,  that  the  bile,  though  a  constant  and  uninterrupted 
secretion,  is  nevertheless  poured  into  the  intestine  in  the  greatest 
abundance  immediately  after  a  hearty  meal.  This  is  not  because  it 
is  to  take  any  direct  part  in  the  digestion  of  the  food ;  but  because 
the  intestinal  fluids,  being  themselves  present  at  that  time  in  the 
greatest  abundance,  can  then  act  upon  and  decompose  the  greatest 
quantity  of  bile.  At  all  events,  the  biliary  ingredients,  after  being 
altered  and  transformed  in  the  intestine,  as  they  might  be  in  the 
interior  of  a  glandular  organ,  re-enter  the  blood  under  some  new 
form,  and  are  carried  away  by  the  circulation,  to  complete  their 
function  in  some  other  part  of  the  body. 


200  FORMATION    OF    SUGAR   IN    THE   LIVER. 


CHAPTER    IX. 

FOEMATION   OF  SUGAR  IN  THE  LITER. 

Beside  the  secretion  of  bile,  the  liver  performs  also  another 
exceedingly  important  function,  viz.,  the  production  of  sugar  by  a 
metamorphosis  of  some  of  its  organic  ingredients. 

Under  ordinary  circumstances  a  considerable  quantity  of  sac- 
charine matter  is  introduced  with  the  food,  or  produced  from 
starchy  substances,  by  the  digestive  process,  in  the  intestinal  canal. 
In  man  and  the  herbivorous  animals,  accordingly,  an  abundant 
supply  of  sugar  is  derived  from  these  sources;  and,  as  we  have 
already  shown,  the  sugar  thus  introduced  is  necessary  for  the  proper 
support  of  the  vital  functions.  For  though  the  saccharine  matter 
absorbed  from  the  intestine  is  destroyed  by  decomposition  soon 
after  entering  the  circulation,  yet  the  chemical  changes  by  which 
its  decomposition  is  effected  are  themselves  necessary  for  the  proper 
constitution  of  the  blood,  and  the  healthy  nutrition  of  the  tissues. 
Experiment  shows,  however,  that  the  system  does  not  depend,  for 
its  supply  of  sugar,  entirely  upon  external  sources ;  but  that  sac- 
charine matter  is  also  produced  independently,  in  the  tissue  of  the 
liver,  whatever  may  be  the  nature  of  the  food  upon  which  the 
animal  subsists. 

This  important  function  was  first  discovered  by  M.  Claude  Ber- 
nard^ in  1848,  and  described  by  him  under  the  name  of  the  glyco- 
genic function  of  the  liver. 

It  has  long  been  known  that  sugar  may  be  abundantly  secreted, 
under  some  circumstances,  when  no  vegetable  matters  have  been 
taken  with  the  food.  The  milk,  for  example,  of  all  animals,  car- 
nivorous as  well  as  herbivorous,  contains  a  notable  proportion  of 
sugar ;  and  the  quantity  thus  secreted,  during  lactation,  is  in  some 
instances  very  great.  In  the  human  subject,  also,  when  suffering 
from  diabetes,  the  amount  of  saccharine  matter  discharged  with  the 

'  Nouvelle  Fonction  du  Foie.     Paris,  1853. 


FORMATION    OF    SUGAR    IN    THE    LIVER.  201 

urine  lias  often  appeared  to  be  altogether  out  of  proportion  to  that 
■which,  could  be  accounted  for  by  the  vegetable  substances  taken  as 
food.  The  experiments  of  Bernard,  the  most  important  of  which 
we  have  repeatedly  confirmed,  in  common  with  other  investigators, 
show  that  in  these  instances  most  of  the  sugar  has  an  internal 
origin,  and  that  it  first  makes  its  appearance  in  the  tissue  of  the 
liver. 

If  a  carnivorous  animal,  as,  for  example,  a  dog  or  a  cat,  be  fed 
for  several  days  exclusively  upon  meat,  and  then  killed,  the  liver 
alone  of  all  the  internal  organs  is  found  to  contain  sugar  among  its 
other  ingredients.  For  this  purpose,  a  portion  of  the  organ  should 
be  cut  into  small  pieces,  reduced  to  a  pulp  by  grinding  in  a  mortar 
with  a  little  water,  and  the  mixture  coagulated  by  boiling  with  an 
excess  of  sulphate  of  soda,  in  order  to  precipitate  the  albuminous 
and  coloring  matters.  The  filtered  fluid  will  then  reduce  the  oxide 
of  copper,  with  great  readiness,  on  the  application  of  Trommer's 
test.  A  decoction  of  the  same  tissue,  mixed  with  a  little  yeast,  will 
also  give  rise  to  fermentation,  producing  alcohol  and  carbonic  acid, 
as  is  usual  with  saccharine  solutions.  On  the  contrary,  the  tissues 
of  the  spleen,  the  kidneys,  the  lungs,  the  muscles,  &c.,  treated  in 
the  same  way,  give  no  indication  of  sugar,  and  do  not  reduce  the 
salts  of  copper.  Every  other  organ  in  the  body  may  be  entirely 
destitute  of  sugar,  but  the  liver  always  contains  it  in  considerable 
quantity,  provided  the  animal  be  healthy.  Even  the  blood  of  the 
portal  vein,  examined  by  a  similar  process,  contains  no  saccharine 
element,  and  yet  the  tissue  of  the  organ  supplied  by  it  shows  an 
abundance  of  saccharine  ingredients. 

It  is  remarkable  for  how  long  a  time  the  liver  will  continue  to 
exhibit  the  presence  of  sugar,  after  all  external  supplies  of  this 
substance  have  been  cut  off.  Bernard  kept  two  dogs  under  his  own 
observation,  one  for  a  period  of  three,  the  other  of  eight  months,^ 
during  which  period  they  were  confined  strictly  to  a  diet  of  animal 
food  (boiled  calves'  heads  and  tripe),  and  then  killed.  Upon  exa- 
mination, the  liver  was  found,  in  each  instance,  to  contain  a  propor- 
tion of  sugar  fully  equal  to  that  present  in  the  organ  under  ordinary 
circumstances. 

The  sugar,  therefore,  which  is  found  in  the  liver  after  death,  is  a 
normal  ingredient  of  the  hepatic  tissue.  It  is  not  formed  in  other 
parts  of  the  body,  nor  absorbed  from  the  intestinal  canal,  but  takes 

'  Nouvelle  Fonction  du  Foie,  p.  50. 


202 


FORMATION    OF    SUGAR    IN    THE    LIVER. 


its  origin  in  tlie  liver  itself ;  it  is  produced,  as  a  new  formation,  by 
a  secreting  process  in  the  tissue  of  the  organ. 

The  presence  of  sugar  in  the  liver  is  common  to  all  species  of 
animals,  so  far  as  is  yet  known.  Bernard  found  it  invariably  in 
monkeys,  dogs,  cats,  rabbits,  the  horse,  the  ox,  the  goat,  the  sheep, 
in  birds,  in  reptiles,  and  in  most  kinds  of  fish.  It  was  only  in  two 
species  of  fish,  viz.,  the  eel  and  the  ray  (Mursena  anguilla  and  Eaia 
batis),  that  he  sometimes  failed  to  discover  it ;  but  the  failure  in 
these  instances  was  apparently  owing  to  the  commencing  putres- 
cence of  the  tissue,  by  which  the  sugar  had  probably  been  destroyed. 
In  the  fresh  liver  of  the  human  subject,  examined  after  death  from 
accidental  violence,  sugar  was  found  to  be  present  in  the  proportion 
of  1.10  to  2.14  per  cent,  of  the  entire  weight  of  the  organ. 

The  following  list  shows  the  average  percentage  of  sugar  present 
in  the  healthy  liver  of  man  and  different  species  of  animals,  accord- 
ing to  the  examinations  of  Bernard : — 


In  man   . 
"  monkey 
"  dog     . 
"  cat 
"  rabbit 
"  sbeep 


Percentage  of  Sugar  in  the  Liver. 

.  1.68  In  ox 

.  2.15  "  horse 

.  1.69  "  goat    . 

.  1.94  "  birds 

.  1.94  "  reptiles 

.  2.00  "  fish 


2.30 


With  regard  to  the  nature  and  properties  of  the  liver  sugar,  it 
resembles  very  closely  glucose,  or  the  sugar  of  starch,  the  sugar  of 
honey,  and  the  sugar  of  milk,  though  it  is  not  absolutely  identical 
with  either  one  of  them.  Its  solution  reduces,  as  we  have  seen,  the 
salts  of  copper  in  Trommer's  test,  and  becomes  colored  brown  when 
boiled  with  caustic  potassa.  It  ferments  very  readily,  also,  when 
mixed  with  yeast  and  kept  at  the  temperature  of  70"  to  100°  F. 
It  is  distinguished  from  all  the  other  sugars,  according  to  Bernard,^ 
by  the  readiness  with  which  it  becomes  decomposed  in  the  blood — 
since  cane  sugar  and  beet  root  sugar,  if  injected  into  the  circulation 
of  a  living  animal,  pass  through  the  system  without  sensible  decom- 
position, and  are  discharged  unchanged  with  the  urine ;  sugar  of 
milk  and  glucose,  if  injected  in  moderate  quantity,  are  decomposed 
in  the  blood,  but  if  introduced  in  greater  abundance  make  their 
appearance  also  in  the  urine ;  while  a  solution  of  liver  sugar,  though 
injected  in  much  larger  quantity  than  either  of  the  others,  may  dis- 


>  Lemons  de  Physiologie  Experimentale.     Paris,  1855,  p.  213. 


FORMATION    OF    SUGAR    IN    THE    LIVER.  203 

appear  altogether  in  the  circulation,  without  passing  off  by  the 
kidneys. 

This  substance  is  therefore  a  sugar  of  animal  origin,  similar  in 
its  properties  to  other  varieties  of  saccharine  matter,  derived  from 
different  sources. 

The  sugar  of  the  liver  is  not  produced  in  the  blood  by  a  direct 
decomposition  of  the  elements  of  the  circulating  fluid  in  the  vessels 
of  the  organ,  but  takes  its  origin  in  the  solid  substance  of  the  hepatic 
tissue,  as  a  natural  ingredient  of  its  organic  texture.  The  blood 
which  may  be  pressed  out  from  a  liver  recently  extracted  from  the 
body,  it  is  true,  contains  sugar  ;  but  this  sugar  it  has  absorbed  from 
the  tissue  of  the  organ  in  which  it  circulates.  This  is  demonstrated 
by  the  singular  fact  that  the  fresh  liver  of  a  recently  killed  animal, 
though  it  may  be  entirely  drained  of  blood  and  of  the  sugar  which 
it  contained  at  the  moment  of  death,  will  still  continue  for  a  certain 
time  to  produce  a  saccharine  substance.  If  such  a  liver  be  injected 
with  water  by  the  portal  vein,  and  all  the  blood  contained  in  its 
vessels  washed  out  by  the  stream,  the  water  which  escapes  by  the 
hepatic  vein  will  still  be  found  to  contain  sugar.  M.  Bernard  has 
found^  that  if  all  the  sugar  contained  in  a  fresh  liver  be  extracted  in 
this  manner  by  a  prolonged  watery  injection,  so  that  neither  the 
water  which  escapes  by  the  hepatic  vein,  nor  the  substance  of  the 
liver  itself,  contain  any  further  traces  of  sugar,  and  if  the  organ  be 
then  laid  aside  for  twenty-four  hours,  both  the  tissue  of  the  liver  and 
the  fluid  which  exudes  from  it  will  be  found  at  the  end  of  that  time 
to  have  again  become  highly  saccharine.  The  sugar,  therefore,  is 
evidently  not  produced  in  the  blood  circulating  through  the  liver, 
but  in  the  substance  of  the  organ  itself.  Once  having  originated 
in  the  hepatic  tissue,  it  is  absorbed  thence  by  the  blood,  and  trans- 
ported by  the  circulation,  as  we  shall  hereafter  show,  to  other  parts 
of  the  body. 

The  sugar  which  thus  originates  in  the  tissue  of  the  liver,  is  pro- 
duced by  a  mutual  decomposition  and  transformation  of  various 
other  ingredients  of  the  hepatic  substance ;  these  chemical  changes 
being  a  part  of  the  nutritive  process  by  which  the  tissue  of  the 
organ  is  constantly  sustained  and  nourished.  There  is  probably  a 
series  of  several  different  transformations  which  take  place  in  this 
manner,  the  details  of  which  are  not  yet  known  to  us.  It  has  been 
discovered,  however,  that  one  change  at  least  precedes  the  final 

'  Gazette  Hebdomadaire,  Paris,  Oct.  5,  1855. 


204  FORMATION    OF    SUGAR    IX    THE    LIVER. 

production  of  saccharine  matter ;  and  that  the  sugar  itself  is  pro- 
duced bj  the  transformation  of  another  peculiar  substance,  of  ante- 
rior formation.  This  substance,  which  precedes  the  formation  of 
sugar,  and  which  is  itself  produced  in  the  tissue  of  the  liver,  is 
known  by  the  name  of  glycogenic  matter,  or  glycogene. 

This  glycogenic  matter  may  be  extracted  from  the  liver  in  the 
following  manner.  The  organ  is  taken  immediately  from  the  body 
of  the  recently  killed  animal,  cut  into  small  pieces,  and  coagulated  by 
being  placed  for  a  few  minutes  in  boiling  water.  This  is  in  order 
to  prevent  the  albuminous  liquids  of  the  organ  from  acting  upon 
the  glycogenic  matter  and  decomposing  it  at  a  medium  temperature. 
The  coagulated  tissue  is  then  drained,  placed  in  a  mortar,  reduced 
to  a  pulp  by  bruising  and  grinding,  and  afterward  boiled  in  dis- 
tilled water  for  a  quarter  of  an  hour,  by  which  the  glycogenic 
matter  is  extracted  and  held  in  solution  by  the  boiling  water. 

The  liquid  of  decoction,  which  should  be  as  concentrated  as  pos- 
sible, must  then  be  expressed,  strained,  and  filtered,  after  which  it 
appears  as  a  strongly  opalescent  fluid,  of  a  slightly  yellowish  tinge. 
The  glycogenic  matter  which  is  held  in  solution  may  be  precipi- 
tated by  the  addition  to  the  filtered  fluid  of  five  times  its  volume 
of  alcohol.  The  precipitate,  after  being  repeatedly  washed  with 
alcohol  in  order  to  remove  sugar  and  biliary  matters,  may  then  be 
redissolved  in  distilled  water.  It  may  be  precipitated  from  its 
watery  solution  either  by  alcohol  in  excess  or  by  crystallizable 
acetic  acid,  in  both  of  which  it  is  entirely  insoluble,  and  may  be 
afterward  kept  in  the  dry  state  for  an  indefinite  time  without  losing 
its  properties. 

The  glycogenic  matter,  obtained  in  this  way,  is  regarded  as 
intermediate  in  its  nature  and  properties  between  hydrated  starch 
and  dextrine.  Its  ultimate  composition,  according  to  M.  Pelouze,' 
is  as  follows : — 

^12^12^12* 

When  brought  into  contact  with  iodine,  it  produces  a  coloration 
varying  from  violet  to  a  deep,  clear,  maroon  red.  It  does  not 
reduce  the  salts  of  copper  in  Trommer's  test,  nor  does  it  ferment 
when  placed  in  contact  with  yeast  at  the  proper  temperature.  It 
does  not,  therefore,  of  itself  contain  sugar.  It  may  easily  be  con- 
verted into  sugar,  however,  by  contact  with  any  of  the  animal 
ferments,  as,  for  example,  those  contained  in  the  saliva,  or  in  the 

'  Journal  de  Physiologie,  Paris,  1858,  p.  552. 


FORMATION    OF    SUGAR    IN    THE    LIVER.  205 

blood.  If  a  solution  of  glycogenic  matter  be  mixed  with  fresb. 
human  saliva,  and  kept  for  a  few  minutes  at  the  temperature  of 
100°  ¥.,  the  mixture  will  then  be  found  to  have  acquired  the  power 
of  reducing  the  salts  of  copper  and  of  entering  into  fermentation  by 
contact  with  yeast.  The  glycogenic  matter  has  therefore  been 
converted  into  sugar  by  a  process  of  catalysis,  in  the  same  manner 
as  vegetable  starch  would  be  transformed  under  similar  conditions. 

The  glycogenic  matter  which  is  thus  destined  to  be  converted 
into  sugar,  is  formed  in  the  liver  by  the  processes  of  nutrition.  It 
may  be  extracted,  as  we  have  seen  above,  from  the  hepatic  tissue 
of  carnivorous  animals,  and  is  equally  present  when  they  have  been 
exclusively  confined  for  many  days  to  a  meat  diet.  It  is  not  in- 
troduced with  the  food  ;  for  the  fleshy  meat  of  the  herbivora  does 
not  contain  it  in  appreciable  quantity,  though  these  animals  so 
constantly  take  starchy  substances  with  their  food.  In  them,  the 
starchy  matters  are  transformed  into  sugar  by  digestion,  and  the 
sugar  so  produced  is  rapidly  destroyed  after  entering  the  circula- 
tion ;  so  that  usually  neither  saccharine  nor  starchy  substances  are 
to  be  discovered  in  the  muscular  tissue.  M.  Poggiale'  found  that  in 
very  many  experiments,  performed  by  a  commission  of  the  French 
Academy  for  the  purpose  of  examining  this  subject,  glycogenic 
matter  was  detected  in  ordinary  butcher's  meat  only  once.  We 
have  also  found  it  to  be  absent  from  the  fresh  meat  of  the  bullock's 
heart,  when  examined  in  the  manner  described  above.  Neverthe- 
less, in  dogs  fed  exclusively  upon  this  food  for  eight  days,  glycogenic 
matter  may  be  found  in  abundance  in  the  liver,  while  it  does  not 
exist  in  other  parts  of  the  body,  as  the  spleen,  kidney,  lungs,  &c. 

Furthermore,  in  a  dog  fed  exclusively  for  eight  days  upon  the 
fresh  meat  of  the  bullock's  heart,  and  then  killed  four  hours  after 
a  meal  of  the  same  food,  at  which  time  intestinal  absorption  is 
going  on  in  full  vigor,  the  liver  contains,  as  above  mentioned,  both 
glycogenic  matter  and  sugar ;  but  neither  sugar  nor  glycogenic  mat- 
ter can  be  found  in  the  blood  of  the  portal  vein,  when  subjected  to 
a  similar  examination. 

The  glycogenic  matter,  accordingly,  does  not  originate  from  any 
external  source,  but  is  formed  in  the  tissue  of  the  liver ;  where  it 
is  soon  afterward  transformed  into  sugar,  while  still  forming  a  part 
of  the  substance  of  the  organ. 

The  formation  of  sugar  in  the  liver  is  therefore  a  function  com- 

'  Journal  dn  Physiologie,  Paris,  1858,  p.  558. 


206  FORMATION    OF    SUGAR   IN"   THE    LIVER. 

posed  of  two  distinct  and  successive  processes,  viz :  first,  the  forma- 
tion, in  the  hepatic  tissue,  of  a  glycogenic  matter,  having  some 
resemblance  to  dextrine;  and  secondly,  the  conversion  of  this 
glycogenic  matter  into  sugar,  by  a  process  of  catalysis  and  trans- 
formation. 

The  sugar  thus  produced  in  the  substance  of  the  liver  is  absorbed 
from  it  by  the  blood  circulating  in  its  vessels.  The  mechanism  of 
this  absorption  is  probably  the  same  with  that  which  goes  on  in 
other  parts  of  the  circulation.  '  It  is  a  process  of  transudation  and 
endosmosis,  by  which  the  blood  in  the  vessels  takes  up  the  saccha- 
rine fluids  of  the  liver,  during  its  passage  through  the  organ. 
While  the  blood  of  the  portal  vein,  therefore,  in  an  animal  fed 
exclusively  upon  meat,  contains  no  sugar,  the  blood  of  the  hepatic 
vein,  as  it  passes  upward  to  the  heart,  is  always  rich  in  saccharine 
ingredients.  This  difference  can  be  easily  demonstrated  by  exa- 
mining comparatively  the  two  kinds  of  blood,  portal  and  hepatic, 
from  the  recently  killed  animal.  The  blood  in  its  passage  through 
the  liver  is  found  to  have  acquired  a  new  ingredient,  and  shows, 
upon  examination,  all  the  properties  of  a  saccharine  liquid. 

The  sugar  produced  in  the  liver  is  accordingly  to  be  regarded  as 
a  true  secretion,  formed  by  the  glandular  tissue  of  the  organ,  by  a 
similar  process  to  that  of  other  glandular  secretions.  It  differs 
from  the  latter,  not  in  the  manner  of  its  production,  but  only  in 
the  mode  of  its  discharge.  For  while  the  biliary  matters  produced 
in  the  liver  are  absorbed  by  the  hepatic  ducts  and  conducted  down- 
ward to  the  gall-bladder  and  the  intestine,  the  sugar  is  absorbed  by 
the  bloodvessels  of  the  organ  and  carried  upward,  by  the  hepatic 
veins,  toward  the  heart  and  the  general  circulation. 

The  production  of  sugar  in  the  liver  during  health  is  a  constant 
process,  continuing,  in  many  cases,  for  several  days  after  the  animal 
has  been  altogether  deprived  of  food.  Its  activity,  however,  like 
that  of  most  other  secretions,  is  subject  to  periodical  augmentation 
and  diminution.  Under  ordinary  circumstances,  the  sugar,  which 
is  absorbed  by  the  blood  from  the  tissue  of  the  liver,  disappears 
very  soon  after  entering  the  circulation.  As  the  bile  is  transformed 
in  the  intestine,  so  the  sugar  is  decomposed  in  the  blood.  "We  are 
not  yet  acquainted,  however,  with  the  precise  nature  of  the  changes 
which  it  undergoes  after  entering  the  vascular  system.  It  is  very 
probable,  according  to  the  views  of  Lehmann  and  Eobin,  that  it  is 
at  first  converted  into  lactic  acid  (CgHgOg),  which  decomposes  in 
turn  the  alkaline  carbonates,  setting  free  carbonic  acid,  and  forming 


FORMATION    OF    SUGAR    IN    THE    LIVER.  207 

lactates  of  soda  and  potassa.  Bat  whatever  be  the  exact  mode  of 
its  transformation,  it  is  certain  that  the  sugar  disappears  rapidly ; 
and  while  it  exists  in  considerable  quantity  in  the  liver  and  in  the 
blood  of  the  hepatic  veins  and  the  right  side  of  the  heart,  it  is  not 
usually  to  be  found  in  the  pulmonary  veins  nor  in  the  blood  of  the 
general  circulation. 

About  two  and  a  half  or  three  hours,  however,  after  the  ingestion 
of  food,  according  to  the  investigations  of  Bernard,  the  circulation 
of  blood  through  the  portal  system  and  the  liver  becomes  consider- 
ably accelerated.  A  larger  quantity  of  sugar  is  then  produced  in 
the  liver  and  carried  away  from  the  organ  by  the  hepatic  veins ; 
so  that  a  portion  of  it  then  escapes  decomposition  while  passing 
through  the  lungs,  and  begins  to  appear  in  the  blood  of  the  arterial 
system.  Soon  afterward  it  appears  also  in  the  blood  of  the  capil- 
laries; and  from  four  to  six  hours  after  the  commencement  of 
digestion  it  is  produced  in  the  liver  so  much  more  rapidly  than  it 
is  destroyed  in  the  blood,  that  the  surplus  quantity  circulates 
throughout  the  body,  and  the  blood  everywhere  has  a  slightly  sac- 
charine character.  It  does  not,  however,  in  the  healthy  condition, 
make  its  appearance  in  any  of  the  secretions. 

After  the  sixth  hour,  this  unusual  activity  of  the  sugar-producing 
function  begins  again  to  diminish ;  and,  the  transformation  of  the 
sugar  in  the  circulation  going  on  as  before,  it  gradually  disappears 
as  an  ingredient  of  the  blood.  Finally,  the  ordinary  equilibrium 
between  its  production  and  its  decomposition  is  re-established,  and 
it  can  no  longer  be  found  except  in  the  liver  and  in  that  part  of 
the  circulatory  system  which  is  between  the  liver  and  the  lungs. 
There  is,  therefore,  a  periodical  increase  in  the  amount  of  unde- 
composed  sugar  in  the  blood,  as  we  have  already  shown  to  be  the 
case  with  the  fatty  matter  absorbed  during  digestion;  but  this 
increase  is  soon  followed  by  a  corresponding  diminution,  and  during 
the  greater  portion  of  the  time  its  decomposition  keeps  pace  with 
its  production,  and  it  is  consequently  prevented  from  appearing  in 
the  blood  of  the  general  circulation. 

There  are  produced,  accordingly,  in  the  liver,  two  different  secre- 
tions, viz.,  bile  and  sugar.  Both  of  them  originate  by  transforma- 
tion of  the  ingredients  of  the  hepatic  tissue,  from  which  they  are 
absorbed  by  two  different  sets  of  vessels.  The  bile  is  taken  up  by 
the  biliary  ducts,  and  by  them  discharged  into  the  intestine ;  while 
the  sugar  is  carried  off"  by  the  hepatic  veins,  to  be  decomposed  in  the 
circulation,  and  become  subservient  to  the  nutrition  of  the  blood. 


208  THE    SPLEEN. 


CHAPTER  X. 

THE    SPLEEN. 

The  spleen  is  an  exceedingly  vascular  organ,  situated  in  tlie 
vicinity  of  the  great  poucli  of  the  stomach  and  supplied  abund- 
antly by  branches  of  the  cceliac  axis.  Its  veins,  like  those  of  the 
digestive  abdominal  organs,  form  a  part  of  the  great  portal  system, 
and  conduct  the  blood  which  has  passed  through  it  to  the  liver, 
before  it  mingles  again  with  the  general  current  of  the  circulation. 

The  spleen  is  covered  on  its  exterior  by  an  investing  membrane 
or  capsule,  which  forms  a  protective  sac,  containing  the  soft  pulp 
of  which  the  greater  part  of  the  organ  is  composed.  This  capsule, 
in  the  spleen  of  the  ox,  is  thick,  whitish,  and  opaque,  and  is  com- 
posed to  a  great  extent  of  yellow  elastic  tissue.  It  accordingly 
possesses,  in  a  high  degree,  the  physical  property  of  elasticity,  and 
may  be  widely  stretched  without  laceration ;  returning  readily  to 
its  original  size  as  soon  as  the  extending  force  is  relaxed. 

In  the  carnivorous  animals,  on  the  other  hand,  the  capsule  of 
the  spleen  is  thinner,  and  more  colorless  and  transparent.  It  con- 
tains here  but  very  little  elastic  tissue,  being  composed  mostly  of 
smooth,  involuntary  muscular  fibres,  connected  in  layers  by  a  little 
intervening  areolar  tissue.  In  the  herbivorous  animals,  accordingly, 
the  capsule  of  the  spleen  is  simply  elastic,  while  in  the  carnivora  it 
is  contractile. 

In  both  instances,  however,  the  elastic  and  contractile  properties 
of  the  capsule  subserve  a  nearly  similar  purpose.  There  is  every 
reason  to  believe  that  the  spleen  is  subject  to  occasional  and  per- 
haps regular  variations  in  size,  owing  to  the  varying  condition  of 
the  abdominal  circulation.  Dr.  William  Dobson^  found  that  the 
size  of  the  organ  increased,  from  the  third  hour  after  feeding  up  to 
the  fifth ;  when  it  arrived  at  its  maximum,  gradually  decreasing 
after  that  period.     When  these  periodical  congestions  take  place, 

'  In  Gray,  on  the  Structure  and  Uses  of  the  Spleen.     London,  1854,  p.  40. 


THE    SPLEEN".  209 

the  organ  becoming  turgid  with  blood,  the  capsule  is  distended; 
and  limits,  by  its  resisting  power,  the  degree  of  tumefaction  to 
which  the  spleen  is  liable.  When  the  disturbing  cause  has  again 
passed  awaj,  and  the  circulation  is  about  to  return  to  its  ordinary 
condition,  the  elasticity  of  the  capsule  in  the  herbivora,  and  its  con- 
tractility in  the  carnivora,  compress  the  soft  vascular  tissue  within, 
and  reduce  the  organ  to  its  original  dimensions.  This  contractile 
action  of  the  invested  capsule  can  be  readily  seen  in  the  dog  or 
the  cat,  by  opening  the  abdomen  while  digestion  is  going  on, 
exposing  the  spleen  and  removing  it,  after  ligature  of  its  vessels. 
When  first  exposed,  the  organ  is  plump  and  rounded,  and  presents 
externally  a  smooth  and  shining  surface.  But  as  soon  as  it  has 
been  removed  from  the  abdomen  and  its  vessels  divided,  it  begins 
to  contract  sensibly,  becomes  reduced  in  size,  stiff)  and  resisting  to 
the  touch ;  while  its  surface,  at  the  same  time,  becomes  uniformly 
wrinkled,  by  the  contraction  of  its  muscular  fibres. 

In  its  interior,  the  substance  of  the  spleen  is  traversed  everywhere 
by  slender  and  ribbon-like  cords  of  fibrous  tissue,  which  radiate 
from  the  sheath  of  its  principal  arterial  trunks,  and  are  finally 
attached  to  the  internal  surface  of  its  investing  capsule.  These 
fibrous  cords,  or  trabeculse,  as  they  are  called,  by  their  frequent 
branching  and  mutual  interlacement,  form  a  kind  of  skeleton  or 
framework  by  which  the  soft  splenic  pulp  is  embraced,  and  the 
shape  and  integrity  of  the  organ  maintained.  They  are  composed 
of  similar  elements  to  those  of  the  investing  capsule,  viz.,  elastic 
tissue  and  involuntary  muscular  fibres,  united  with  each  other  by 
a  varying  quantity  of  the  fibres  of  areolar  tissue. 

The  interstices  between  the  trabeculse  of  the  spleen  are  occupied 
by  the  splenic  pulp ;  a  soft,  reddish  substance,  which  contains, 
beside  a  few  nerves  and  lymphatics,  capillary  bloodvessels  in  great 
profusion,  and  certain  whitish  globular  bodies,  which  may  be  re- 
garded as  the  distinguishing  anatomical  elements  of  the  organ,  and 
which  are  termed  the  Malpighian  bodies  of  the  spleen. 

The  Malpighian  bodies  are  very  abundant,  and  are  scattered 
throughout  the  splenic  pulp,  being  most  frequently  attached  to  the 
sides,  or  at  the  point  of  bifurcation  of  some  small  artery.  They 
are  readily  visible  to  the  naked  eye  in  the  spleen  of  the  ox,  upon  a 
fresh  section  of  the  organ,  as  minute,  whitish,  rounded  bodies,  which 
may  be  separated,  by  careful  manipulation,  from  the  surrounding 
parts.  In  the  carnivorous  animals,  on  the  other  hand,  and  in  the 
human  subject,  it  is  more  difficult  to  distinguish  them  by  the  un- 
14 


210  THE    SPLEEN. 

aided  eye,  thougli  they  always  exist  in  tlie  spleen  in  a  liealtliy 
condition.  Their  average  diameter,  according  to  Kolliker,  is  ^^^  of 
an  inch.  They  consist  of  a  closed  sac,  or  capsule,  containing  in 
its  interior  a  viscid,  semi-solid  mass  of  cells,  cell-nuclei,  and  homo- 
geneous substance.  Bach  Malpighian  body  is  covered,  on  its  exte- 
rior, by  a  network  of  fine  capillary  bloodvessels ;  and  it  is  now 
perfectly  well  settled,  by  the  observations  of  various  anatomists 
(Kolliker,  Busk,  Huxley,  &c.),  that  bloodvessels  also  penetrate  into 
the  substance  of  the  Malpighian  body,  and  there  form  an  internal 
,  capillary  plexus. 

The  spleen  is  accordingly  a  glandular  organ,  analogous  in  its 
minute  structure  to  the  solitary  and  agminated  glands  of  the  small 
intestine,  and  to  the  lymphatic  glands  throughout  the  body.  Like 
them,  it  is  a  gland  without  an  excretory  duct ;  and  resembles,  also, 
in  this  respect,  the  thyroid  and  thymus  glands  and  the  supra-renal 
capsules.  All  these  organs  have  a  structure  which  is  evidently 
glandular  in  its  nature,  and  yet  the  name  of  glands  has  been  some- 
times refused  to  them  because  they  have,  as  above  mentioned,  no 
duct,  and  produce  apparently  no  distinct  secretion.  We  have 
already  seen,  however,  that  a  secretion  may  be  produced  in  the 
interior  of  a  glandular  organ,  like  the  sugar  in  the  substance  of  the 
liver,  and  yet  not  be  discharged  by  its  excretory  duct.  The  veins 
of  the  gland,  in  this  instance,  perform  the  part  of  excretory  ducts. 
They  absorb  the  new  materials,  and  convey  them,  through  the 
medium  of  the  blood,  to  other  parts  of  the  body,  where  they  suffer 
subsequent  alterations,  and  are  finally  decomposed  in  the  circula- 
tion. 

The  action  of  such  organs  is  consequently  to  modify  the  consti- 
tution of  the  blood.  As  the  blood  passes  through  their  tissue,  it 
absorbs  from  the  glandular  substance  certain  materials  which  it  did 
not  previously  contain,  and  which  are  necessary  to  the  perfect  con- 
stitution of  the  circulating  fluid.  The  blood,  as  it  passes  out  from 
the  organ,  has  therefore  a  different  composition  from  that  which  it 
possessed  before  its  entrance ;  and  on  this  account  the  name  of  vas- 
cular glands  has  been  applied  to  all  the  glandular  organs  above 
mentioned,  which  are  destitute  of  excretory  ducts,  and  is  eminently 
applicable  to  the  spleen. 

The  precise  alteration,  however,  which  is  effected  in  the  blood 
during  its  passage  through  the  splenic  tissue,  has  not  yet  been 
discovered.  Yarious  hypotheses  have  been  advanced  from  time  to 
time,  as  to  the  processes  which  go  on  in  this  organ ;  many  of  them 


THE    SPLEEN.  211 

vague  and  indefinite  in  character,  and  some  of  tliem  directly  con- 
tradictory of  each,  other.  None,  however,  have  yet  been  offered 
which  are  entirely  satisfactory  in  themselves,  or  which  rest  on  suf- 
ficiently reliable  evidence. 

A  very  remarkable  fact  with  regard  to  the  spleen  is  that  it  may 
be  entirely  removed  in  many  of  the  lower  animals,  without  its  loss 
producing  any  serious  permanent  injury.  This  experiment  has 
been  frequently  performed  by  various  observers,  and  we  have  our- 
selves repeated  it  several  times  with  similar  results.  The  organ 
may  be  easily  removed,  in  the  dog  or  the  cat,  by  drawing  it  out  of 
the  abdomen,  through  an  opening  in  the  median  line,  placing  a  few 
ligatures  upon  the  vessels  of  the  gastro-splenic  omentum,  and  then 
dividing  the  vessels  between  the  ligatures  and  the  spleen.  The 
wound  usually  heals  without  difficulty ;  and  if  the  animal  be  killed 
some  weeks  afterward,  the  only  remaining  trace  of  the  operation 
is  an  adhesion  of  the  omentum  to  the  inner  surface  of  the  abdomi- 
nal parietes,  at  the  situation  of  the  original  wound. 

The  most  constant  and  permanent  effect  of  a  removal  of  the 
spleen  is  an  unusual  increase  of  the  appetite.  This  symptom  we 
have  observed  in  some  instances  to  be  excessively  developed ;  so 
that  the  animal  would  at  all  times  throw  himself,  with  a,n  unnatural 
avidity,  upon  any  kind  of  food  offered  him.  We  have  seen  a  dog, 
subjected  to  this  operation,  afterward  feed  without  hesitation  upon 
the  flesh  of  other  dogs ;  and  even  devour  greedily  the  entrails,  taken 
warm  from  the  abdomen  of  the  recently  killed  animal.  The  food 
taken  in  this  unusual  quantity  is,  however,  perfectly  well  digested ; 
and  the  animal  will  often  gain  very  perceptibly  in  weight.  In  one 
instance,  a  cat,  in  whom  the  imnatural  appetite  was  marked  though 
not  excessive,  increased  in  weight  from  five  to  six  pounds,  in  the 
course  of  a  little  less  than  two  months ;  and  at  the  same  time  the 
fur  became  sleek  and  glossy,  and  there  was  a  considerable  improve- 
ment in  the  general  appearance  of  the  animal. 

Another  symptom,  which  usually  follows  removal  of  the  spleen, 
is  an  unnatural  ferocity  of  disposition.  The  animal  will  frequently 
attack  others,  of  its  own  or  a  different  species,  without  any  appa- 
rent cause,  and  without  any  regard  to  the  difference  of  size,  strength, 
&c.  This  symptom  is  sometimes  equally  excessive  with  that  of  an 
unnatural  appetite ;  while  in  other  instances  it  shows  itself  only  in 
occasional  outbursts  of  irritability  and  violence. 

Neither  of  the  symptoms,  however,  which  we  have  just  de- 
scribed, appears  to  exert  any  permanently  injurious  effect  upon  the 


212.  THE    SPLEEN. 

animal  whicli  has  been  subjected  to  the  operation ;  and  life  may  be 
prolonged  for  an  indefinite  period  without  any  serious  disturbance 
of  the  nutritive  process,  after  the  spleen  has  been  completely 
extirpated. 

We  must  accordingly  regard  the  spleen,  not  as  a  single  organ, 
but  as  associated  with  others,  which  may  completely,  or  to  a  great 
extent,  perform  its  functions  after  its  entire  removal.  We  have 
already  noticed  the  similarity  in  structure  between  the  spleen  and 
the  mesenteric  and  lymphatic  glands ;  a  similarity  which  has  led 
some  writers  to  regard  them  as  more  or  less  closely  associated  with 
each  other  in  function,  and  to  consider  the  spleen  as  an  unusually 
developed  lymphatic  or  mesenteric  gland.  It  is  true  that  this 
organ  is  provided  with  a  comparatively  scanty  supply  of  lymphatic 
vessels ;  and  the  chyle,  which  is  absorbed  from  the  intestine,  does 
not  pass  through  the  spleen,  as  it  passes  through  the  remaining 
mesenteric  glands.  Still,  the  physiological  action  of  the  spleen 
may  correspond  with  that  of  the  other  lymphatic  glands,  so  far  as 
regards  its  influence  on  the  blood ;  and  there  can  be  little  doubt 
that  its  function  is  shared,  either  by  them  or  by  some  other  glan- 
dular organs,  which  become  unnaturally  active,  and  more  or  less 
perfectly  supply  its  place  after  its  complete  removal. 


BLOOD-GLOBULES.  213 


CHAPTER  XI. 

THE  BLOOD. 

The  blood,  as  it  exists  in  its  natural  condition,  while  circulating 
in  the  vessels,  is  a  thick  opaque  fluid,  varying  in  color  in  different 
parts  of  the  body  from  a  brilliant  scarlet  to  a  dark  purple.  It  has 
a  slightly  alkaline  reaction,  and  a  specific  gravity  of  1055.  It 
is  not,  however,  an  entirely  homogeneous  fluid,  but  is  found  on 
microscopic  examination  to  consist,  first,  of  a  nearly  colorless, 
transparent,  alkaline  fluid,  termed  the  plasma,  containing  water, 
fibrin,  albumen,  salts,  &c.,  in  a  state  of  mutual  solution;  and, 
secondly,  of  a  large  number  of  distinct  cells,  or  corpuscles,  the 
blood-globules,  swimming  freely  in  the  liquid  plasma.  These  glo> 
bules,  which  are  so  small  as  not  to  be  distinguished  by  the  naked 
eye,  by  being  mixed  thus  abundantly  with  the  fluid  plasma,  give 
to  the  entire  mass  of  the  blood  an  opaque  appearance  and  a  uniform 
red  color. 

Blood-globules. — On  microscopic  examination  it  is  found  that 
the  globules  of  the  blood  are  of  two  kinds,  viz.,  red  and  white ;  of 
these  the  red  are  by  far  the  most  abundant. 

The  red  globules  of  the  blood  present,  under  the  microscope,  a 
perfectly  circular  outline  and  a  smooth  exterior.  (Fig.  54.)  Their 
size  varies  somewhat,  in  human  blood,  even  in  the  same  specimen. 
The  greater  number  of  them  have  a  transverse  diameter  of  ■§  oVo  of 
an  inch ;  but  there  are  many  smaller  ones  to  be  seen,  which  are 
not  more  than  g^V^  o^  even  ^^Vo  of  an  inch  in  diameter.  Their 
form  is  that  of  a  spheroid,  very  much  flattened  on  its  opposite 
surfaces,  somewhat  like  a  round  biscuit,  or  a  thick  piece  of  money 
with  rounded  edges.  The  blood-globule  accordingly,  when  seen 
flatwise,  presents  a  comparatively  broad  surface  and  a  circular  out- 
line (a) ;  but  if  it  be  made  to  roll  over,  it  will  present  itself  edge- 
wise during  its  rotation  and  assume  the  flattened  form  indicated  at 
b.     The  thickness  of  the  globule,  seen  in  this  position,  is  about 


214 


THE    BLOOD. 


Human  Blood-olobules.  —  a.  Red  globules, 
seen  flatwise,  h.  Red  globules,  seen  edgewise,  c. 
White  globule. 


Ts^^o  of  an  inch;  or  a  little  less  than  one-fifth  of  its  transverse 
diameter. 

"When  the  globules  are  examined  lying  upon  their  broad  sur- 
faces, it  can  be  seen  that  these  surfaces  are  not  exactly  flat,  but  that 

there  is  on  each  side  a  slight 
central  depression,  so  that 
the  rounded  edges  of  the 
blood-globule  are  evidently 
thicker  than  its  middle  por- 
tion. This  inequality  pro- 
duces a  remarkable  optical 
effect.  The  substance  of 
which  the  blood-globule  is 
composed  refracts  light  more 
strongly  than  the  fluid  plas- 
ma. Therefore,  when  exa- 
mined with  the  microscope, 
by  transmitted  light,  the 
thick  edges  of  the  globules 
act  as  double  convex  lenses, 
and  concentrate  the  light 
above  the  level  of  the  fluid.  Consequently,  if  the  object-glass  be 
carried  upward  by  the  adjusting  screw  of  the  microscope,  and  lifted 

away  from  the  stage,  so  that 
Fig-  ^^-  the   blood-globules  fall   be- 

yond its  focus,  their  edges 
will  appear  brighter.  But 
the  central  portion  of  each 
globule,  being  excavated  on 
both  sides,  acts  as  a  double 
concave  lens,  and  disperses 
the  light  from  a  point  below 
the  level  of  the  fluid.  It, 
therefore,  grows  brighter  as 
the  object-glass  is  carried 
downward,  and  the  object 
falls  within  its  focus.  An 
alternating  appearance  of  the 
blood-globules  may,  there- 
fore, be  produced  by  view- 
ing them  first  beyond  and  then  within  the  focus  of  the  instrument. 


Red    Globules  of    the  Blood,   seen  a  little 
beyoud  the  focus  of  ttie  microscope. 


BLOOD- GLOBULES, 


215 


The  same,  seeu  a  little  withia  the  focus. 


When  beyond  the  focus,  the  globules  will  be  seen  with  a  bright 
rim  and  a  dark  centre.  (Fig.  55.)  When  within  it  they  will  appear 
with  a  dark  rim  and  a  bright  ^.     ^ , 

"  Fie;.  Sb. 

centre.  (Fig.  56.) 

The  blood-globules  accord- 
ingly have  the  form  of  a 
thickened  disk  with  rounded 
edges  and  a  double  central 
excavation.  They  have,  con- 
sequently, been  sometimes 
called  "  blood-disks,"  instead 
of  blood-globules.  The  term 
'  disk,"  however,  does  not  in- 
dicate their  exact  shape,  any 
more  than  the  other;  and 
the  term  "blood-corpuscle," 
which  is  also  sometimes  used, 
does  not  indicate  it  at  all. 
And  although  the  term  "blood-globule"  may  not  be  precisely  a 
correct  one,  still  it  is  the  most  convenient ;  and  need  not  give  rise 
to  any  confusion,  if  we  remember  the  real  shape  of  the  bodies  de- 
signated by  it.  This  term  will,  consequently,  be  employed  when- 
ever we  have  occasion  to 
speak  of  the  blood-globules  ^^^" 

in  the  following  pages. 

Within  a  minute  after  being 
placed  under  the  microscope, 
the  blood-globules,  after  a 
fluctuating  movement  of 
short  duration,  very  often 
arrange  themselves  in  slight- 
ly curved  rows  or  chains,  in 
•which  they  adhere  to  each 
other  by  their  flat  surfaces, 
presenting  an  appearance 
which  has  been  aptly  com- 
pared with  that  of  rolls  of 
coin.  This  is  probably  ow- 
ing merely  to  the  coagulation 

of  the  blood,  which  takes  place  very  rapidly  when  it  is  spread  out 
in  thin  layers  and  in  contact  with  glass  surfaces ;  and  which,  by 


Blood-globules  adhering  together,  like  rolls 
of  coin. 


216  THE    BLOOD. 

compressing  tlie  globules,  forces  tliem  into  sucli  a  position  tliat  they 
may  occupy  tlie  least  possible  space.  This  position  is  evidently 
that  in  which,  they  are  applied  to  each  other  by  their  flat  surfaces, 
as  above  described. 

The  color  of  the  blood-globules,  when  viewed  by  transmitted 
light  and  spread  out  in  a  thin  layer,  is  a  light  amber  or  pale  yellow. 
It  is,  on  the  contrary,  deep  red  when  they  are  seen  by  reflected 
light,  or  piled  together  in  comparatively  thick  layers.  When  viewed 
singly,  they  are  so  transparent  that  the  outlines  of  those  lying  under- 
neath can  be  easily  seen,  showing  through  the  substance  of  the 
superjacent  globules.  Their  consistency  is  peculiar.  They  are  not 
solid  bodies,  as  they  have  been  sometimes  inadvertently  described ; 
but  on  the  contrary  have  a  consistency  which  is  very  nearly  fluid. 
They  are  in  consequence  exceedingly  flexible,  and  easily  elongated, 
bent,  or  otherwise  distorted  by  accidental  pressure,  or  in  passing 
through  the  narrow  currents  of  fluid  which  often  establish  them- 
selves accidentally  in  a  drop  of  blood  under  microscopic  examina- 
tion. This  distortion,  however,  is  only  temporary,  and  the  globules 
regain  their  original  shape,  as  soon  as  the  accidental  pressure  is 
taken  off.  The  peculiar  flexibility  and  elasticity  thus  noticed  are 
characteristic  of  the  red  globules  of  the  blood,  and  may  always 
serve  to  distinguish  them  from  any  other  free  cells  which  may  be 
found  in  the  animal  tissues  or  fluids. 

In  structure  the  blood-globules  are  homogeneous.  They  have 
been  sometimes  erroneously  described  as  consisting  of  a  closed 
vesicle  or  cell-wall,  containing  in  its  cavity  some  fluid  or  semi-fluid 
substance  of  a  different  character  from  that  composing  the  wall  of 
the  vesicle  itself.  No  such  structure,  however,  is  really  to  be  seen 
in  them.  Each  blood-globule  consists  of  a  mass  of  organized  ani- 
mal substance,  perfectly  or  nearly  homogeneous  in  appearance,  and 
of  the  same  color,  consistency  and  composition  throughout.  In 
some  of  the  lower  animals  (birds,  reptiles,  fish)  it  contains  also  a 
granular  nucleus,  imbedded  in  the  substance  of  the  globule ;  but 
in  no  instance  is  there  any  distinction  to  be  made  out  between  an 
external  cell-wall  and  an  internal  cavity. 

The  appearance  of  the  blood-globules  is  altered  by  the  addition 
of  various  foreign  substances.  If  water  be  added,  so  as  to  dilute 
the  plasma,  the  globules  absorb  it  by  imbibition,  swell,  lose  their 
double  central  concavity  and  become  paler.  If  a  larger  quantity 
of  water  be  added,  they  finally  dissolve  and  disappear  altogether. 
When  a  moderate  quantity  of  water  is  mixed  with  the  blood,  the 


BLOOD-GLOBULES. 


217 


Blood-globules,  swollen  by  the  imbibition  of 
water. 


edges  of  the  globules,  being  thicker  than  the  central  portions,  and 
absorbing  water  more  abundantly,  become  turgid,  and  encroach 
gradually  upon  the   central 

part.     (Fig.  58.)     It  is  very  F'?-  ^^• 

common  to  see  the  central 
depression  under  these  cir- 
cumstances, disappear  on  one 
side  before  it  is  lost  on  the 
other,  so  that  the  globule,  as 
it  swells  up,  curls  over  to- 
wards one  side,  and  assumes 
a  peculiar  cup-shaped  form 
(a).  This  form  may  often  be 
seen  in  blood-globules  that 
have  been  soaking  for  some 
time  in  the  urine,  or  in  any 
other  animal  fluid  of  a  less 
density  than  the  plasma  of 
the  blood.    Dilute  acetic  acid 

dissolves  the  blood-globules  more  promptly  than  water,  and  solu- 
tions of  the  caustic  alkalies  more  promptly  still. 

If  a  drop  of  blood  be  allowed  partially  to  evaporate  while  under 
the  microscope,  the  globules 
near  the  edges  of  the  prepa-  Fig. .  9. 

ration  often  diminish  in  size, 
and  at  the  same  time  present 
a  shrunken  and  crenated  ap- 
pearance, as  if  minute  gran- 
ules were  projecting  from 
their  surfaces  (Fig.  59);  an 
effect  apparently  produced 
by  the  evaporation  of  part 
of  their  watery  ingredients. 
For  some  unexplained  rea- 
son, however,  a  similar  dis- 
tortion is  often  produced  in 
some  of  the  globules  by  the 
addition  of  certain  other  ani- 
mal fluids,  as  for  example  the 

saliva;  and  a  few  can  even  be  seen  in  this  condition  after  the 
addition  of  pure  water. 


Blood-globulks 
crenated. 


shniuken,  with  their  uiari,'ins 


218  THE    BLOOD. 

The  entire  mass  of  the  blood- globules,  in  proportion  to  the  rest 
of  the  circulating  fluid,  can  only  be  approximately  measured  by 
the  eye  in  a  microscopic  examination.  In  ordinary  analyses  the 
globules  are  usually  estimated  as  amounting  to  about  fifteen  per 
cent.,  by  weight,  of  the  entire  blood.  This  estimate,  however,  refers, 
properly  speaking,  not  to  the  globules  themselves,  but  only  to  their 
dry  residue,  after  the  water  which  they  contain  has  been  lost  by 
evaporation.  It  is  easily  seen,  by  examination  with  the  microscope, 
that  the  globules,  in  their  natural  semi-fluid  condition,  are  really 
much  more  abundant  than  this,  and  constitute  fully  one-half  the 
entire  mass  of  the  blood  ;  that  is,  the  intercellular  fluid,  or  plasma,  is 
not  more  abundant  than  the  globules  themselves  which  are  sus- 
pended in  it.  When  separated  from  the  other  ingredients  of  the 
blood  and  examined  by  themselves,  the  globules  are  found,  ac- 
cording to  Lehmann,  to  present  the  following  composition : — 

Composition  of  the  Blood-Globules  in  1000  Parts. 

Wcater 688.00 

Globuline 282.22 

Hffimatine     ...........     16.75 

Fatty  substances  ..........       2.31 

Uodetermined  (extractive)  matters        .         .         .         .         .         .2.60 

Cliloride  of  sodium         ........      •\ 

"  potassium    ........      | 

Phosphates  of  soda  and  potassa    ...... 

Sulphate  "  " j  ^'^^ 

Phosphate  of  lime         ........      i 

"  "  magnesia  .......     J 

1000.00 

The  most  important  of  these  ingredients  is  the  glohuline.  This 
is  an  organic  substance,  nearly  fluid  in  its  natural  condition  by 
union  with  water,  and  constituting  the  greater  part  of  the  mass  of 
the  blood- globules.  It  is  soluble  in  water,  but  insoluble  in  the 
plasma  of  the  blood,  owing  to  the'  presence  in  that  fluid  of  albumen 
and  saline  matters.  If  the  blood  be  largely  diluted,  however,  the 
globuline  is  dissolved,  as  already  mentioned,  and  the  blood-globules 
are  destroyed.  Globuline  coagulates  by  heat ;  but,  according  to 
Eobin  and  Yerdeil,  only  becomes  opalescent  at  160°,  and  requires 
for  its  complete  coagulation  a  temperature  of  200°  F. 

The  hsematine  is  the  coloring  matter  of  the  globules.  It  is,  like 
globuline,  an  organic  substance,  but  is  present  in  much  smaller  quan- 
tity than  the  latter.     It  is  not  contained  in  the  form  of  a  powder, 


BLOOD-GLOBULES. 


219 


mechanically  deposited  in  the  globuline,  but  the  two  substances  are 
intimately  mingled  throughout  the  mass  of  the  blood-globule,  just 
as  the  fibrin  and  albumen  are  mingled  in  the  plasma.  Haematine 
contains,  like  the  other  coloring  matters,  a  small  proportion  of  iron. 
This  iron  has  been  supposed  to  exist  under  the  form  of  an  oxide : 
and  to  contribute  directly  in  this  way  to  the  red  color  of  the  sub- 
stance in  question.  But  it  is  now  ascertained  that  although  the 
iron  is  found  in  an  oxidized  form  in  the  ashes  of  the  blood-globules 
after  they  have  been  destroyed  by  heat,  its  oxidation  probably  takes 
place  during  the  process  of  incineration.  So  far  as  we  know,  there- 
fore, the  iron  exists  originally  in  the  h^matine  as  an  ultimate 
element,  directly  combined  with  the  other  ingredients  of  this  sub- 
stance, in  the  same  manner  as  the  carbon,  the  hydrogen,  or  the 
nitrogen. 

The  blood-globules  of  all  the  warm-blooded  quadrupeds,  with 
the  exception  of  the  family  of  the  camelidse,  resemble  those  of  the 
human  species  in  shape  and  structure.  They  differ,  however,  some- 
what in  size,  being  usually  rather  smaller  than  in  man.  There  are 
but  two  species  in  which  they  are  known  to  be  larger  than  in  man, 
viz.,  the  Indian  elephant,  in  which  they  are  37'oo  of  an  inch,  and 
the  two-toed  sloth  {JBradypus  didadylus),  in  which  they  are  ^gV^  of 
an  inch  in  diameter.  In  the  musk  deer  of  Java  they  are  smaller 
than  in  any  other  known  species,  measuring  rather  less  than  y^^^^ 
of  an  inch.  The  following  is  a  list  showing  the  size  of  the  red 
globules  of  the  blood  in  the  principal  mammalian  species,  taken 
from  the  measurement  of  Mr.  Gulliver.^ 


DiAlIETEK  OF 

Red 

Globules  in  the 

Ape 

-j^'ffgof  an  iuch. 

Cat      . 

4  A  (3  of 

an  inch 

Horse  • 

4555 

Fox     . 

4T'(yir 

Ox 

?2V(I 

Wolf  . 

Je'ffTT 

Sheep  . 

7rg5(y 

Elephant     . 

-t'ott 

Goat     . 

G^Vff 

Red  deer     . 

Saon 

Dog      . 

j:?'fi5 

Musk  deer  . 

jsUu 

In  all  these  instances  the  form  and  general  appearance  of  the 
globules  are  the  same.  The  only  exception  to  this  rule  among  the 
mammalians  is  in  the  family  of  the  camelidse  (camel,  dromedary, 
lama),  in  which  the  globules  present  an  oval  outline  instead  of  a 
circular  one.     In  other  respects  they  resemble  the  foregoing. 

In  the  three  remaining  classes  of  vertebrate  animals,  viz.,  birds, 


•  In  Works  of  William  Hewson,  Sydenham  edition,  London,  1846,  p.  327. 


220 


THE    BLOOD. 


reptiles,  and  fish,  the  blood-globules  differ  so  ranch  from  the  above 
that  they  can  be  readily  distinguished  by  microscopic  examination. 
They  are  oval  in  form,  and  contain  a  colorless  granular  nucleus 
imbedded  in  their  substance.  They  are  also  considerably  larger 
than  the  blood-globules  of  the  mammalians,  particularly  in  the 

class  of  reptiles.  In  the  frog 
(Fig.  60)  they  measure  ja'o^ 
of  an  inch  in  their  long 
diameter;  and  in  Menobran- 
clius,  the  great  water  lizard 
of  the  northern  lakes,  4^0  of 
an  inch.  In  Proteus  angui- 
nus  they  attain  the  size,  ac- 
cording to  Dr.  Carpenter,^  of 
-^\^  of  an  inch. 

Beside  the  corpuscles  de- 
scribed above,  there  are  glo- 
bules of  another  kind  found 
in  the  blood,  viz.,  the  white 
globules.  These  globules  are 
very  much  less  numerous 
than  the  red ;  the  proportion 
between  the  two,  in  human  blood,  being  one  white  to  two  or  three 
hundred  red  globules.  In  reptiles,  the  relative  quantity  of  the 
white  globules  is  greater,  but  they  are  always  considerably  less 
abundant  than  the  red.  They  differ  also  from  the  latter  in  shape, 
size,  color,  and  consistency.  They  are  globular  in  form,  white  or 
colorless,  and  instead  of  being  homogeneous  like  the  others,  their 
substance  is  filled  everywhere  with  minute  dark  molecules,  which 
give  them  a  finely  granular  appearance.  (Fig.  54,  c.)  In  size  they 
are  considerably  larger  than  the  red  globules,  being  about  ^^V^  of 
an  inch  in  diameter.  They  are  also  more  consistent  than  the  others, 
and  do  not  so  easily  glide  along  in  the  minute  currents  of  a  drop  of 
blood  under  examination,  but  adhere  readily  to  the  surfaces  of  the 
glass.  If  treated  with  dilute  acetic  acid,  they  swell  up  and  become 
smooth  and  circular  in  outline ;  and  at  the  same  time  a  separation 
or  partial  coagulation  seems  to  take  place  in  the  substance  of  which 
they  are  composed,  so  that  an  irregular  collection  of  granular 
matter  shows  itself  in  their  interior,  becoming  more  divided  and 


Blood-qlobul  KS  OF  Fkog.— fl.  Blood-globule 
seen  edgewise.    6.  White-globule. 


The  Microscope  and  its  Revelations,  Philadelphia  edition,  p.  600. 


BLOOD-GLOBULES. 


221 


broken  up  as  tlie  action  of  tlie  acetic  acid  upon  tlie  globule  is 
longer  continued.  (Fig.  61.)  This  collection  of  granular  matter 
often  assumes  a  curved  or  crescentic  form,  as  at  a,  and  sometimes 
various  other  irregular  shapes.  It  does  not  indicate  the  existence 
of  a  nucleus  in  the  white  globule,  but  it  is  merely  an  appearance 
produced  by  the  coagulating 

and  disintegrating  action  of  ^l^-  ^^• 

acetic  acid  upon  the  substance 
of  which  it  is  composed. 

The  chemical  constitution 
of  the  white  globules,  as 
distinguished  from  the  red, 
has  never  been  determined ; 
owing  to  the  small  quantity 
in  which  they  occur,  and  the 
difficulty  of  separating  them 
from  the  others  for  purposes 
of  analysis. 

The  two  kinds  of  blood- 
globules,  white  and  red,  are 
to  be  regarded  as  distinct 
and  independent  anatomical 
forms.  It  has  been  sometimes  supposed  that  the  white  globulea 
were  converted,  by  a  gradual  transformation,  into  the  red.  There 
is,  however,  no  direct  evidence  of  this ;  as  the  transformation  has 
never  been  seen  to  take  place,  either  in  the  human  subject  or  in 
the  mammalia,  nor  even  its  intermediate  stages  satisfactorily  ob- 
served. When,  therefore,  in  default  of  any  such  direct  evidence!, 
we  are  reduced  to  the  surmise  which  has  been  adopted  by  some 
authors,  viz.,  that  the  change  "  takes  place  too  rapidly  to  be  de- 
tected by  our  means  of  observation,"^  it  must  be  acknowledged 
that  the  above  opinion  has  no  solid  foundation.  It  has  been  stated 
by  some  authors  (Kolliker,  Gerlach)  that  in  the  blood  of  the 
batrachian  reptiles  there  are  to  be  seen  certain  bodies  intermediate 
in  appearance  between  the  white  and  the  red  globules,  and  which 
represent  different  stages  of  transition  from  one  form  to  the  other ; 
but  this  is  not  a  fact  which  is  generally  acknowledged.  "We  have 
repeatedly  examined,  with  reference  to  this  point,  the  fresh  blood 
of  the  frog,  as  well  as  that  of  the  menobranchus,  in  which  the  large 


White  Globules  of  the  Blood;  altered  by 
dilute  acetic  acid. 


■  Kolliker,  Handbuch  der  Gewebelehre,  Leipzig,  1852,  p.  582, 


222  THE    BLOOD. 

size  of  tlie  globules  would  give  every  opportunity  for  detecting  any 
sucli  changes,  did  they  really  exist ;  and  it  is  our  unavoidable  con- 
clusion from  these  observations,  that  there  is  no  good  evidence,  even 
in  the  blood  of  reptiles,  of  any  such  transformation  taking  place. 
There  is  simply,  as  in  human  blood,  a  certain  variation  in  size  and 
opacity  among  the  red  globules ;  but  no  such  connection  with,  or 
resemblance  to,  the  white  globules  as  to  indicate  a  passage  from  one 
form  to  the  other.  The  red  and  white  globules  are  therefore  to  be 
regarded  as  distinct  and  independent  anatomical  elements.  They 
are  mingled  together  in  the  blood,  just  as  capillary  bloodvessels  and 
nerves  are  mingled  in  areolar  tissue ;  but  there  is  no  other  connection 
between  them,  so  far  as  their  formation  is  concerned,  than  that  of 
juxtaposition. 

Neither  is  it  at  all  probable  that  the  red  globules  are  produced  or 
destroyed  in  any  particular  part  of  the  body.  One  ground  for  the 
belief  that  these  bodies  were  produced  by  a  metamorphosis  of  the 
white  globules  was  a  supposition  that  they  Avere  continually  and 
rapidly  destroyed  somewhere  in  the  circulation ;  and  as  this  loss 
must  be  as  rapidly  counterbalanced  by  the  formation  of  new  glo- 
bules, and  as  no  other  probable  source  of  their  reproduction  ap- 
peared, they  were  supposed  to  be  produced  by  transformation  of 
the  white  globules.  But  there  is  no  reason  for  believing  that  the 
red  globules  of  the  blood  are  any  less  permanent,  as  anatomical 
forms,  than  the  muscular  fibres  or  the  nervous  filaments.  They 
undergo,  it  is  true,  like  all  the  constituent  parts  of  the  body,  a 
constant  interstitial  metamorphosis.  They  absorb  incessantly  nu- 
tritious materials  from  the  blood,  and  give  up  to  the  circulating 
fluid,  at  the  same  time,  other  substances  which  result  from  their 
internal  waste  and  disintegration.  But  they  do  not,  so  far  as  we 
know,  perish  bodily  in  any  part  of  the  circulation.  It  is  not  the 
anatomical  forms,  anywhere,  which  undergo  destruction  and  reno- 
vation in  the  nutritive  process ;  but  only  the  proximate  principles  of 
which  they  are  composed.  The  effect  of  this  interstitial  nutrition, 
therefore,  in  the  blood-globules  as  in  the  various  solid  tissues,  is 
merely  to  maintain  them  in  a  natural  and  healthy  condition  of 
integrity.  Their  ingredients  are  incessantly  altered,  by  transforma- 
tion and  decomposition,  as  they  pass  through  various  parts  of  the 
vasciilar  system;  but  the  globules  themselves  retain  their  form 
and  texture,  and  still  remain  as  constituent  parts  of  the  circulating 
fluid. 


PLASMA. 


223 


Plasma. — The  plasma  of  the  blood,  according  to  Lehmann,  has 
the  following  constitution: — 

COMPOSITIOX  OF  THE  PlASMA  IN  1,000  PAKTS. 

Water 902.90 

Fibrin 4.05 

Albumen 78.84 

Fatty  matters       . 1.72 

Undetermined  (extractive)  matters      ......         3.94 

Chloride  of  sodium      ........       -i 

"  potassium  ....... 

Phosphates  of  soda  and  potassa  .         .         .         .         . 

Sulphates  "  "...... 

Phosphate  of  lime        .         .         .         .         .     '    . 

"  macrnesia         ....... 


8.55 


1000.00 


The  above  ingredients  are  all  intimately  mingled  in  the  blood- 
plasma,  in  a  fluid  form,  by  mutual  solution;  but  they  may  be  sepa- 
rated from  each  other  for  examination  by  appropriate  means.  The 
two  ingredients  belonging  to  the  class  of  organic  substances  are  the 
fibrin  and  the  albumen. 

The  fibrin,  though  present  in  small  quantity,  is  evidently  an  im- 
portant element  in  the  constitution  of  the  blood.  It  may  be  ob- 
tained in  a  tolerably  pure  form  by  gently  stirring  freshly  drawn 
blood  with  a  glass  rod  or  a  bundle  of  twigs ;  upon  which  the  fibrin 
coagulates,  and  adheres  to  the  twigs  in  the  form  of  slender  threads 
and  flakes.  The  fibrin,  thus  coagulated,  is  at  first  colored  red  by 
the  hsematine  of  the  blood-globules  entangled  in  it ;  but  it  may  be 
washed  colorless  by  a  few  hours'  soaking  in  running  water.  The 
fibrin    then    presents   itself 


under  the  form  of  nearly 
white  threads  and  flakes, 
having  a  semi-solid  consist- 
ency, and  a  considerable  de- 
gree of  elasticity. 

The  coagulation  of  fibrin 
takes  place  ^n  a  peculiar 
manner.  It  does  not  solidify 
in  a  perfectly  homogeneous 
mass ;  but  if  examined  by  the 
microscope  in  thin  layers  it 
is  seen  to  have  a  fibroid  or 
filamentous  texture.  In  this 
condition  it  is  said  to  be 
"fibrillated."  (Fig.  62.)    The 


Fig.  62. 


C  ri  A  o  L- 1.  A  T  E  i>  F I B  B I N ,  sho wing  its  flbrillated  cou- 
diciou. 


224  THE    BLOOD. 

filaments  of  whicTi  it  is  composed  are  colorless  and  elastic,  and  when 
isolated  are  seen  to  be  exceedingly  minute,  being  not  more  than 
__!__  or  even  goioo  of  an  inch  in  diameter.  They  are  in  part 
arranged  so  as  to  lie  parallel  with  each  other ;  but  are  more  gene- 
rally interlaced  in  a  kind  of  irregular  network,  crossing  each  other 
in  every  direction.  On  the  addition  of  dilute  acetic  acid,  they  swell 
Tip  and  fuse  together  into  a  homogeneous  mass,  but  do  not  dissolve. 
They  are  often  interspersed  everywhere  with  minute  granular  mole- 
cules, which  render  their  outlines  more  or  less  obscure. 

Once  coagulated,  fibrin  is  insoluble  in  water  and  can  only  be 
again  liquefied  by  the  action  of  an  alkaline  or  strongly  saline  solu- 
tion, or  by  prolonged  boiling  at  a  very  high  temperature.  These 
agents,  however,  produce  a  complete  alteration  in  the  properties  of 
the  fibrin,  and  after  being  subjected  to  them  it  is  no  longer  the 
same  substance  as  before. 

The  quantity  of  fibrin  in  the  blood  varies  in  different  parts  of  the 
body.  According  to  the  observations  of  various  writers,'  there  is 
more  fibrin  generally  in  arterial  than  in  venous  blood.  The  blood 
of  the  veins  near  the  heart,  again,  contains  a  smaller  proportion  of 
fibrin  than  those  at  a  distance.  The  blood  of  the  portal  vein  con- 
tains less  than  that  of  the  jugular ;  and  that  of  the  hepatic  vein  less 
than  that  of  the  portal. 

The  albumen  is  undoubtedly  the  most  important  ingredient  of  the 
plasma,  judging  both  from  its  nature  and  the  abundance  in  which 
it  occurs.  It  coagulates  at  once  on  being  heated  to  160°  F.,  or  by 
contact  with  alcohol,  the  mineral  acids,  the  metallic  salts,  or  with 
ferrocyanide  of  potassium  in  an  acidulated  solution.  It  exists  natu- 
rally in  the  plasma  in  a  fluid  form  by  reason  of  its  union  with 
water.  The  greater  part  of  the  water  of  the  plasma,  in  fact,  is  in 
union  with  the  albumen ;  and  when  the  albumen  coagulates,  the 
water  remains  united  with  it,  and  assumes  at  the  same  time  the 
solid  form.  If  the  plasma  of  the  blood,  therefore,  after  the  removal 
of  the  fibrin,  be  exposed  to  the  temperature  of  160°  F.,  it  solidifies 
almost  completely  ;  so  that  only  a  few  drops  of  water  remain  that 
can  be  drained  away  from  the  coagulated  mass.  The  phosphates 
of  lime  and  magnesia  are  also  held  in  solution  principally  by  the 
albumen,  and  are  retained  by  it  in  coagulation. 

The  fatty  matters  exist  in  the  blood  mostly  in  a  saponified  form, 
excepting  soon  after  the  digestion  of  food  rich  in  fat.  At  that 
period,  as  we  have  already  mentioned,  the  emulsioned  fat  finds  its 

Robin  and  Verdeil,  op.  cit.,  vol.  ii.  p.  202. 


COAGULATION  OF  THE  BLOOD.  225 

way  into  the  blood,  and  circulates  for  a  time  uncaanged.  After- 
ward it  disappears  as  free  fat,  and  remains  partly  in  the  saponified 
condition. 

The  saline  ingredients  of  the  plasma  are  of  the  same  nature  with 
those  existing  in  the  globules.  The  chlorides  of  sodium  and  potas- 
sium, and  the  phosphates  of  soda  and  potassa  are  the  most  abundant 
in  both,  while  the  sulphates  are  present  only  in  minute  quantity. 
The  proportions  in  which  the  various  salts  are  present  are  very  dif- 
ferent, according  to  Lehmann,'  in  the  blood-globules  and  in  the 
plasma.  Chloride  of  potassium  is  most  abundant  in  the  globules, 
chloride  of  sodium  in  the  plasma.  The  phosphates  of  soda  and 
potassa  are  more  abundant  in  the  globules  than  in  the  plasma.  On 
the  other  hand,  the  phosphates  of  lime  and  magnesia  are  more 
abundant  in  the  plasma  than  in  the  globules. 

The  substances  known  under  the  name  o^  extraciive  matters  consist 
of  a  mixture  of  different  ingredients,  belonging  mostly  to  the  class 
of  organic  substances,  which  have  not  yet  been  separated  in  a  state 
of  sufficient  purity  to  admit  of  their  being  thoroughly  examined 
and  distinguished  from  each  other.  They  do  not  exist  in  great 
abundance,  but  are  undoubtedly  of  considerable  importance  in  the 
constitution  of  the  blood.  Beside  the  substances  enumerated  in  the 
above  list,  there  are  still  others  which  occur  in  small  quantity  as 
ingredients  of  the  blood.  Among  the  most  important  are  the  alka- 
line carbonates,  which  are  held  in  solution  in  the  serum.  It  has 
already  been  mentioned  that  while  the  phosphates  are  most  abun- 
dant in  the  blood  of  the  carnivora,  the  carbonates  are  most  abun- 
dant in  that  of  the  herbivora.  Thus  Lehmann'^  found  carbonate  of 
soda  in  the  blood  of  the  ox  in  the  proportion  of  1.628  per  thousand 
parts.  There  are  also  to  be  found,  in  solution  in  the  blood,  urea, 
urate  of  soda,  creatine,  creatinine,  sugar,  &c. ;  all  of  them  crystalliza- 
ble  substances  derived  from  the  transformation  of  other  ingredients 
of  the  blood,  or  of  the  tissues  through  which  it  circulates.  The 
relative  quantity,  however,  of  these  substances  is  very  minute,  and 
has  not  yet  been  determined  with  precision. 

Coagulation  of  the  Blood. — A  few  moments  after  the  blood 
has  been  withdrawn  from  the  vessels,  a  remarkable  phenomenon 
presents  itself,  viz.,  its  coagulation  or  clotting.  This  process  com- 
mences at  nearly  the  same  time  throughout  the  whole  mass  of  the 
blood.     The  blood  becomes  first  somewhat  diminished  in  fluidity, 

'  Op.  cit.,  vol.  i.  p.  540.  2  Op.  cit.,  vol.  i.  p.  393. 

15 


226 


THE    BLOOD. 


SO  that  it  will  not  run  over  tlie  edge  of  the  vessel,  when  slightly 
inclined ;  and  its  surface  may  be  gently  depressed  with  the  end  of 
the  finger  or  a  glass  rod.  It  then  becomes  rapidly  thicker,  and  at 
last  solidifies  into  a  uniformly  red,  opaque,  consistent,  gelatinous 
mass,  which  takes  the  form  of  the  vessel  in  which  the  blood  was 
received.  Its  coagulation  is  then  complete.  The  process  usually 
commences,  in  the  case  of  the  human  subject,  in  about  fifteen  min- 
utes after  the  blood  has  been  drawn,  and  is  completed  in  about 
twenty  minutes. 

The  coagulation  of  the  blood  is  dependent  entirely  upon  the 
presence  of  the  fibrin.  This  fact  has  been  demonstrated  in  various 
ways.  In  the  first  place,  if  frog's  blood  be  filtered,  so  as  to  separate 
the  globules  and  leave  them  upon  the  filter,  while  the  plasma  is 
allowed  to  run  through,  the  colorless  filtered  fluid  which  contains 
the  fibrin  soon  coagulates ;  while  no  coagulation  takes  place  in  the 
moist  globules  remaining  on  the  filter.  Again,  if  the  freshly  drawn 
blood  be  stirred  with  a  bundle  of  rods,  as  we  have  already  de- 
scribed above,  the  fibrin  coagulates  upon  them  by  itself,  while  the 
rest  of  the  plasma,  mixed  with  the  globules,  remains  perfectly  fluid. 
It  is  the  fibrin,  therefore,  which,  by  its  own  coagulation,  induces 
the  solidification  of  the  entire  blood.  As  the  fibrin  is  uniformly 
distributed  throughout  the  blood,  when  its  coagulation  takes  place 
the  minute  filaments  which  make  their  appearance  in  it  entangle 
in  their  meshes  the  globules  and  the  albuminous  fluids  of  the 
plasma.  A  very  small  quantity  of  fibrin,  therefore,  is  sufficient  to 
entangle  by  its  coagulation  all  the  fluid  and  semi-fluid  parts  of  the 
blood,  and  convert  the  whole  into  a  volumi- 
nous, trembling,  jelly-like  mass,  which  is 
known  by  the  name  of  the  "  crassamentum," 
or  "clot."  (Fig.  63.) 

As  soon  as  the  clot  has  fairly  formed,  it 
begins  to  contract  and  diminish  in  size.  Ex- 
actly how  this  contraction  of  the  clot  is  pro- 
duced, we  are  unable  to  say ;  but  it  is  proba- 
bly a  continuation  of  the  same  process  by 
Bowl  of  recently  c  o  a  o  n  -    Avhich  its  solidificatiou  is  at  first  accomplished, 

LATED  Blood,  showing  the     ^^    ^^    j^^g^    ^^^^  ^^j.      gij^Har    tO   it.       As   the 
whole  mass  uniformly  solidi-  -^  .  n    '  ^ 

fied.  contraction  proceeds,  the  albummous  fluids 

begin  to  be  pressed  out  from  the  meshes  in 

which  they  were  entangled.     A  few  isolated  drops  first  appear  on 

the  surface  of  the  clot.     These  drops  soon  increase  in  size  and  be- 


Fig.  63. 


COAGULATION    OF    THE    BLOOD.  227 

come  more  numerous.  They  run  together  and  coalesce  with  each. 
other,  as  more  and  more  fluid  exudes  from  the  coagulated  mass, 
until  the  whole  surface  of  the  clot  is  covered  with  a  thin  layer  of 
fluid.  The  clot  at  first  adheres  pretty  strongly  to  the  sides  of  the 
vessel  into  which  the  blood  was  drawn ;  but  as  its  contraction  goes 
on,  its  edges  are  separated,  and  the  fluid  continues  to  exude  between 
it  and  the  sides  of  the  vessel.  This  exudation 
continues  for  ten  or  twelve  hours ;  the  clot  Fig.  C4. 

growing  constantly  smaller  and  firmer,  and 
the  expressed  fluid  more  and  more  abundant. 
The  globules,  owing  to  their  greater  con- 
sistency, do  not  escape  with  the  albuminous 
fluids,  but  remain  entangled  in  the  fibrinous 
coagulum.     Finally,   at   the  end  of  ten    or 

twelve   hours  the  whole  of  the   blood  has  

usually  separated  into  two  parts,  viz.,  the  clot     ^^^^    ^^    coagulated 
which  is  a  red,  opaque,  dense  and  resisting  blood,  after  twelve  hours: 

^^  r     .  D     ^        r'^      •  i     showing    the    clot    contracted 

semi-solid  mass,  consistmg  ot  the  fibrin  and  and  floating  in  the  fluid  serum, 
the  blood-globules ;  and  the  serum,  which  is  a 

transparent,  nearly  colorless  fluid,  containing  the  water,  albumen 
and  saline  matters  of  the  plasma.  (Fig.  64.) 

The  change  of  the  blood  in  coagulation  may  therefore  be  ex- 
pressed as  follows: — 

Before  coagulation  the  blood  consists  of 

r  Fibrin, 

1st.  Globules:  and  2d.  Plasma — containing  \  ' 

^  j  Water, 

t  Salts. 

After  coagulation  it  is  sepilrated  into 

(Albumen, 
Water, 
Salts. 

The  coagulation  of  the  blood  is  hastened  or  retarded  by  Tarious 
physical  conditions,  which  have  been  studied  with  care  by  various 
observers,  but  more  particularly  by  Robin  and  Verdeil.  The  con- 
ditions which  influence  the  rapidity  of  coagulation  are  as  follows : 
First,  the  rapidity  with  which  the  blood  is  drawn  from  the  vein, 
and  the  size  of  the  orifice  from  which  it  flows.  If  blood  be  drawn 
rapidly,  in  a  full  stream,  from  a  large  orifice,  it  remains  fluid  for  a 
comparatively  long  time;  if  it  be  drawn  slowly,  from  a  narrow 
orifice,  it  coagulates  quickly.  Thus  it  usually  happens  that  in  the 
operation  of  venesection,  the  blood  drawn  immediately  after  the 


228  THE    BLOOD. 

opening  of  tlie  vein  runs  freely  and  coagulates  slowly ;  while  that 
whicli  is  drawn  toward  tlie  end  of  the  operation,  when  the  tension 
of  the  veins  has  been  relieved  and  the  blood  trickles  slowly  from 
the  wound,  coagulates  quickly.  Secondly,  the  shape  of  the  vessel 
into  which  the  blood  is  received  and  the  condition  of  its  internal 
surface.  The  greater  the  extent  of  surface  over  which  the  blood 
comes  in  contact  with  the  vessel,  the  more  is  its  coagulation 
hastened.  Thus,  if  the  blood  be  allowed  to  flow  into  a  tall,  narrow, 
cylindrical  vessel,  or  into  a  shallow  plate,  it  coagulates  more  rapidly 
than  if  it  be  received  into  a  hemispherical  bowl,  in  which  the  ex- 
tent of  surface  is  less,  in  proportion  to  the  entire  quantity  of  blood 
which  it  contains.  For  the  same  reason,  coagulation  takes  place 
more  rapidly  in  a  vessel  with  a  roughened  internal  surface,  than  in 
one  which  is  smooth  and  polished.  The  blood  coagulates  most 
rapidly  when  spread  out  in  thin  layers,  and  entangled  among  the 
fibres  of  cloth  or  sponges.  For  the  same  reason,  also,  hemorrhage 
continues  longer  from  an  incised  wound  than  from  a  lacerated  one ; 
because  the  blood,  in  flowing  over  the  ragged  edges  of  the  lace- 
rated bloodvessels  and  tissues,  solidifies  upon  them  readily,  and  thus 
blocks  up  the  wound. 

In  all  these  cases,  there  is  an  inverse  relation  betAveen  the  rapidity 
of  coagulation  and  the  firmness  of  the  clot.  When  coagulation 
takes  place  slowly,  the  clot  afterward  becomes  small  and  dense,  and 
the  serum  is  abundant.  When  coagulation  is  rapid,  there  is  but 
little  contraction  of  the  coagulum,  an  imperfect  separation  of  the 
serum,  and  the  clot  remains  large,  soft,  and  gelatinous. 

It  is  well  known  to  practical  physicians  that  a  similar  relation 
exists  when  the  coagulation  of  the  blood  is  hastened  or  retarded  by 
disease.  In  cases  of  lingering  and  exhausting  illness,  or  in  diseases 
of  a  typhoid  or  exanthematous  character,  with  much  depression  of 
the  vital  powers,  the  blood  coagulates  rapidly  and  the  clot  remains 
soft.  In  cases  of  active  inflammatory  disease,  as  pleurisy  or  pneu- 
monia, occurring  in  previously  healthy  subjects,  the  blood  coagulates 
slowly,  and  the  clot  becomes  very  firm.  In  every  instance,  the 
blood  which  has  coagulated  liquefies  again  at  the  commencement  of 
putrefaction. 

The  coagulation  of  the  fibrin  is  not  a  commencement  of  organization. 
The  filaments  already  described,  which  show  themselves  in  the  clot 
(Fig.  62),  are  not,  properly  speaking,  organized  fibres,  and  are  en- 
tirely different  in  their  character  from  the  fibres  of  areolar  tissue,  or 
any  other  normal  anatomical  elements.     They  are  simply  the  ulti- 


COAGULATION    OF    THE    BLOOD.  229 

mate  form  which  fibrin  assumes  in  coagulating,  just  as  albumen 
takes  the  form  of  granules  under  the  same  circumstances.  The 
coagulation  of  fibrin  does  not  differ  in  character  from  that  of  any 
other  organic  substance ;  it  merely  differs  in  the  physical  conditions 
which  give  rise  to  it.  All  the  coagulable  organic  substances  are 
naturally  fluid,  and  coagulate  only  when  they  are  placed  under 
certain  unusual  conditions.  But  the  particular  conditions  neces- 
sary for  coagulation  vary  with  the  different  organic  substances. 
Thus  albumen  coagulates  by  the  application  of  heat.  Casein,  which 
is  not  aftected  by  heat,  coagulates  by  contact  with  an  acid  body. 
Pancreatine,  again,  is  coagulated  by  contact  with  sulphate  of  mag- 
nesia, which  has  no  efiect  on  albumen.  So  fibrin,  which  is  naturally 
fluid,  and  which  remains  fluid  so  long  as  it  is  circulating  in  the 
vessels,  coagulates  when  it  is  withdrawn  from  them  and  brought  in 
contact  with  unnatural  surfaces.  Its  coagulation,  therefore,  is  no 
more  "spontaneous,"  properly  speaking,  than  that  of  any  other 
organic  substance.  Still  less  does  it  indicate  anything  like  organ- 
ization, or  even  a  commencement  of  it.  On  the  contrary,  in  the 
natural  process  of  nutrition,  fibrin  is  assimilated  by  the  tissues 
and  takes  part  in  their  organization,  only  when  it  is  absorbed  by 
them  from  the  bloodvessels  in  a  fluid  form.  As  soon  as  it  is  once 
coagulated  by  any  means,  it  passes  into  an  unnatural  condition,  and 
must  be  again  liquefied  and  absorbed  into  the  blood  before  it  can 
be  assimilated. 

As  the  fibrin,  therefore,  is  maintained  in  its  natural  condition  of 
fluidity  by  the  movement  of  the  circulating  blood  in  the  interior  of 
the  vessels,  anything  which  interferes  with  this  circulation  will  in- 
duce its  coagulation.  If  a  ligature  be  placed  upon  an  artery  in  the 
living  subject,  the  blood  which  stagnates  above  the  ligature  coagu- 
lates, just  as  it  would  do  if  entirely  removed  froim  the  circulation. 
If  the  vessel  be  ruptured  or  lacerated,  the  blood  which  escapes  from 
it  into  the  areolar  tissue  coagulates,  because  here  also  it  is  with- 
drawn from  the  circulation.  It  coagulates  also  in  the  interior  of 
the  vessels  after  death  owing  to  the  same  cause,  viz :  stoppage  of 
the  circulation.  During  the  last  moments  of  life,  when  the  flow  of 
blood  through  the  cavities  of  the  heart  is  impeded,  the  fibrin  often 
coagulates,  in  greater  or  less  abundance,  upon  the  moving  chordae 
tendinese  and  the  edges  of  the  valves,  just  as  it  would  do  if  with- 
drawn from  the  body  and  stirred  with  a  bundle  of  twigs.  In  every 
instance,  the  coagulation  of  the  fibrin  is  a  morbid  phenomenon,  de- 
pendent on  the  cessation  or  disturbance  of  the  circulation. 


230 


THE    BLOOD. 


Fig.  65. 


Vertical  section  of  a  Re- 
cent CoAGULUM,  showing 
the  greater  accumulation  of 
blood-globules  at  the  bottom. 


If  the  blood  be  allowed  to  coagulate  in  a  bowl,  and  tbe  clot  be 
then  divided  by  a  vertical  section,  it  will  be  seen  that  its  lower 
portion  is  softer  and  of  a  deeper  red  than  the  upper.  (Fig.  65.) 
This  is  because  the  globules,  which  are  of 
greater  specific  gravity  than  the  plasma,  sink 
toward  the  bottom  of  the  vessel  before  coagu- 
lation takes  place,  and  accumulate  in  the 
lower  portion  of  the  blood.  This  deposit  of 
the  globules,  however,  is  only  partial;  be- 
cause they  are  soon  fixed  and  entangled  by 
the  solid  mass  of  the  coagulum,  and  are  thus 
retained  in  the  position  in  which  they  hap- 
pen to  be  at  the  moment  that  coagulation 
takes  place. 

If  the  coagulation,  however,  be  delayed 
longer  than  usual,  or  if  the  globules  sink  more  rapidly  than  is  cus- 
tomary, they  will  have  time  to  subside  entirely  from  the  upper  por- 
tion of  the  blood,  leaving  a  layer  at  the  surface  which  is  composed 
of  plasma  alone.  When  coagulation  then  takes  place,  this  upper 
portion  solidifies  at  the  same  time  with  the  rest,  and  the  clot  then 
presents  two  different  portions,  viz.,  a  lower  portion  of  a  dark  red 
color,  in  which  the  globules  are  accumulated,  and  an  upper  portion 
from  which  the  globules  have  subsided,  and  which  is  of  a  grayish 
white  color  and  partially  transparent.  This  whitish  layer  on  the 
surface  of  the  clot  is  termed  the  "  buffy  coat ;"  and  the  blood  pre- 
senting it  is  said  to  be  "  buffed."  It  is  an  appearance  which  often 
presents  itself  in  cases  of  acute  inflammatory  disease,  in  which  the 
coagulation  of  the  blood  is  unusually  retarded. 

When  a  clot  with  a  buffy  coat  begins  to  contract,  the  contrac- 
tion takes  place  perfectly  well  in  its  upper 
portion,  but  in  the  lower  part  it  is  impeded 
by  the  presence  of  the  globules  which  have 
accumulated  in  large  quantity  at  the  bottom 
of  the  clot.  While  the  lower  part  of  the 
coagulum,  therefore,  remains  voluminous, 
and  hardly  separates  from  the  sides  of  the 
vessel,  its  upper  colorless  portion  diminishes 
very  much  in  size ;  and  as  its  edges  separate 
from  the  sides  of  the  vessel,  they  curl  over 
toward  each  other,  so  that  the  upper  surface 
of  the  clot  becomes  more  or  less  excavated  or  cup-shaped.  (Fig.  66.) 


Fig.  6S. 


Bowl        of       COAGCLATKD 

Blood,    showing     the    clot 
buffed  and  cupped. 


COAGULATION    OF    THE    BLOOD.  231 

The  blood  is  then  said  to  be  "  buffed  and  cupped."  These  appear- 
ances do  not  present  themselves  under  ordinary  conditions,  but  only 
when  the  blood  has  become  altered  by  disease. 

The  entire  quantity  of  blood  existing  in  the  body  has  never  been 
very  accurately  ascertained.  It  is  not  possible  to  extract  the  whole 
of  it  by  opening  the  large  vessels,  since  a  certain  portion  will  always 
remain  in  the  cavities  of  the  heart,  in  the  veins,  and  in  the  capil- 
laries of  the  head  and  abdominal  organs.  The  other  methods 
which  have  been  practised  or  proposed  from  time  to  time  are  all 
liable  to  some  practical  objection.  We  have  accordingly  only 
been  able  thus  far  to  ascertain  the  minimum  quantity  of  blood 
existing  in  the  body.  Weber  and  Lehmann'  ascertained  as  nearly 
as  possible  the  quantity  of  blood  in  two  criminals  who  suffered 
death  by  decapitation ;  in  both  of  which  cases  they  obtained  essen- 
tially similar  results.  The  body  weighed  before  decapitation  133 
pounds  avoirdupois.  The  blood  which  escaped  from  the  vessels  at 
the  time  of  decapitation  amounted  to  12.27  pounds.  In  order  to 
estimate  the  quantity  of  blood  which  remained  in  the  vessels,  the 
experimenters  then  injected  the  arteries  of  the  head  and  trunk  with 
water,  collected  the  watery  fluid  as  it  escaped  from  the  veins,  and 
ascertained  how  much  solid  matter  it  held  in  solution.  This 
amounted  to  477.22  grains,  which  corresponded  to  4.38  pounds  of 
blood.     The  result  of  the  experiment  is  therefore  as  follows : — 

Blood  which  escaped  from  the  vessels 12.27  pounds. 

"  remained  in  the  body 4.38         " 

Whole  quantity  of  blood  in  the  living  body,  16.65 

The  weight  of  the  blood,  then,  in  proportion  to  the  entire  weight 
of  the  body,  was  as  1  :  8  ;  and  the  body  of  a  healthy  man,  weighing 
140  pounds,  will  therefore  contain  on  the  average  at  least  17| 
pounds  of  blood. 

'  Physiological  Chemistry,  voL  i.  p.  638. 


232  RESPIRATION. 


■  CHAPTER    XII. 

EESPIRATION. 

The  blood  as  it  circulates  in  the  arterial  system  lias  a  bright 
scarlet  color ;  but  as  it  passes  through  the  capillaries  it  gradually 
becomes  darker,  and  on  its  arrival  in  the  veins  its  color  is  a  deep 
purple,  and  in  some  parts  of  the  body  nearly  black.  There  are, 
therefore,  two  kinds  of  blood  in  the  body ;  arterial  blood,  which  is 
of  a  bright  color,  and  venous  blood,  which  is  dark.  Now  it  is  found 
that  the  dark-colored  venous  blood,  which  has  been  contaminated 
by  passing  through  the  capillaries,  is  unfit  for  further  circulation. 
It  is  incapable,  in  this  state,  of  supplying  the  organs  with  their 
healthy  stimulus  and  nutrition,  and  has  become,  on  the  contrary, 
deleterious  and  poisonous.  It  is  accordingly  carried  back  to  the 
heart  by  the  veins,  and  thence  sent  to  the  lungs,  where  it  is  recon- 
verted into  arterial  blood.  The  process  by  which  the  venous  blood 
is  thus  arterialized  and  renovated,  is  known  as  the  process  of 
respiration. 

This  process  takes  place  very  actively  in  the  higher  animals,  and 
probably  does  so  to  a  greater  or  less  extent  in  all  animals  without 
exception.  Its  essential  conditions  are  that  the  circulating  fluid 
should  be  exposed  to  the  influence  of  atmospheric  air,  or  of  an 
aerated  fluid ;  that  is,  of  a  fluid  holding  atmospheric  air  or  oxygen 
in  solution.  The  respiratory  apparatus  consists  essentially  of  a 
moist  and  permeable  animal  membrane,  the  respiratory  membrane, 
with  the  bloodvessels  on  one  side  of  it,  and  the  air  or  aerated  fluid 
on  the  other.  The  blood  and  the  air,  consequently,  do  not  come  in 
direct  contact  with  each  other,  but  absorption  and  exhalation  take 
place  from  one  to  the  other  through  the  thin  membrane  which  lies 
between. 

The  special  anatomical  arrangement  of  the  respiratory  apparatus 
differs  in  different  species  of  animals.  In  most  of  those  inhabiting 
the  water,  the  respiratory  organs  have  the  form  of  gills  or  branchise  ; 
that  is,  delicate   filamentous   prolongations   of  some  part  of  the 


EESPIRATION". 


Head   and    Gills   op    Menobrakchui 


integument  or  mucous  membranes,  wMcli  contain  an  abundant 
supply  of  bloodvessels,  and  which  hang  out  freely  into  the  sur- 
rounding water.  In  many  kinds  of  aquatic  lizards,  as,  for  exam- 
ple, in  menohranchus  (Fig.  67), 

there  are  upon  each  side  of  the  '^'  ^  ' 

neck  three  delicate  feathery 
tufts  of  thread-like  prolonga- 
tions from  the  mucous  mem- 
brane of  the  pharynx,  which 
pass  out  through  fissures  in 
the  side  of  the  neck.  Each 
tuft  is  composed  of  a  prin- 
cipal stem,  upon  which  the 
filaments   are  arranged   in  a 

pinnated  form,  like  the  plume  upon  the  shaft  of  a  feather.  Each 
filament,  when  examined  by  itself,  is  seen  to  consist  of  a  thin,  rib- 
bon-shaped fold  of  mucous  membrane,  in  the  interior  of  which 
there  is  a  plentiful  network  of  minute  bloodvessels.  The  dark 
blood,  as  it  comes  into  the  filament  from  the  branchial  artery,  is 
exposed  to  the  influence  of  the  water  in  which  the  filament  is 
bathed,  and  as  it  circulates  through  the  capillary  network  of  the 
gills  is  reconverted  into  arterial  blood.  It  is  then  carried  away  by 
the  branchial  vein,  and  passes  into  the  general  current  of  the  cir- 
culation. The  apparatus  is  further  supplied  with  a  cartilaginous 
framework,  and  a  set  of  muscles  by  which  the  gills  are  gently  waved 
about  in  the  surrounding  water,  and  constantly  brought  into  con- 
tact with  fresh  portions  of  the  aerated  fluid. 

Most  of  the  aquatic  animals  breathe  by  gills  similar  in  all  their 
essential  characters  to  those  described  above.  In  terrestrial  and 
air-breathing  animals,  however,  the  respiratory  apparatus  is  situated 
internally.  In  them,  the  air  is  made  to  penetrate  into  the  interior 
of  the  body,  into  certain  cavities  or  sacs  called  the  lungs,  which 
are  lined  with  a  vascular  mucous  membrane.  In. the  salamanders, 
for  example,  which,  though  aquatic  in  their  habits,  are  air-breathing 
animals,  the  lungs  are  two  long  cylindrical  sacs,  running  nearly  the 
entire  length  of  the  body,  commencing  anteriorly  by  a  communi- 
cation with  the  pharynx,  and  terminating  by  rounded  extremities 
at  the  posterior  part  of  the  abdomen.  These  lungs,  or  air-sacs, 
have  a  smooth  internal  surface ;  and  the  blood  which  circulates 
through  their  vessels  is  arterialized  by  exposure  to  the  air  contained 
in  their  cavities.     The  air  is  forced  into  the  lungs  by  a  kind  of 


234 


BESPIRATION". 


Fiff.   68. 


swallowing  movement,  and  is  after  a  time  regurgitated  and  dis- 
charged, in  order  to  make  room  for  a  fresh  supply. 

In  frogs,  turtles,  serpents,  &c.,  the  structure  of  the  lung  is  a 
little  more  complicated,  since  respiration  is  more  active  in  these 
animals,  and  a  more  perfect  organ  is  requisite  to  accomplish  the 
arterialization  of  the  blood.  In  these  animals,  the  cavity  of  the 
lung,  instead  of  being  simple,  is  divided  by  incomplete  partitions 
into  a  number  of  smaller  cavities  or  "  cells."  The  cells  all  commu- 
nicate with  the  central  pulmonary  cavity ;  and  the  partitions,  which 
join  each  other  at  various  angles,  are  all  composed  of  thin,  pro- 
jecting folds  of  the  lining  membrane,  with  bloodvessels  ramifying 
between  them.  (Fig.  68.)  By  this  arrangement, 
the  extent  of  surface  presented  to  the  air  by  the 
pulmonary  membrane  is  much  increased,  and  the 
arterialization  of  the  blood  takes  place  with  a 
corresponding  degree  of  rapidity. 

In  the  human  subject,  and  in  all  the  warm- 
blooded quadrupeds,  the  lungs  are  constructed 
on  a  plan  which  is  essentially  similar  to  the 
above,  and  which  difi'ers  from  it  only  in  the 
greater  extent  to  which  the  pulmonary  cavity  is 
subdivided,  and  the  surface  of  the  respiratory 
membrane  increased.  The  respiratory  apparatus 
(Fig.  69)  commences  with  the  larynx,  which 
communicates  with  the  pharynx  at  the  upper  part  of  the  neck. 
Then  follows  the  trachea,  a  membranous  tube  with  cartilaginous 
rings ;  which,  upon  its  entrance  into  the  chest,  divides  into  the  right 
and  left  bronchus.  These  again  divide  successively  into  secondary 
and  tertiary  bronchi ;  the  subdivision  continuing,  while  the  bron- 
chial tubes  grow  smaller  and  more  numerous,  and  separate  con- 
stantly from  each  other.  As  they  diminish  in  size,  the  tubes  grow 
more  delicate  in  structure,  and  the  cartilaginous  rings  and  plates 
disappear  from  their  walls.  They  are  finally  reduced,  according  to 
Kolliker,  to  the  size  of  5'^  of  an  inch  in  diameter ;  and  are  com- 
posed only  of  a  thin  mucous  membrane,  lined  with  pavement  epi- 
thelium, which  rests  upon  an  elastic  fibrous  layer.  They  are  then 
known  as  the  "  ultimate  bronchial  tubes." 

Each  ultimate  bronchial  tube  terminates  in  a  division  or  islet  of 
the  pulmonary  tissue,  about  tV  of  an  inch  in  diameter,  which  is 
termed  a  "  pulmonary  lobule."  Each  pulmonary  lobule  resembles 
m  its  structure  the  entire  froo^'s  lung  in  miniature.     It  consists  of  a 


LuNo  oe  Frog, 
eh  owing  its  internal  sur- 
face. 


RESPIRATION", 
Fipr.  69. 


235 


Human  Larynx,  Trachea,    Bronchi,  and  Lungs;  showing  che  ramification  of  the 
bronchi,  and  the  division  of  the  lungs  into  lobules. 

vascular  membrane  inclosing  a  cavitj;  whicli  cavity  is  divided 
into  a  large  number  of  secondary  compartments  by  thin  septa  or 
partitions,  whicb  project  from  its  internal  surface.  (Fig.  70.)  These 
secondary  cavities  are  the  "pulmonary 
cells,"  or  "  vesicles."  Each  vesicle  is  about 
T^\  of  an  inch  in  diameter ;  and  is  covered 
on  its  exterior  with  a  close  network  of  ca- 
pillary bloodvessels,  which  dip  down  into 
the  spaces  between  the  adjacent  vesicles,  and 
expose  in  this  way  a  double  surface  to  the 
air  which  is  contained  in  their  cavities. 
Between  the  vesicles,  and  in  the  interstices 
between  the  lobules,  there  is  a  large  quan- 
tity of  yellow  elastic  tissue,  which  gives 
firmness  and  resiliency  to  the  pulmonary 
structure.     The  pulmonary  vesicles,  accord- 

,        ,1  ^  ■•  o    ■Tr^^^T^  Sinoi,  eLobuleofHu- 

mr^  to  the   observations   of  Kolliker,  are    „^«  luno-^,  ultimate  bron- 
lined  everywhere  with  a  layer  of  pavement    "hiai  tube.  h.  cavity  of  lobuie. 

,■,■,.  .  -11  •  1  c,c,c.  Pulmonary  cells,  or  vesi- 

epithelium,  continuous   with   that   m   the     cies. 


236  EESPIRATION. 

■ultimate  broncliial  tubes.  The  whole  extent  of  respiratory  sur- 
face in  both  lungs  has  been  calculated  by  Lieberkiihn^  at  fourteen 
hundred  square  feet.  It  is  plainly  impossible  to  make  a  precisely 
accurate  calculation  of  this  extent;  but  there  is  every  reason  to 
believe  that  the  estimate  adopted  by  Lieberkiihn,  regarded  as 
approximative,  is  not  by  any  means  an  exaggerated  one.  The 
great  multiplication  of  the  minute  pulmonary  vesicles,  and  of  the 
partitions  between  them,  must  evidently  increase  to  an  extraor- 
dinary degree  the  extent  of  surface  over  which  the  blood,  spread 
out  in  a  thin  layer,  is  exposed  to  the  action  of  the  air.  These 
anatomical  conditions  are,  therefore,  the  most  favorable  for  its  rapid 
and  complete  arterialization. 

Eespiratoey  Movements  of  the  Chest. — The  air  which  is  con- 
tained in  the  pulmonary  lobules  and  vesicles  becomes  rapidly  vitiated 
in  the  process  of  respiration,  and  requires  therefore  to  be  expelled 
and  replaced  by  a  fresh  supply.  This  exchange  or  renovation  of 
the  air  is  effected  by  alternate  movements  of  the  chest,  of  expansion 
and  collapse,  which  are  termed  the  "respiratory  movements  of  the 
chest."  The  expansion  of  the  chest  is  effected  by  two  sets  of  mus- 
cles, viz.,  first,  the  diaphragm,  and,  second,  the  intercostals.  While 
the  diaphragm  is  in  a  state  of  relaxation,  it  has  the  form  of  a  vaulted 
partition  between  the  thorax  and  abdomen,  the  edges  of  which  are 
attached  to  the  inferior  extremity  of  the  sternum,  the  inferior 
costal  cartilages,  the  borders  of  the  lower  ribs  and  the  bodies  of 
the  lumbar  vertebrae,  while  its  convexity  rises  high  into  the  cavity 
of  the  chest,  as  far  as  the  level  of  the  fifth  rib.  When  the  fibres 
of  the  diaphragm  contract,  their  curvature  is  necessarily  dimi- 
nished ;  and  they  approximate  a  straight  line,  exactly  in  proportion 
to  the  extent  of  their  contraction.  Consequently,  the  entire  con- 
vexity of  the  diaphragm  is  diminished  in  the  same  proportion, 
and  it  descends  toward  the  abdomen,  enlarging  the  cavity  of  the 
chest  from  above  downward.  (Fig.  71.)  At  the  same  time  the  inter- 
costal muscles  enlarge  it  in  a  lateral  direction.  For  the  ribs,  arti- 
culated behind  with  the  bodies  of  the  vertebrae,  and  joined  in  front 
to  the  sternum  by  the  flexible  and  elastic  costal  cartilages,  are  so 
arranged  that,  in  a  position  of  rest,  their  convexities  look  obliquely 
outward  and  downward.  When  the  movement  of  inspiration  is 
about  to  commence,  the  first  rib  is  fixed  by  the  contraction  of  the 

'  In  Simon's  Chemistrj  of  Man,  Philada.  ed.,  1846,  p.  109. 


RESPIRATORY    MOVEMENTS    OF    THE    CHEST. 


Fig.  71. 


scaleni  muscles,  and  the  intercostal  muscles  then  contracting  simul- 
taneously, the  ribs  are  drawn  upward.  In  this  movement,  as  each 
rib  rotates  upon  its  articulation  with  the 
spinal  column  at  one  extremity,  and  with 
the  sternum  at  the  other,  its  convexity  is 
necessarily  carried  outward  at  the  same 
time  that  it  is  drawn  upward,  and  the  pa- 
rietes  of  the  chest  are,  therefore,  expanded 
laterally.  The  sternum  itself  rises  slightly 
with  the  same  movement,  and  enlarges  to 
some  extent  the  antero-posterior  diameter 
of  the  thorax.  By  the  simultaneous  action, 
therefore,  of  the  diaphragm  which  descends, 
and  of  the  intercostal  muscles  which  lift 
the  ribs  and  the  sternum,  the  cavity  of  the 
chest  is  expanded  in  every  direction,  and 
the  air  passes  inward,  through  the  trachea 
and  bronchial  tubes,  by  the  simple  force  of 
aspiration. 

After  the  movement  of  inspiration  is  ac- 
complished, and  the  lungs  are  filled  with 
air,  the  diaphragm  and  intercostal  muscles 
relax,  and  a  movement  of  expiration  takes 
place,  by  which  the  chest  is  partially  col- 
lapsed, and  a  portion  of  the  air  contained 
in  the  pulmonary  cavity  expelled.  The 
movement  of  expiration  is  entirely  a  passive 
one,  and  is  accomplished  by  the  action  of 
three  different  forces.  First,  the  abdominal 
organs,  which  have  been  pushed  out  of  their 
usual  position  by  the  descent  of  the  diaphragm,  fall  backward  by 
their  own  weight  and  carry  upward  the  relaxed  diaphragm  before 
them.  Secondly,  the  costal  cartilages,  which  are  slightly  twisted 
out  of  shape  when  the  ribs  are  drawn  upward,  resume  their  natural 
position  as  soon  as  the  muscles  are  relaxed,  and,  drawing  the  ribs 
down  again,  compress  the  sides  of  the  chest.  Thirdly,  the  pul- 
monary tissue,  as  we  have  already  remarked,  is  abundantly  sup- 
plied with  yellow  elastic  fibres,  which  retract  by  virtue  of  their 
own  elasticity,  in  every  part  of  the  lungs,  after  they  have  been 
forcibly  distended,  and,  compressing  the  pulmonary  vesicles,  drive 
out  a  portion  of  the  air  which  they  contained.     By  the  constant 


DiAORAM  ILLtrSTRATIXa 
THE  KeSPIRATORT  MOVE- 
MENTS.—  a.  Cavity  of  the  chest. 
b.  Diaphragm.  The  dark  out- 
lines show  the  figure  of  the  chest 
when  collapsed  ;  the  dotted  lines 
show  the  same  when  expanded. 


238  RESPIRATION". 

recurrence  of  these  alternating  movements  of  inspiration  and  expi- 
ration, fresli  portions  of  air  are  constantly  introduced  into  and 
expelled  from  the  chest. 

The  average  quantity  of  atmospheric  air,  taken  into  and  dis- 
charged from  the  lungs  with  each  respiratory  movement,  is,  ac- 
cording to  the  results  of  various  observers,  twenty  cubic  inches.  At 
eighteen  respirations  per  minute,  this  amounts  to  360  cubic  inches 
of  air  inspired  per  minute,  21,600  cubic  inches  per  hour,  and  518,400 
cubic  inches  per  day.  But  as  the  movements  of  respiration  are 
increased  both  in  extent  and  rapidity  by  every  muscular  exertion, 
the  entire  quantity  of  air  daily  used  in  respiration  is  not  less  than 
600,000  cubic  inches,  or  350  cubic  feet. 

The  whole  of  the  air  in  the  chest,  however,  is  not  changed  at  each 
movement  of  respiration.  On  the  contrary,  a  very  considerable 
quantity  remains  in  the  pulmonary  cavity  after  the  most  complete 
expiration  ;  and  even  after  the  lungs  have  been  removed  from  the 
chest,  they  still  contain  a  large  quantity  of  air  which  cannot  be 
entirely  displaced  by  any  violence  short  of  disintegrating  and  dis- 
organizing the  pulmonary  tissue.  It  is  evident,  therefore,  that  only 
a  comparatively  small  portion  of  the  air  in  the  lungs  passes  in  and 
out  with  each  respiratory  movement ;  and  it  will  require  several 
successive  respirations  before  all  the  air  in  the  chest  can  be  entirely 
changed.  It  has  not  been  possible  to  ascertain  with  certainty  the 
exact  proportion  in  volume  which  exists  between  the  air  which  is 
alternately  inspired  and  expired,  or  ''tidal"  air,  and  that  which 
remains  constantly  in  the  chest,  or  "  residual"  air,  as  it  is  called. 
It  has  been  estimated,  however,  by  Dr.  Carpenter,^  from  the  reports 
of  various  observers,  that  the  volume  of  inspired  and  expired  air 
varies  from  10  to  13  per  cent,  of  the  entire  quantity  contained  in 
the  chest.  If  this  estimate  be  correct,  it  will  require  from  eight  to 
ten  respirations  to  change  the  whole  quantity  of  air  in  the  cavity 
of  the  chest. 

"  It  is  evident,  however,  from  the  foregoing,  that  the  inspiratory 
and  expiratory  movements  of  the  chest  cannot  be  sufficient  to 
change  the  air  at  all  in  the  pulmonary  lobules  and  vesicles.  The 
air  which  is  drawn  in  with  each  inspiration  penetrates  only  into 
the  trachea  and  bronchial  tubes,  until  it  occupies  the  place  of  that 
which  was  driven  out  by  the  last  expiration.  By  the  ordinary 
respiratory  movements,  therefore,  only  that  small  portion  of  the 

'  Human  Physiology,  PLilada.  ed.,  1855,  p.  300. 


RESPIRATORY    MOVEMENTS    OF    THE    GLOTTIS.  239 

air  lying  nearest  the  exterior,  in  the  trachea  and  large  bronchi, 
would  fluctuate  backward  and  forward,  without  ever  penetrating 
into  the  deeper  parts  of  the  lung,  were  there  no  other  means  pro- 
vided for  its  renovation.  There  are,  however,  two  other  forces  in 
play  for  this  purpose.  The  first  of  these  is  the  diffusive  power  of 
the  gases  themselves.  The  air  remaining  in  the  deeper  parts  of 
the  chest  is  richer  in  carbonic  acid  and  poorer  in  oxygen  than  that 
which  has  been  recently  inspired ;  and  by  the  laws  of  gaseous  dif- 
fusion there  must  be  a  constant  interchange  of  these  gases  between 
the  pulmonary  vesicles  and  the  trachea,  tending  to  mix  them 
equally  in  all  parts  of  the  lung.  This  mutual  diffusion  and  inter- 
mixture of  the  gases  will  therefore  tend  to  renovate,  partially  at 
least,  the  air  in  the  pulmonary  lobules  and  vesicles.  Secondly,  the 
trachea  and  bronchial  tubes,  down  to  those  even  of  the  smallest 
size,  are  lined  with  a  mucous  membrane  which  is  covered  with 
ciliated  epithelium.  The  movement  of  those  cilia  is  found  to  be 
directed  always  from  below  upward;  and,  like  ciliary  motion 
wherever  it  occurs,  it  has  the  effect  of  producing  a  current  in  tlie 
same  direction,  in  the  fluids  covering  the  mucous  membrane.  The 
air  in  the  tubes  must  partici- 
pate, to  a  certain  extent,  in  Fig.  72. 
this  current,  and  a  double 
stream  of  air  therefore  is  estab- 
lished in  each  bronchial  tube ; 
one  current  passing  from  with- 
in outward  along  the  walls  of 
the  tube,  and  a  return  current 
passing  from  without  inward, 

.  Small  Bronchial  Tube,  showing  outward 

along    tne    central     part    OI     its        and  inward  current,  produced  by  ciliary  motion. 

cavity.      (Fig.    72.)      By  this 

means  a  kind  of  aerial  circulation  is  constantly  maintained  in  the 
interior  of  the  bronchial  tubes ;  which,  combined  with  the  mutual 
diffusion  of  the  gases  and  the  alternate  expansion  and  collapse  of 
the  chest,  effectually  accomplishes  the  renovation  of  the  air  contained 
in  all  parts  of  the  pulmonary  cavity. 

Respiratory  Movements  of  the  Glottis. — Beside  the  move, 
ments  of  expansion  and  collapse  already  described,  belonging  to 
the  chest,  there  are  similar  respiratory  movements  which  take  place 
in  the  larynx.  If  the  respiratory  passages  be  examined  after  death, 
in  the  state  of  collapse  in  which  they  are  usually  found,  it  will  be 


210 


RESPIRATION 


noticed  that  the  opening  of  the  glottis  is  very  much  smaller  than 
the  cavity  of  the  trachea  below.  The  glottis  itself  presents  the 
appearance  of  a  narrow  chink,  while  the  passage  for  the  inspired 
air  widens  in  the  lower  part  of  the  larynx,  and  in  the  trachea 
constitutes  a  spacious  tube,  nearly  cylindrical  in  shape,  and  over 
half  an  inch  in  diameter.  We  have  found,  for  instance,  that  in 
the  human  subject  the  space  included  between  the  vocal  chords 
has  an  area  of  only  0.15  to  0.17  square  inch ;  while  the  calibre 
of  the  trachea  in  the  middle  of  its  length  is  0.45  square  inch. 
This  disproportion,  however,  which  is  so  evident  after  death,  does 
not  exist  during  life.  While  respiration  is  going  on,  there  is  a 
constant  and  regular  movement  of  the  vocal  chords,  synchronous 
with  the  inspiratory  and  expiratory  movements  of  the  chest,  by 


Fig. 


■pis.  74. 


Human  Larynx,  viewpd  from  above 
ia  its  ordinary  post-mortem  coQdition. — a. 
Vocal  chords,  b.  Thyroid  cartilage,  cc.  Ary- 
tenoid cartilages.  0.  Opening  of  theglottis. 


The  i^ame,  with  the  glottis  openpil  hy 
separation  of  the  vocal  chords. — a.  Vocal 
chords.  6.  Thyroid  cartilage,  cc.  Aryte- 
noid cartilages,    o.  Opening  of  the  glottis. 


which  the  size  of  the  glottis  is  alternately  enlarged  and  diminished. 
At  every  inspiration,  the  glottis  opens  and  allows  the  air  to  pass 
freely  into  the  trachea ;  at  every  expiration  it  collapses,  and  the 
air  is  driven  out  through  it  from  below.  These  movements  are 
called  the  "  respiratory  movements  of  the  glottis."  They  correspond 
in  every  respect  with  those  of  the  chest,  and  are  excited  or  retarded 
by  similar  causes.  AVhenever  the  general  movements  of  respiration 
are  hurried  and  labored,  those  of  the  glottis  become  accelerated  and 
increased  in  intensity  at  the  same  time  ;  and  when  the  movements 
of  the  chest  are  slower  or  fainter  than  usual,  owing  to  debility, 
coma,  or  the  like,  those  of  the  glottis  are  diminished  in  the  same 
proportion. 


CHANGES    IN    THE    AIR    DURING    RESPIRATION. 


241 


Fig.75. 


In  the  respiratory  motions  of  tlie  glottis,  as  in  those  of  the  chest, 
the  movement  of  inspiration  is  an  active  one,  and  that  of  expira- 
tion passive.  In  inspiration,  the  glottis 
is  opened  by  contraction  of  the  posterior 
crico-arytenoid  muscles.  (Fig.  75.) 
These  muscles  originate  from  the  pos- 
terior surface  of  the  cricoid  cartilage, 
near  the  median  line ;  and  their  fibres, 
running  upward  and  outward,  are  in- 
serted into  the  external  angle  of  the 
arytenoid  cartilages.  By  the  contrac- 
tion of  these  muscles,  during  the  move- 
ment of  inspiration,  the  arytenoid  car- 
tilages are  rotated  upon  their  articula- 
tions with  the  cricoid,  so  that  their 
anterior  extremities  are  carried  outward, 
and  the  vocal  chords  stretched  and  sepa- 
rate from  each  other.  (Fig.  74.)  In  this 
way,  the  size  of  the  glottis  may  be  in- 
creased from  0.15  to  0.27  square  inch. 

In  expiration,   the  posterior   crico- 
arytenoid muscles  are  relaxed,  and  the  elasticity  of  the  vocal  chords 
brings  them  back  to  their  former  position. 

The  motions  of  respiration  consist,  therefore,  of  two  sets  of  move- 
ments: viz.,  those  of  the  chest  and  those  of  the  glottis.  These  move- 
ments, in  the  natural  condition,  correspond  with  each  other  both  in 
time  and  intensity.  It  is  at  the  same  time  and  by  the  same  nervous 
influence,  that  the  chest  expands  to  inhale  the  air,  while  the  glottis 
opens  to  admit  it ;  and  in  expiration,  the  muscles  of  both  chest  and 
glottis  are  relaxed ;  while  the  elasticity  of  the  tissues,  by  a  kind  of 
passive  contraction,  restores  the  parts  to  their  original  condition. 


HpMAN  Larynx,  postertor 
VIEW. — a.  Thyroid  cartilage,  b.  EpW 
glottis,  cc.  Arytenoid  cartilages,  d. 
Cricoid  cartilage,  ee.  Posterior  crico« 
arytenoid  muscles.    /.  Trachea. 


Changes  in  the  Air  during  Eespiration. — The  atmospheric 
air,  as  it  is  drawn  into  the  cavity  of  the  lungs,  is  a  mixture  of  oxy- 
gen and  nitrogen,  in  the  proportion  of  about  21  per  cent.,  by  volume, 
of  oxygen,  to  79  per  cent,  of  nitrogen.  It  also  contains  about  one- 
twentieth  per  cent,  of  carbonic  acid,  a  varying  quantity  of  watery 
vapor,  and  some  traces  of  ammonia.  The  last  named  ingredients, 
however,  are  quite  insignificant  in  comparison  with  the  oxygen  and 
nitrogen,  which  form  the  principal  parts  of  its  mass. 

If  collected  and  examined,  after  passing  through  the  lungs,  the 
16 


242  RESPIKATION. 

air  is  found  to  have  become  altered  in  the  following  essential  par- 
ticulars, viz : — 

1st.  It  has  lost  oxygen. 

2d.  It  has  gained  carbonic  acid.     And 

3d.  It  has  absorbed  the  vapor  of  water. 

Beside  the  two  latter  substances,  there  are  also  exhaled  with  the 
expired  air  a  very  small  quantity  of  nitrogen,  over  and  above  what 
was  taken  in  with  inspiration,  and  a  little  animal  matter  in  a 
gaseous  form,  which  communicates  a  slight  but  peculiar  odor  to 
the  breath.  The  air  is  also  somewhat  elevated  in  temperature,  by 
contact  with  the  pulmonary  mucous  membrane. 

The  watery  vapor,  which  is  exhaled  with  the  breath,  is  given  off 
by  the  pulmonary  mucous  membrane,  by  which  it  is  absorbed  from 
the  blood.  At  ordinary  temperatures  it  is  transparent  and  invisi- 
ble ;  but  in  cold  weather  it  becomes  partly  condensed,  on  leaving 
the  lungs,  and  appears  under  the  form  of  a  cloudy  vapor  discharged 
with  the  breath.  According  to  the  researches  of  Yalentin,  the 
average  quantity  of  water,  exhaled  daily  from  the  lungs,  is  8100 
grains,  or  about  1^  pounds  avoirdupois. 

By  far  the  most  important  part,  however,  of  the  changes  suffered 
by  the  air  in  respiration,  consists  in  its  loss  of  oxygen,  and  its 
absorption  of  carbonic  acid. 

According  to  the  researches  of  Yalentin,  Vierordt,  Eegnault  and 
Reiset,  &c.,  the  air  loses  during  respiration,  on  an  average,  five  per 
cent,  of  its  volume  of  oxygen.  At  each  inspiration,  therefore, 
about  one  cubic  inch  of  oxygen  is  removed  from  the  air  and  ab- 
sorbed by  the  blood ;  and  as  we  have  seen  that  the  entire  daily 
quantity  of  air  used  in  respiration  is  about  350  cubic  feet,  the  entire 
quantity  of  oxygen  thus  consumed  in  twenty-four  hours  is  not  less 
than  seventeen  and  a  half  cubic  feet.  This  is,  by  weight,  7,134 
grains,  or  a  little  over  one  pound  avoirdupois. 

The  oxygen  which  thus  disappears  from  the  inspired  air  is  not 
entirely  replaced  in  the  carbonic  acid  exhaled ;  that  is,  there  is  less 
oxygen  in  the  carbonic  acid  which  is  returned  to  the  air  by  expira- 
tion than  has  been  lost  during  inspiration. 

There  is  even  more  oxygen  absorbed  than  is  given  off  again  in 
both  the  carbonic  acid  and  aqueous  vapor  together,  which  are 
exhaled  from  the  lungs.^  There  is,  then,  a  constant  disappearance 
of  oxygen  from  the  air  used  in  respiration,  and  a  constant  accumu- 
lation of  carbonic  acid. 

'  Lehmaim's  Physiological  Chemistry,  Philada.  ed.,  vol.  ii.  p.  432. 


CHANGES    IN    THE    BLOOD    DURING    RESPIRATION.      243 

The  proportion  of  oxygen  whicli  disappears  in  the  interior  of  the 
body,  over  and  above  that  which  is  returned  in  the  breath  under 
the  form  of  carbonic  acid,  varies  in  different  kinds  of  animals.  In 
the  herbivora,  it  is  about  10  per  cent,  of  the  whole  amount  of  oxy- 
gen inspired ;  in  the  carnivora,  20  or  25  per  cent,  and  even  more. 
It  is  a  very  remarkable  fact,  also,  and  an  important  one,  as  regards 
the  theory  of  respiration,  that,  in  the  same  animal,  the  proportion  of 
oxygen  absorbed,  to  that  of  carbonic  acid  exhaled,  varies  according 
to  the  quality  of  the  food.  In  dogs,  for  instance,  while  fed  on  ani- 
mal food,  according  to  the  experiments  of  Regnault  and  Reiset,  25 
per  cent,  of  the  inspired  oxj^gen  disappeared  in  the  body  of  the 
animal;  but  when  fed  on  starchy  substances,  all  but  8  per  cent, 
reappeared  in  the  expired  carbonic  acid.  It  is  already  evident, 
therefore,  from  these  facts,  that  the  oxygen  of  the  inspired  air  is 
not  altogether  employed  in  the  formation  of  carbonic  acid. 

Changes  in  the  Blood  during  Respiration. — If  we  pass  from 
the  consideration  of  the  changes  produced  in  the  air  by  respiration 
to  those  which  take  place  in  the  blood  during  the  same  process,  we 
find,  as  might  have  been  expected,  that  the  latter  correspond 
inversely  with  the  former.  The  blood,  in  passing  through  the 
lungs,  suffers  the  following  alterations : — 

1st.  Its  color  is  changed  from  venous  to  arterial. 

2d.  It  absorbs  oxygen.     And 

3d.  It  exhales  carbonic  acid  and  the  vapor  of  water. 

The  interchange  of  gases,  which  takes  place  during  respiration 
between  the  air  and  the  blood,  is  a  simple  phenomenon  of  absorp- 
tion and  exhalation.  The  inspired  oxygen  does  not,  as  Lavoisier 
once  supposed,  immediately  combine  with  carbon  in  the  lungs,  and 
return  to  the  atmosphere  under  the  form  of  carbonic  acid.  On  the 
contrary,  almost  the  first  fact  of  importance  which  has  been  estab- 
lished by  the  examination  of  the  blood  in  this  respect  is  the  fol- 
lowing, viz :  that  carbonic  acid  exists  ready  formed  in  the  venous  blood 
before  its  entrance  into  the  lungs ;  and,  on  the  other  hand,  that  the 
oxygen  which  is  absorbed  during  respiration  passes  off  in  a  free  state 
with  the  arterial  blood.  The  real  process,  as  it  takes  place  in  the 
lung,  is,  therefore,  for  the  most  part,  as  follows :  The  blood  comes  to 
the  lungs  already  charged  with  carbonic  acid.  In  passing  through 
the  pulmonary  capillaries,  it  is  exposed  to  the  influence  of  the  air 
in  the  cavity  of  the  pulmonary  cells,  and  a  transudation  of  gases 
takes  place  through  the    moist   animal   membranes  of  the  lung. 


244:  RESPIRATION. 

Since  the  blood  in  the  capillaries  contains  a  larger  proportion  of 
carbonic  acid  than  the  air  in  the  air- vesicles,  a  portion  of  this  gas 
leaves  the  blood  and  passes  out  through  the  pulmonary  membrane; 
while  the  oxygen,  being  more  abundant  in  the  air  of  the  vesicles 
than  in  the  circulating  fluid,  passes  inward  at  the  same  time,  and  is 
condensed  by  the  blood. 

In  this  double  phenomenon  of  exhalation  and  absorption,  which 
takes  place  in  the  lungs,  both  parts  of  the  process  are  equally 
necessary  to  life.  It  is  essential  for  the  constant  activity  and  nutri- 
tion of  the  tissues  that  they  be  steadily  supplied  with  oxygen  by  the 
blood ;  and  if  this  supply  be  cut  off,  their  functional  activity  ceases. 
On  the  other  hand,  the  carbonic  acid  which  is  produced  in  the  body 
by  the  processes  of  nutrition  becomes  a  poisonous  substance,  if  it 
be  allowed  to  collect  in  large  quantity.  Under  ordinary  circum- 
stances, the  carbonic  acid  is  removed  by  exhalation  through  the 
lungs  as  fast  as  it  is  produced  in  the  interior  of  the  body ;  but  if 
respiration  be  suspended,  or  seriously  impeded,  since  the  production 
of  carbonic  acid  continues,  while  its  elimination  is  prevented,  it 
accumulates  in  the  blood  and  in  the  tissues,  and  terminates  life  in  a 
few  moments,  by  a  rapid  deterioration  of  the  circulating  fluid,  and 
more  particularly  by  its  poisonous  effect  on  the  nervous  system. 

The  deleterious  effects  of  breathing  in  a  confined  space  will 
therefore  very  soon  become  apparent.  As  respiration  goes  on,  the 
oxygen  of  the  air  constantly  diminishes,  and  the  carbonic  acid, 
mingled  with  it  by  exhalation,  increases  in  quantity.  After  a  time 
the  air  becomes  accordingly  so  poor  in  oxygen  that,  by  that  fact 
alone,  it  is  incapable  of  supporting  life.  At  the  same  time,  the 
carbonic  acid  becomes  so  abundant  in  the  air  vesicles  that  it  pre- 
vents the  escape  of  that  which  already  exists  in  the  blood ;  and  the 
deleterious  effect  of  its  accumulation  in  the  circulating  fluid  is 
added  to  that  produced  by  a  diminished  supply  of  oxygen.  An 
increased  proportion  of  carbonic  acid  in  the  atmosphere  is  therefore 
injurious  in  a  similar  manner,  although  there  may  be  no  diminution 
of  oxygen ;  since  by  its  presence  it  impedes  the  elimination  of  the 
carbonic  acid  already  formed  in  the  blood,  and  induces  the  poison- 
ous effects  which  result  from  its  accumulation. 

Examination  of  the  blood  shows  furthermore  that  the  interchange 
of  gases  in  the  lungs  is  not  complete  but  only  partial  in  its  extent. 
It  results  from  the  experiments  of  Magendie,  Ma,gnus,  and  others, 
that  both  oxygen  and  carbonic  acid  are  contained  in  both  venous 


CHANGES    IN    THE    BLOOD    DURING    RESPIRATION,      245 

and  arterial  blood.  Magnus^  found  that  the  proportion  of  oxygen 
to  carbonic  acid,  by  volume,  in  arterial  blood  was  as  10  to  25 ;  in 
venous  blood  as  10  to  40.  The  venous  blood,  then,  as  it  arrives  at 
the  lungs,  still  retains  a  remnant  of  the  oxygen  which  it  had  pre- 
viously absorbed ;  and  in  passing  through  the  pulmonary  capil- 
laries it  gives  off  only  a  part  of  the  carbonic  acid  with  which  it  has 
become  charged  in  the  general  circulation. 

The  oxygen  and  carbonic  acid  of  the  blood  exist  in  a  state  of 
solution  in  the  circulating  fluid,  and  not  in  a  state  of  intimate  chemi- 
cal combination.  This  is  shown  by  the  fact  that  both  of  these 
substances  may  be  withdrawn  from  the  blood  by  simple  exhaustion 
with  an  air-pump,  or  by  a  stream  of  any  other  indifferent  gas,  such 
as  hydrogen,  which  possesses  sufficient  physical  displacing  power. 
Magnus  found^  that  freshly  drawn  arterial  blood  yielded  by  simple 
agitation  with  carbonic  acid  more  than  10  per  cent,  of  its  volume 
of  oxygen.  The  carbonic  acid  may  also  be  expelled  from  venous 
blood  by  a  current  of  pure  oxygen,  or  of  hydrogen,  or,  in  great 
measure,  by  simple  agitation  with  atmospheric  air.  There  is  some 
difficulty  in  determining,  however,  whether  the  carbonic  acid  of 
the  blood  be  altogether  in  a  free  state,  or  whether  it  be  partly  in  a 
state  of  loose  chemical  combination  with  a  base,  under  the  form  of 
an  alkaline  bicarbonate.  A  solution  of  bicarbonate  of  soda  itself 
will  lose  a  portion  of  its  carbonic  acid,  and  become  reduced  to  the 
condition  of  a  carbonate  by  simple  exhaustion  under  the  air-pump, 
or  by  agitation  with  pure  hydrogen  at  the  temperature  of  the  body. 
Lehmann  has  found^  that  after  the  expulsion  of  all  the  carbonic 
acid  removable  by  the  air-pump  and  a  current  of  hydrogen,  there 
still  remains,  in  ox's  blood,  0.1628  per  cent,  of  carbonate  of  soda ; 
and  he  estimates  that  this  quantity  is  sufficient  to  have  retained  all 
the  carbonic  acid,  previously  given  off,  in  the  form  of  a  bicarbonate. 
It  makes  little  or  no  difference,  however,  so  far  as  regards  the  pro- 
cess of  respiration,  whether  the  carbonic  acid  of  the  blood  exist  in 
an  entirely  free  state,  or  under  the  form  of  an  alkaline  bicarbonate ; 
since  it  may  be  readily  removed  from  this  combination,  at  the  tem- 
perature of  the  body,  by  contact  with  an  indifferent  gas. 

The  oxygen  and  carbonic  acid  of  the  blood  are  in  solution  prin- 
cipally in  the  hhod-glohules,  and  not  in  the  plasma.  The  researches 
of  Magnus  have  shown"  that  the  blood  holds  in  solution  2|  times 

'  In  Lehmann,  op.  cit.,  vol.  i.  p.  570. 

2  In  Robin  and  Verdf'il,  op.  cit.,  vol.  ii.  p.  34. 

3  Op.  cit.,  vol   i.  p.  393. 

*  In  Robin  and  Verdeil,  op.  cit.,  vol.  ii.  pp.  28—32. 


246  RESPIRATION. 

as  mucli  oxygen  as  pure  water  could  dissolve  at  tlie  same  tempera- 
ture ;  and  that  "while  the  serum  of  the  blood,  separated  from  the 
globules,  exerts  no  more  solvent  power  on  oxygen  than  pure  water, 
defibrinated  blood,  that  is,  the  serum  and  globules  mixed,  dissolves 
quite  as  much  oxygen  as  the  fresh  blood  itself.  The  same  thing  is 
true  with  regard  to  the  carbonic  acid.  It  is  therefore  the  semi- 
fluid blood-globules  which  retain  these  two  gases  in  solution ;  and 
since  the  color  of  the  blood  depends  entirely  upon  that  of  the  glo- 
bules, it  is  easy  to  understand  why  the  blood  should  alter  its  hue 
from  purple  to  scarlet  in  passing  through  the  lungs,  where  the 
globules  give  up  carbonic  acid,  and  absorb  a  fresh  quantity  of 
oxygen.  The  above  change  may  readily  be  produced  outside  the 
body.  If  freshly  drawn  venous  blood  be  shaken  in  a  bottle  with 
pure  oxygen,  its  color  changes  at  once  from  purple  to  red ;  and  the 
same  change  will  take  place,  though  more  slowly,  if  the  blood  be 
simply  agitated  with  atmospheric  air.  It  is  for  this  reason  that  the 
surface  of  defibrinated  venous  blood,  and  the  external  parts  of  a 
dark-colored  clot,  exposed  to  the  atmosphere,  become  rapidly  red- 
dened, while  the  internal  portions  retain  their  original  color. 

The  process  of  respiration,  so  far  as  we  have  considered  it,  con- 
sists in  an  alternate  interchange  of  carbonic  acid  and  oxygen  in  the 
blood  of  the  general  and  pulmonary  circulations.  In  the  pulmonary 
circulation,  carbonic  acid  is  given  off  and  oxygen  absorbed ;  while 
in  the  general  circulation  the  oxygen  gradually  disappears,  and  is 
replaced,  in  the  venous  blood,  by  carbonic  acid.  The  oxygen  which 
thus  disappears  from  the  blood  in  the  general  circulation  does  not, 
for  the  most  part,  enter  into  direct  combination  in  the  blood  itself. 
On  the  contrary,  it  exists  there,  as  we  have  already  stated,  in  the 
form  of  a  simple  solution.  It  is  absorbed,  however,  from  the  blood 
of  the  capillary  vessels,  and  becomes  fixed  in  the  substance  of  the 
vascular  tissues.  The  blood  may  be  regarded,  therefore,  in  this 
respect,  as  a  circulating  fluid,  destined  to  transport  oxygen  from  the 
lungs  to  the  tissues ;  for  it  is  the  tissues  themselves  which  finally 
appropriate  the  oxygen,  and  fix  it  in  their  substance. 

The  next  important  question  which  presents  itself  in  the  study 
of  the  respiratory  process  relates  to  the  origin  of  the  carbonic  acid  in 
the  venous  blood.  It  was  formerly  supposed,  when  Lavoisier  first 
discovered  the  changes  produced  in  the  air  by  respiration,  that  the 
production  of  the  carbonic  acid  could  be  accounted  for  in  a  very 
simple  manner.     It  was  thought  to  be  produced  in  the  lungs  by  a 


CHANGES    IN    THE    BLOOD    DURING    RESPIRATION.      247 

direct  union  of  the  inspired  oxygen  with  the  carbon  of  the  blood 
in  the  pulmonary  vessels.  It  was  found  afterward,  however,  that 
this  could  not  be  the  case ;  since  carbonic  acid  exists  already  formed 
in  the  blood,  previously  to  its  entrance  into  the  lungs.  It  was  then 
imagined  that  the  oxidation  of  carbon,  and  the  consequent  produc- 
tion of  carbonic  acid,  took  place  in  the  capillaries  of  the  general 
circulation,  since  it  could  not  be  shown  to  take  place  in  the  lungs, 
nor  between  the  lungs  and  the  capillaries.  The  truth  is,  however, 
that  no  direct  evidence  exists  of  such  a  direct  oxidation  taking 
place  anywhere.  The  formation  of  carbonic  acid,  as  it  is  now 
understood,  takes  place  in  three  different  modes :  1st,  in  the  lungs ; 
2d,  in  the  blood ;  and  3d,  in  the  tissues. 

First,  in  the  lungs.  There  exists  in  the  pulmonary  tissue  a  pecu- 
liar acid  substance,  first  described  by  VerdeiP  under  the  name  of 
"  pneumie"  or  "  pulmonic"  acid.  It  is  a  crystallizable  body,  soluble 
in  water,  which  is  produced  in  the  substance  of  the  pulmonary 
tissue  by  transformation  of  some  of  its  other  ingredients,  in  the 
same  manner  as  sugar  is  produced  in  the  tissue  of  the  liver.  It  is 
on  account  of  the  presence  of  this  substance  that  the  fresh  tissue  of 
the  lung  has  usually  an  acid  reaction  to  test-paper,  and  that  it  has 
also  the  property,  which  has  been  noticed  by  several  observers,  of 
decomposing  the  metallic  cyanides,  with  the  production  of  hydro- 
cyanic acid ;  a  property  not  possessed  by  sections  of  areolar  tissue, 
the  internal  surface  of  the  skin,  &c.  &c.  When  the  blood,  there- 
fore, comes  in  contact  with  the  pulmonary  tissue,  which  is 
permeated  everywhere  by  pneumie  acid  in  a  soluble  form,  its 
alkaline  carbonates  and  bicarbonates,  if  any  be  present,  are  decom- 
posed with  the  production  on  the  one  hand  of  the  pneumates  of 
soda  and  potassa,  and  on  the  other  of  free  carbonic  acid,  which  is 
exhaled.  M.  Bernard  has  found*  that  if  a  solution  of  bicarbonate 
of  soda  be  rapidly  injected  into  the  jugular  vein  of  a  rabbit,  it 
becomes  decomposed  in  the  lungs  with  so  rapid  a  development  of 
carbonic  acid,  that  the  gas  accumulates  in  the  pulmonary  tissue, 
and  even  in  the  pulmonary  vessels  and  the  cavities  of  the  heart,  to 
such  an  extent  as  to  cause  immediate  death  by  stoppage  of  the 
circulation.  In  the  normal  condition,  however,  the  carbonates  and 
bicarbonates  of  the  blood  arrive  so  slowly  at  the  lungs  that  as  fast 
as  they  are  decomposed  there,  the  carbonic  acid  is  readily  exhaled 
by  expiration,  and  produces  no  deleterious  effect  on  the  circulation. 

'  Robin  and  Verdeil,  op.  cit.,  vol.  ii.  p.  460. 
*  Archives  Gen.  de  Med.,  xvi.  222. 


218  RESPIRATION, 

Secondly,  in  the  hlood.  There  is  little  doubt,  althougli  the  fact  has 
not  been  directly  proved,  that  some  of  the  oxygen  definitely  dis- 
appears, and  some  of  the  carbonic  acid  is  also  formed,  in  the  sub- 
stance of  the  blood-globules  during  their  circulation.  Since  these 
globules  are  anatomical  elements,  and  since  they  undoubtedly  go 
through  with  nutritive  processes  analogous  to  those  which  take 
place  in  the  elements  of  the  solid  tissues,  there  is  every  reason  for 
believing  that  they  also  require  oxygen  for  their  support,  and  that 
they  produce  carbonic  acid  as  one  of  the  results  of  their  interstitial 
decomposition.  While  the  oxygen  and  carbonic  acid,  therefore, 
contained  in  the  globules,  are  for  the  most  part  transported  by 
these  bodies  from  the  lungs  to  the  tissues,  and  from  the  tissues  back 
again  to  the  lungs,  they  probably  take  part,  also,  to  a  certain  extent, 
in  the  nutrition  of  the  blood-globules  themselves. 

Thirdly,  in  the  tissues.  This  is  by  far  the  most  important  source 
of  the  carbonic  acid  in  the  blood.  From  the  experiments  of  Spal- 
lanzani,  W.  Edwards,  Marchand  and  others,  the  following  very 
important  fact  has  been  established,  viz.,  that  every  organized  tissue 
and  even  every  organic  substance,  when  in  a  recent  condition,  has  the 
power  of  absorbing  oxygen  and  of  exhaling  carbonic  acid.  Gr.  Liebig, 
for  example, '  found  that  frog's  muscles,  recently  prepared  and  com- 
pletely freed  from  blood,  continued  to  absorb  oxygen  and  discharge 
carbonic  acid.  Similar  experiments  with  other  tissues  have  led 
to  a  similar  result.  The  interchange  of  gases,  therefore,  in  the 
process  of  respiration,  takes  place  mostly  in  the  tissues  themselves. 
It  is  in  their  substance  that  the  oxygen  becomes  fixed  and  assimi- 
lated, and  that  the  carbonic  acid  takes  its  origin.  As  the  blood  in 
the  lungs  gives  up  its  carbonic  acid  to  the  air,  and  absorbs  oxygen 
from  it,  so  in  the  general  circulation  it  gives  up  its  oxygen  to  the 
tissues,  and  absorbs  from  them  carbonic  acid. 

We  come  lastly  to  examine  the  exact  mode  by  which  the  car- 
bonic acid  originates  in  the  animal  tissues.  Investigation  shows 
that  even  here  it  is  not  produced  by  a  process  of  oxidation,  or  direct 
union  of  oxygen  with  the  carbon  of  the  tissues,  but  in  some  other  and  more 
indirect  mode.  This  is  proved  by  the  fact  that  animals  and  fresh 
animal  tissues  will  continue  to  exhale  carbonic  acid  in  an  atmo- 
sphere of  hydrogen  or  of  nitrogen,  or  even  when  placed  in  a  vacuum. 
Marchand  found''  that  frogs  would  live  for  from  half  an  hour  to  an 
hour  in  pure  hydrogen  gas ;  and  that  during  this  time  they  exhaled 
even  more  carbonic  acid  than  in  atmospheric  air,  owing  probably 
'  In  Lehmann,  op.  cit.,  vol.  ii.  p.  474.  *  Ibid.,  p.  442. 


CHANGES    IN    THE    BLOOD    DURING    RESPIRATION.      249 

to  the  superior  displacing  power  of  hydrogen  for  carbonic  acid. 
For  while  15,500  grains'  weight  of  frogs  exhaled  about  1.13  grain 
of  carbonic  acid  per  hour  in  atmospheric  air,  they  exhaled  during 
the  same  time  in  pure  hydrogen  as  much  as  4.07  grains.  The  same 
observer  found  that  frogs  would  recover  on  the  admission  of  air 
after  remaining  for  nearly  half  an  hour  in  a  nearly  complete 
vacuum ;  and  that  if  they  were  killed  by  total  abstraction  of  the 
air,  15,500  grains'  weight  of  the  animals  were  found  to  have 
eliminated  9.3  grains  of  carbonic  acid.  The  exhalation  of  carbonic 
acid  by  the  tissues  does  not,  therefore,  depend  directly  upon  the 
access  of  free  oxygen.  It  cannot  go  on,  it  is  true,  for  an  indefinite 
time,  any  more  than  the  other  vital  processes,  without  the  presence 
of  oxygen.  But  it  may  continue  long  enough  to  show  that  the 
carbonic  acid  exhaled  is  not  a  direct  product  of  oxidation,  but  that 
it  originates,  on  the  contrary,  in  all  probability,  by  a  decomposi- 
tion of  the  organic  ingredients  of  the  tissues,  resulting  in  the  pro- 
duction of  carbonic  acid  on  the  one  hand,  and  of  various  other 
substances  on  the  other,  with  which  we  are  not  yet  fully  acquainted ; 
in  very  much  the  same  manner  as  the  decomposition  of  sugar 
during  fermentation  gives  rise  to  alcohol  on  the  one  hand  and  to 
carbonic  acid  on  the  other.  The  fermentation  of  sugar,  when  it  has 
once  commenced,  does  not  require  the  continued  access  of  air.  It 
will  go  on  in  an  atmosphere  of  hydrogen,  or  even  when  confined  in 
a  close  vessel  over  mercury ;  since  its  carbonic  acid  is  not  produced 
by  direct  oxidation,  but  by  a  decomposition  of  the  sugar  already 
present.  For  the  same  reason,  carbonic  acid  will  continue  to  be 
exhaled  by  living  or  recently  dead  animal  tissues,  even  in  an  atmo- 
sphere of  hydrogen,  or  in  a  vacuum. 

Carbonic  acid  makes  its  appearance,  accordingly,  in  the  tissues,, 
as  one  product  of  their  decomposition  in  the  nutritive  process. 
From  them  it  is  taken  up  by  the  blood,  either  in  simple  solution  or 
in  loose  combination  as  a  bicarbonate,  transported  by  the  circulation 
to  the  lungs,  and  finally  exhaled  from  the  pulmonary  mucous  mem^ 
brane  in  a  gaseous  form. 

The  carbonic  acid  exhaled  from  the  lungs  should  accordingly  be 
studied  by  itself  as  one  of  the  products  of  the  animal  organism,  and 
its  quantity  ascertained  in  the  different  physiological  conditions  of 
the  body.  The  expired  air  usually  contains  about  four  per  cent,  of 
its  volume  of  carbonic  acid.  According  to  the  researches  of  Vier- 
ordt,'  which  are  regarded  as  the  most  accurate  on  this  subject,  an 
'  In  Lehmann,  op.  cit.,  vol.  ii.  p.  439. 


250  KESPIRATION. 

adult  man  gives  oft'  1.62  cubic  inch  of  carbonic  acid  with  each  nor- 
mal expiration.  This  amounts  to  very  nearly  1,150  cubic  inches 
per  hour,  or  fifteen  and  a  half  cubic  feet  per  day.  This  quantity 
is,  by  weight,  10,740  grains,  or  a  little  over  one  pound  and  a  half. 
The  amount  of  carbonic  acid  exhaled,  however,  varies  from  time  to 
time,  according  to  many  different  circumstances ;  so  that  no  such 
estimate  can  represent  correctly  its  quantity  at  all  times.  These 
variations  have  been  very  fully  investigated  by  Andral  and  Gavar- 
ret,'  who  found  that  the  principal  conditions  modifying  the  amount 
of  this  gas  produced  were  age,  sex,  constitution  and  development. 
The  variations  were  very  marked  in  different  individuals,  notwith- 
standing that  the  experiments  were  made  at  the  same  period  of  the 
day,  and  with  the  subject  as  nearly  as  possible  in  the  same  condi- 
tion. Thus  they  found  that  the  quantity  of  carbonic  acid  exhaled 
per  hour  in  five  different  individuals  was  as  follows : — 

Quantity  of  Cakbonic  Acid  pee  houk. 
In  subject  No.  1 1207  cubic  inches. 


970 
1250 
1250 
1591 


"With  regard  to  the  difference  produced  by  age,  it  was  found  that 
from  the  period  of  eight  years  up  to  puberty  the  quantity  of  car- 
bonic acid  increases  constantly  with  the  age.  Thus  a  boy  of  eight 
years  exhales,  on  the  average,  564  cubic  inches  per  hour ;  while  a 
boy  of  fifteen  years  exhales  981  cubic  inches  in  the  same  time. 
Boys  exhale  during  this  period  more  carbonic  acid  than  girls  of  the 
same  age.  In  males  this  augmentation  of  the  quantity  of  carbonic 
acid  continues  till  the  twenty-fifth  or  thirtieth  year,  when  it  reaches, 
on  the  average,  1398  cubic  inches  per  hour.  Its  quantity  then 
remains  stationary  for  ten  or  fifteen  years ;  then  diminishes  slightly 
from  the  fortieth  to  the  sixtieth  year ;  and  after  sixty  years  dimi- 
nishes in  a  marked  degree,  so  that  it  may  fall  so  low  as  1038  cubic 
inches.  In  one  superannuated  person,  102  years  of  age,  Andral 
and  Gavarret  found  the  hourly  quantity  of  carbonic  acid  to  be 
only  665  cubic  inches. 

In  women,  the  increase  of  carbonic  acid  ceases  at  the  period  of 
puberty ;  and  its  production  then  remains  constant  until  the  cessa- 
tion of  menstruation,  about  the  fortieth  or  forty-fifth  year.  At  that 
time  it  increases  again  until  after  fifty  years,  when  it  subsequently 

1  Annales  de  Chimie  et  de  Pharmacia,  1843,  vol.  viii.  p.  129. 


CHANGES    IN    THE    BLOOD    DURING    RESPIKATION.      251 

diminislies  with  the  approach  of  old  age,  as  in  men.  Pregnancy, 
occurring  at  anj  time  in  the  above  period,  immediately  produces  a 
temporary  increase  in  the  quantity  of  carbonic  acid. 

The  strength  of  the  constitution,  and  more  particularly  the  deve- 
lopment of  the  muscular  system,  was  found  to  have  a  very  great  in- 
fluence in  this  respect ;  increasing  the  quantity  of  carbonic  acid 
very  much  in  proportion  to  the  weight  of  the  individual.  The 
largest  production  of  carbonic  acid  observed  was  in  a  young  man, 
26  years  of  age,  whose  frame  presented  a  remarkably  vigorous  and 
athletic  development,  and  who  exhaled  1591  cubic  inches  per  hour. 
This  large  quantity  of  carbonic  acid,  moreover,  in  well  developed 
persons,  is  not  owing  simply  to  the  size  of  the  entire  body,  but 
particularly  to  the  development  of  the  muscular  system,  since  an 
unusually  large  skeleton,  or  an  abundant  deposit  of  adipose  tissue, 
is  not  accompanied  by  any  such  increase  of  the  carbonic  acid. 

Andral  and  Gavarret  finally  sum  up  the  results  of  their  investiga- 
tions as  follows : — 

1.  The  quantity  of  carbonic  acid  exhaled  from  the  lungs  in  a  given 
time  varies  with  the  age,  the  sex,  and  the  constitution  of  the  subject. 

2.  In  the  male,  as  well  as  in  the  female,  the  quantity  of  carbonic 
acid  varies  according  to  the  age ;  and  that  independently  of  the 
weight  of  the  individual  subjected  to  experiment. 

3.  During  all  the  periods  of  life,  from  that  of  eight  years  up  to 
the  most  advanced  age,  the  male  and  female  may  be  distinguished 
by  the  different  quantities  of  carbonic  acid  which  they  exhale  in  a 
given  time.  Other  things  being  equal,  the  male  exhales  always  a 
larger  quantity  than  the  female.  This  difference  is  particularly 
marked  between  the  ages  of  16  and  40  years,  during  which  period 
the  male  usually  exhales  twice  as  much  carbonic  acid  as  the  female. 

4.  In  the  male,  the  quantity  of  carbonic  acid  increases  constantly 
from  eight  to  thirty  years ;  and  the  rate  of  this  increase  undergoes 
a  rapid  augmentation  at  the  period  of  puberty.  Beyond  thirty 
years  the  exhalation  of  carbonic  acid  begins  to  decrease,  and  its 
diminution  is  more  marked  as  the  individual  approaches  extreme 
old  age,  so  that  near  the  termination  of  life,  the  quantity  of  carbonic 
acid  produced  may  be  no  greater  than  at  the  age  of  ten  years. 

5.  In  the  female,  the  exhalation  of  carbonic  acid  increases  accord- 
ing to  the  same  law  as  in  the  male,  from  the  age  of  eight  years 
until  puberty.  But  at  the  period  of  puberty,  at  the  same  time  with 
the  appearance  of  menstruation,  the  exhalation  of  carbonic  acid. 


252  EESPIRATION. 

contrary  to  what  happens  in  the  male,  ceases  to  increase ;  and  it 
afterward  remains  stationary  so  long  as  the  menstrual  periods  recur 
with  regularity.  At  the  cessation  of  the  menses,  the  quantity  of 
carbonic  acid  exhaled  increases  in  a  notable  manner ;  then  it  de- 
creases again,  as  in  the  male,  as  the  woman  advances  toward  old  age. 

6.  During  the  whole  period  of  pregnancy,  the  exhalation  of  car- 
bonic acid  rises,  for  the  time,  to  the  same  standard  as  in  women 
whose  menses  have  ceased. 

7.  In  both  sexes,  and  at  all  ages,  the  quantity  of  carbonic  acid  is 
greater  as  the  constitution  is  stronger,  and  the  muscular  system 
more  fully  developed.  • 

Prof.  Scharling,  in  a  similar  series  of  investigations,^  found  that 
the  quantity  of  carbonic  acid  exhaled  was  greater  during  the  diges- 
tion of  food  than  in  the  fasting  condition.  It  is  greater,  also,  in  the 
waking  state  than  during  sleep ;  and  in  a  state  of  activity  than  in 
one  of  quietude.  It  is  diminished,  also,  by  fatigue,  and  by  most 
conditions  which  interfere  with  perfect  health. 

The  process  of  respiration  is  not  altogether  confined  to  the  lungs, 
but  the  interchange  of  gases  takes  place,  also,  to  some  extent  through 
the  skin.  It  has  been  found,  by  inclosing  one  of  the  limbs  in  an 
air-tight  case,  that  the  air  in  which  it  is  confined  loses  oxygen  and 
gains  in  carbonic  acid.  By  an  experiment  of  this  sort,  performed  by 
Prof.  Scharling,^  it  was  ascertained  that  the  carbonic  acid  given  off 
from  the  whole  cutaneous  surface,  in  the  human  subject,  is  from 
one-sixtieth  to  one-thirtieth  of  that  discharged  during  the  same 
period  from  the  lungs.  In  the  true  amphibious  animals,  that  is, 
those  which  breathe  by  lungs,  and  can  yet  remain  under  water  for 
an  indefinite  period  without  injury  (as  frogs,  and  salamanders),  the 
respiratory  function  of  the  skin  is  very  active.  In  these  animals, 
the  integument  is  very  vascular,  moist,  and  flexible ;  and  is  covered, 
not  with  dry  cuticle,  but  with  a  very  thin  and  delicate  layer  of 
epithelium.  It,  therefore,  presents  all  the  conditions  necessary  for 
the  accomplishment  of  respiration ;  and  while  the  animal  remains 
beneath  the  surface,  and  the  lungs  are  in  a  state  of  inactivity,  the 
exhalation  and  absorption  of  gases  continue  to  take  place  through 
the  skin,  and  the  process  of  respiration  goes  on  in  a  nearly  unin- 
terrupted, manner. 

*  Annales  de  Chimie  et  de  Pharmacie,  vol.  viii.  p.  490. 

2  lu  Carpenter's  Human  Physiology,  Philada.  ed.,  1855,  p.  308. 


ANIMAL    HEAT.  253 


CHAPTER  XIII. 

ANIMAL    HEAT. 

One  of  the  most  important  phenomena  presented  by  animals  and 
vegetables  is  the  property  whicb  tbey  possess  of  maintaining,  more 
or  less  constantly,  a  standard  temperature,  notwithstanding  the 
external  vicissitudes  of  heat  and  cold  to  which  they  may  be  sub- 
jected. If  a  bar  of  iron,  or  a  jar  of  water,  be  heated  up  to  100°  or 
200°  F.,  and  then  exposed  to  the  air  at  50°  or  60°,  it  will  imme- 
diately begin  to  lose  heat  by  radiation  and  conduction ;  and  this 
loss  of  heat  will  steadily  continue,  until,  after  a  certain  time,  the 
temperature  of  the  heated  body  has  become  reduced  to  that  of  the 
surrounding  atmosphere.  It  then  remains  stationary  at  this  point, 
unless  the  temperature  of  the  atmosphere  should  happen  to  rise  or 
fall :  in  which  case,  a  similar  change  takes  place  in  the  inorganic 
body,  its  temperature  remaining  constant,  or  varying  with  that  of 
the  surrounding  medium. 

With  living  animals  the  case  is  different.  If  a  thermometer  be 
introduced  into  the  stomach  of  a  dog,  or  placed  under  the  tongue 
of  the  human  subject,  it  will  indicate  a  temperature  of  100°  F.,  very 
nearly,  whatever  may  be  the  condition  of  the  surrounding  atmo- 
sphere at  the  time.  This  internal  temperature  is  the  same  in  sum- 
mer and  in  winter.  If  the  individual  upon  whom  the  experiment 
has  been  tried  be  afterward  exposed  to  a  cold  of  zero,  or  even  of  20° 
or  30°  below  zero,  the  thermometer  introduced  into  the  interior  of 
the  body  will  still  stand  at  100°  F.  As  the  body,  during  the  whole 
period  of  its  exposure,  must  have  been  losing  heat  by  radiation  and 
conduction,  like  any  inorganic  mass,  and  has,  notwithstanding,  main- 
tained a  constant  temperature,  it  is  plain  that  a  certain  amount  of 
heat  has  been  generated  in  the  interior  of  the  body  by  means  of  the 
vital  processes,  sufficient  to  compensate  for  the  external  loss.  The 
internal  heat,  so  produced,  is  known  by  the  name  of  vital  or  animal 
heat. 

There  are  two  classes  of  animals  in  which  the  production  of  vital 


254  ANIMAL    HEAT. 

heat  ta,kes  place  with  such  activity  that  their  blood  and  internal 
organs  are  nearly  always  very  much  above  the  external  temper- 
ature; and  which  are  therefore  called  "warm-blooded  animals." 
These  are  mammalia  and  birds.  Among  the  birds,  some  species, 
as  the  gull,  have  a  temperature  as  low  as  100°  F. ;  but  in  most  of 
them,  it  is  higher,  sometimes  reaching  as  high  as  110°  or  111°.  In 
the  mammalians,  to  which  class  man  belongs,  the  animal  tempera- 
ture is  never  far  from  100°.  In  the  seal  and  the  Greenland  whale, 
it  has  been  found  to  be  104° ;  and  in  the  porpoise,  which  is  an  air- 
breathing  animal,  99°.5.  In  the  human  subject  it  is  98°  to  100°. 
When  the  temperature  of  the  air  is  below  this,  the  external  parts 
of  the  body,  being  most  exposed  to  the  cooling  influences  of  radia- 
tion and  conduction,  fall  a  little  below  the  standard,  and  may  indi- 
cate a  temperature  of  97°,  or  even  several  degrees  below  this  point. 
Thus,  on  a  very  cold  day,  the  thinner  and  more  exposed  parts,  such 
as  the  nose,  the  ears,  and  the  ends  of  the  fingers,  may  become 
cooled  down  considerably  below  the  standard  temperature,  and  may 
even  be  congealed,  if  the  cold  be  severe ;  but  the  temperature  of 
the  internal  organs  and  of  the  blood  still  remains  the  same  under 
all  ordinary  exposures. 

If  the  cold  be  so  intense  and  long  continued  as  to  affect  the 
general  temperature  of  the  blood,  it  at  once  becomes  fatal.  It  has 
been  found  that  although  a  warm-blooded  animal  usually  preserves 
its  natural  temperature  when  exposed  to  external  cold,  yet  if  the 
actual  temperature  of  the  blood  become  reduced  by  any  means 
more  than  5°  or  6°  below  its  natural  standard,  death  inevitably 
results.  The  animal,  under  these  circumstances,  gradually  becomes 
torpid  and  insensible,  and  all  the  vital  operations  finally  cease. 
Birds,  accordingly,  whose  natural  temperature  is  about  110°,  die  if 
the  blood  be  cooled  down  to  100°,  which  is  the  natural  temperature 
of  the  mammalia ;  and  the  mammalians  die  if  their  blood  be  cooled 
down  below  94°  or  95°.  Each  of  these  different  classes  has  there- 
fore a  natural  temperature,  at  which  the  blood  must  be  maintained 
in  order  to  sustain  life ;  and  even  the  different  species  of  animals, 
belonging  to  the  same  class,  have  each  a  specific  temperature  which 
is  characteristic  of  them,  and  which  cannot  be  raised  or  lowered,  to 
any  considerable  extent,  without  producing  death. 

While  in  the  birds  and  mammalians,  however,  the  internal  pro- 
duction of  heat  is  so  active,  that  their  temperature  is  nearly  always 
considerably  above  that  of  the  surrounding  media,  and  suffers  but 
little  variation ;  in  reptiles  and  fish,  on  the  other  hand,  its  produc- 


ANIMAL    HEAT. 


255 


tion  is  mucli  less  rapid,  and  the  temperature  of  their  bodies  differs 
but  little  from  that  of  the  air  or  water  which  they  inhabit.  Birds 
and  mammalians  are  therefore  called  "  warm-blooded,"  and  reptiles 
and  fish  "  cold-blooded"  animals.  There  is,  however,  no  other  dis- 
tinction between  them,  in  this  respect,  than  one  of  degree.  In 
reptiles  and  fish  there  is  also  an  internal  source  of  heat ;  only  this 
is  not  so  active  as  in  the  other  classes.  Even  in  these  animals  a 
difference  is  usually  found  to  exist  between  the  temperature  of  their 
bodies  and  that  of  the  surrounding  media.  John  Hunter,  Sir 
Humphrey  Davy,  Czermak,  and  others,'  have  found  the  temperature 
of  Proteus  anguinus  to  be  63°.5,  when  that  of  the  air  was  55°.4:; 
that  of  a  frog  48",  in  water  at  44^.4 ;  that  of  a  serpent  88°.46,  in 
air  at  81°.5 ;  that  of  a  tortoise  84°,  in  air  at  79°.5 ;  and  that  of  fish 
to  be  from  1°.7  to  2°.5  above  that  of  the  surrounding  water. 

The  following  list^  shows  the  mean  temperature  belonging  to 
animals  of  different  classes  and  species. 


Animal. 

Mean  Tempekatpre. 

■  Swallow 1110.25 

Heron    . 

1110.2 

BiBDS. 

Raven   . 

Pigeon  . 

Fowl      . 

.  Gull       . 

Squirrel 
Goat      . 
Cat 

108O.5 

1070.6 

106O.7 

1000.0 

1050 

1020.5      • 

1010.3 

Mammalia.     . 

Hare 
Ox 

Dog       . 
Man 
Ape 

1000.4 
990.5 
990.4 
980.6 
950.9 

Reptile. 

Toad      . 
f  Carp      . 

.      510. 6 
5 10. 25 

Fish. 

Tench  . 

520.10 

In  the  invertebrate  animals,  as  a  general  rule,  the  internal  heat 
is  produced  in  too  small  quantity  to  be  readily  estimated.  In  some 
of  the  more  active  kinds,  however,  such  as  insects  and  arachnida, 
it  is  occasionally  generated  with  such  activity  that  it  may  be 
appreciated  by  the  thermometer.  Thus,  the  temperature  of  the 
butterfly,  when  in  a  state  of  excitement,  is  from  5°  to  9°  above 
that  of  the  air;  and  that  of  the  humble-bee  from  3°  to  10°  higher 


'  Simon's  Chemistry  of  Man,  Philadelphia  edition,  p.  124. 
2  Ibid.,  pp.  123—126. 


256  ANIMAL    HEAT. 

than  the  exterior.  According  to  the  experiments  of  Mr.  Newport/ 
the  interior  of  a  hive  of  bees  may  have  a  temperature  of  48°.5. 
when  the  external  atmosphere  is  at  34°. 5,  even  while  the  insects 
are  quiet ;  but  if  they  be  excited,  by  tapping  on  the  outside  of  the 
hive,  it  may  rise  to  102°.  In  all  cases,  while  the  insect  is  at  rest, 
the  temperature  is  very  moderate ;  but  if  kept  in  rapid  motion  in 
a  confined  space,  it  may  generate  heat  enough  to  aflect  the  thermo- 
meter sensibly,  in  the  course  of  a  few  minutes. 

Even  in  vegetables  a  certain  degree  of  heat-producing  power  is 
occasionally  manifest.  Usually,  the  exposed  surface  of  a  plant  is 
so  extensive  in  proportion  to  its  mass,  that  whatever  caloric  may 
be  generated  is  too  rapidly  lost  by  radiation  and  evaporation,  to  be 
appreciated  by  ordinary  means.  Under  some  circumstances,  how- 
ever, it  may  accumulate  to  such  an  extent  as  to  become  readily 
perceptible.  In  the  process  of  malting,  for  example,  when  a  large 
quantity  of  germinating  grain  is  piled  together  in  a  mass,  its  ele- 
vated temperature  may  be  readily  distinguished,  both  by  the  hand 
and  the  thermometer.  During  the  flowering  process,  also,  an  un- 
usual evolution  of  heat  takes  place  in  plants.  The  flowers  of  the 
geranium  have  been  found  to  have  a  temperature  of  87°,  while 
that  of  the  air  was  81°;  and  the  thermometer,  placed  in  the  centre 
of  a  clump  of  blossoms  of  arum  cordifolium,  has  been  seen  to  rise 
to  111°,  and  even  121°,  while  the  temperature  of  the  external  air 
was  only  Q6°.' 

Dutrochet  has  moreover  found,  by  a  series  of  very  ingenious  and 
delicate  experiment,^  that  nearly  all  parts  of  a  living  plant  gene- 
rate a  certain  amount  of  heat.  The  proper  heat  of  the  plant  is 
usually  so  rapidly  dissipated  by  the  continuous  evaporation  of  its 
fluids,  that  it  is  mostly  imperceptible  by  ordinary  means ;  but  if 
this  evaporation  be  prevented,  by  keeping  the  air  charged  with 
watery  vapor,  the  heat  becomes  sensible  and  can  be  appreciated  by 
a  delicate  thermometer.  Dutrochet  used  for  this  purpose  a  thermo- 
electric apparatus,  so  constructed  that  an  elevation  of  temperature 
of  1°  F.,  in  the  substances  examined,  would  produce  a  deviation  in 
the  needle  of  nearly  nine  degrees.  By  this  means  he  found  that  he 
could  appreciate,  without  difficulty,  the  proper  temperature  of  the 
plant.     A  certain  amount  of  heat  was  constantly  generated,  during 

'  Carpenter's  General  and  Comparative  Physiology,  PliiladelpWa,  1851,  p.  852. 

2  Carpenter's  Gen.  and  Comp.  Physiology,  p.  846. 

3  Annales  des  Sciences  Naturelles,  2d  series,  xii.  p.  277. 


ANIMAL    HEAT.  257 

the  day,  in  tlie  green  stems,  the  leaves,  the  buds,  and  even  the 
roots  and  fruit.  The  maximum  temperature  of  these  parts,  above 
that  of  the  surrounding  atmosphere,  was  sometimes  a  little  over 
one- half  a  degree  Fahrenheit;  though  it  was  often  considerably 
less  than  this. 

The  different  parts  of  the  vegetable  fabric,  therefore,  generate 
different  quantities  of  caloric.  In  the  same  manner,  the  heat- 
producing  power  is  not  equally  active  in  different  species  of  ani- 
mals; but  its  existence  is  nevertheless  common  to  both  animals 
and  vegetables. 

With  regard  to  the  mode  of  generation  of  this  internal  or  vital 
heat,  we  may  start  with  the  assertion  that  its  production  depends 
upon  changes  of  a  chemical  nature,  and  is  so  far  to  be  regarded  as 
a  chemical  phenomenon.  The  sources  of  heat  which  we  meet  with 
in  external  nature  are  of  various  kinds.  Sometimes  the  heat  is  of 
a  physical  origin ;  as,  for  example,  that  derived  from  the  rays  of 
the  sun,  the  friction  of  solid  substances,  or  the  passage  of  electric 
currents.  In  other  instances  it  is  produced  by  chemical  changes : 
and  the  most  abundant  and  useful  source  of  artificial  heat  is  the 
oxidation,  or  combustion,  of  carbon  and  carbonaceous  compounds. 
"Wood  and  coal,  substances  rich  in  carbon,  are  mostly  used  for  this 
purpose ;  and  charcoal,  which  is  nearly  pure  carbon,  is  frequently 
employed  by  itself.  These  substances,  when  burnt,  or  oxidized, 
evolve  a  large  amount  of  heat ;  and  produce,  as  the  result  of  their 
oxidation,  carbonic  acid.  In  order  that  the  process  may  go  on,  it 
is  of  course  necessary  that  oxygen,  or  atmospheric  air,  should  have 
free  access  to  the  burning  body;  otherwise  the  combustion  and 
evolution  of  heat  cease,  for  want  of  a  necessary  agent  in  the  chemi- 
cal combination.  In  all  these  instances,  the  quantity  of  heat  gene- 
rated is  in  direct  proportion  to  the  amount  of  oxidation ;  and  may 
be  measured,  either  by  the  quantity  of  carbon  consumed,  or  by  that 
of  carbonic  acid  produced.  It  may  be  made  to  go  on,  also,  either 
rapidly  or  slowly,  according  to  the  abundance  and  purity  in  which 
oxygen  is  supplied  to  the  carbonaceous  substance.  Thus,  if  char- 
coal be  ignited  in  an  atmosphere  of  pure  oxygen,  it  burns  rapidly 
and  violently,  raises  the  temperature  to  a  high  point,  and  is  soon 
entirely  consumed.  On  the  other  hand,  if  it  be  shut  up  in  a  close 
stove,  to  which  the  air  is  admitted  but  slowly,  it  produces  only  a 
slight  elevation  of  temperature,  and  may  require  a  much  longer 
time  for  its  complete  disappearance.  Nevertheless,  for  the  same 
quantity  of  carbon  consumed,  the  amount  of  heat  generated,  and 
17 


258  ANIMAL    HEAT. 

that  of  carbonic  acid  produced,  will  be  equal  in  the  two  cases.  In 
one  instance  we  have  a  rapid  combustion,  in  the  other  a  slow  com- 
bustion ;  the  total  eflect  being  the  same  in  both. 

Such  is  the  mode  in  which  heat  is  commonly  produced  by  artifi- 
cial means,  its  evolution  is  here  dependent  upon  two  principal 
conditions,  which  are  essential  to  it,  and  by  which  it  is  always 
accompanied,  viz.,  the  consumption  of  oxygen,  and  the  production 
of  carbonic  acid. 

Now,  since  the  two  phenomena  just  mentioned  are  presented 
also  by  the  living  body,  and  since  they  are  accompanied  here,  too, 
by  the  production  of  animal  heat,  it  was  very  natural  to  suppose 
that  in  the  animal  organization,  as  well  as  elsewhere,  the  internal 
heat  must  be  owing  to  an  oxidation  or  combustion  of  carbon.  Ac- 
cording to  Lavoisier,  the  oxygen  taken  into  the  lungs  was  sup- 
posed to  combine  immediately  with  the  carbon  of  the  pulmonary 
tissues  and  fluids,  producing  carbonic  acid,  and  to  be  at  once  re- 
turned under  that  form  to  the  atmosphere ;  the  same  quantity  of 
beat  resulting  from  the  above  process  as  would  have  been  produced 
by  the  oxidation  of  a  similar  quantity  of  carbon  in  wood  or  coal. 
Accordingly,  he  regarded  the  lungs  as  a  sort  of  stove  or  furnace, 
by  which  the  rest  of  the  body  was  warmed,  through  the  medium  of 
the  circulating  blood. 

It  was  soon  found,  however,  that  this  view  was  altogether  erro- 
neous ;  for  the  slightest  exEwnination  shows  that  the  lungs  are  not 
perceptibly  warmer  than  the  rest  of  the  body ;  and  that  the  heat- 
producing  power,  whatever  it  may  be,  does  not  reside  exclusively 
in  the  pulmonary  tissue.  Furthermore,  subsequent  investigations 
showed  the  following  very  important  facts,  which  we  have  already 
mentioned,  viz.,  that  the  carbonic  acid  is  not  formed  in  the  lungs, 
but  exists  in  the  blood  before  its  arrival  in  the  pulmonary  capilla- 
ries ;  and  that  the  oxygen  of  the  inspired  air,  so  far  from  combining 
with  carbon  in  the  lungs,  is  taken  up  in  solution  by  the  blood- 
globules,  and  carried  away  by  the  current  of  the  general  circulation. 
It  is  evident,  therefore,  that  this  oxidation  or  combustion  of  the 
blood  must  take  place,  if  at  all,  not  in  the  lungs,  but  in  the  capil- 
laries of  the  various  organs  and  tissues  of  the  body. 

Liebig  accordingly  adopted  Lavoisier's  theory  of  the  production 
of  animal  heat,  with  the  above  modification.  He  believed  the  heat 
of  the  animal  body  to  be  produced  by  the  oxidation  or  combustion 
of  certain  elements  of  the  food  while  still  circulating  in  the  blood ; 
these  substances  being  converted  into  carbonic  acid  and  water  by 


ANIMAL    HEAT,  259 

tlie  oxidation  of  their  carbon  and  hydrogen,  and  immediately  ex- 
pelled from  the  body  without  ever  having  formed  a  part  of  the  solid 
tissues.  He  therefore  divided  the  food  into  two  different  classes  of 
alimentary  substances ;  viz.,  1st,  the  nitrogenous  or  plastic  elements, 
which  are  introduced  in  comparatively  small  quantity,  and  which 
are  to  be  actually  converted  into  the  substance  of  the  tissues,  such  as 
albumen,  muscular  flesh,  &c. ;  and  2d,  the  hydro-carbons  or  respiratory 
elements,  such  as  sugar,  starch,  and  fat ;  which,  according  to  his  view, 
are  taken  into  the  blood  solely  to  be  burned,  never  being  assimilated 
or  converted  into  the  tissues,  but  only  oxidized  in  the  circulation, 
and  immediately  expelled,  as  above,  under  the  form  of  carbonic 
acid  and  water.  He  therefore  regarded  these  elements  of  the  food 
only  as  so  much  fuel ;  destined  simply  to  maintain  the  heat  of  the 
body,  but  taking  no  part  in  the  proper  function  of  nutrition. 

The  above  theory  of  animal  heat  has  been  very  generally  adopted 
and  acknowledged  by  the  medical  profession  until  within  a  recent 
period.  A  few  years  ago,  however,  some  of  its  deficiencies  and 
inconsistencies  were  pointed  out,  by  Lehmann  in  Germany,  and  by 
Eobin  and  Yerdeil  in  France ;  and  since  that  time  it  has  begun  to 
lose  ground  and  give  place  to  a  different  mode  of  explanation,  more 
in  accordance  with  the  present  state  of  physiological  science.  We 
believe  it,  in  fact,  to  be  altogether  erroneous;  and  incapable  of 
explaining,  in  a  satisfactory  manner,  the  phenomena  of  animal  heat, 
as  exhibited  by  the  living  body.  We  shall  now  proceed  to  pass  in 
review  the  principal  objections  to  the  theory  of  combustion,  con- 
sidered as  a  physiological  doctrine. 

I.  It  is  not  at  all  necessary  to  regard  the  evolution  of  heat  as 
dependent  solely  on  direct  oxidation.  This  is  only  one  of  its 
sources,  as  we  see  constantly  in  external  nature.  The  sun's  rays, 
mechanical  friction,  electric  currents,  and  more  particularly  a  great 
variety  of  chemical  actions,  such  as  various  saline  combinations  and 
decompositions,  are  all  capable  of  producing  heat;  and  even  simple 
solutions,  such  as  the  solution  of  caustic  potassa  in  water,  the  mixture 
of  sulphuric  acid  and  water,  or  of  alcohol  and.  water,  will  often  pro- 
duce a  very  sensible  elevation  of  temperature.  Now  we  know  that 
in  the  interior  of  the  body  a  thousand  different  actions  of  this 
nature  are  constantly  going  on  ;  solutions,  combinations  and  decom- 
positions in  endless  variety,  all  of  which,  taken  together,  are  amply 
sufficient  to  account  for  the  production  of  animal  heat,  provided  the 
theory  of  combustion  should  be  found  insufficient  or  improbable. 


*2G0  ANIMAL    HEAT. 

II.  In  vegetables  there  is  an  internal  production  of  heat,  as  well 
as  in  animals ;  a  fact  which  has  been  fully  demonstrated  by  the 
experiments  of  Dutrochet  and  others,  already  described.  In  vege- 
tables, however,  the  absorption  of  oxygen  and  exhalation  of  car- 
bonic acid  do  not  take  place ;  excepting,  to  some  extent,  during  the 
nio-ht.  On  the  contrary,  the  diurnal  process  in  vegetables,  it  is  well 
known,  is  exactly  the  reverse  of  this.  Under  the  influence  of  the 
solar  light  they  absorb  carbonic  acid  and  exhale  oxygen.  And  it 
is  exceedingly  remarkable  that,  in  Dutrochet's  experiments,  he 
found  that  the  evolution  of  heat  by  plants  was  always  accompanied 
by  the  disappearance  of  carbonic  acid  and  the  exhalation  of  oxygen. 
Plants  which,  in  the  daylight,  exhale  oxygen  and  evolve  heat,  if 
placed  in  the  dark,  immediately  begin  to  absorb  oxygen  and  exhale 
carbonic  acid ;  and,  at  the  same  time,  the  evolution  of  heat  is  sus- 
pended. Dutrochet  even  found  that  the  evolution  of  heat  by  plants 
presented  a  regular  diurnal  variation;  and  that  its  maximum  of 
intensity  was  about  the  middle  of  the  day,  just  at  the  time  when  the 
absorption  of  carbonic  acid  and  the  exhalation  of  oxygen  are  going  on 
with  the  greatest  activity.  The  proper  heat  of  plants,  therefore,  can- 
not be  the  result  of  oxidation  or  combustion,  but  must  be  dependent 
on  an  entirely  different  orocess. 

III.  In  animals,  the  quantities  of  oxygen  absorbed  and  of  carbonic 
acid  exhaled  do  not  correspond  with  each  other.  Most  frequently 
a  certain  amount  of  oxygen  disappears  in  the  body,  over  and  above 
that  which  is  returned  in  the  breath  under  the  form  of  carbonic 
acid.  This  overplus  of  oxygen  has  been  said  to  unite  with  the 
hydrogen  of  the  food,  so  as  to  form  water  which  also  passes  out 
by  the  lungs;  but  this  is  a  pure  assumption,  resting  on  no  direct 
evidence  whatever,  for  we  have  no  experimental  proof  that  any 
more  watery  vapor  is  exhaled  from  the  lungs  than  is  supplied  by 
the  fluids  taken,  into  the  stomach.  It  is  superfluous,  therefore,  to 
assume  that  any  of  it  is  produced  by  the  oxidation  of  hydrogen. 

Furthermore,  the  proportion  of  overplus  oxygen  which  disap- 
pears in  the  body,  beside  that  which  is  exhaled  in  the  carbonic  acid 
of  the  breath,  varies  greatly  in  the  same  animal  according  to  the 
quality  of  the  food.  Eegnault  and  Eeiset"  found  that  in  dogs,  fed 
on  meat,  the  oxygen  which  reappeared  under  the  form  of  carbonic 
acid  was  only  75  per  cent,  of  the  whole  quantity  absorbed ;  while 

'  Annales  de  Chimie  et  cie  Physique,  3d  series,  xxvi.  p.  428. 


ANIMAL    HEAT.  261 

in  dogs  fed  on  vegetable  substances  it  amounted  to  over  90  per 
cent.  In  some  instances,'  where  the  animals  (rabbits  and  fowls) 
were  fed  on  bread  and  grain  exclusively,  the  proportion  of  expired 
oxygen  amounted  to  101  or  even  102  per  cent. ;  that  is,  more  oxygen 
was  actually  cordained  in  the  carbonic  acid  exhaled,  than  had  been  ab- 
sorbed in  a  free  state  from  the  atmosphere.  A  portion,  at  least,  of  the 
carbonic  acid  must  therefore  have  been  produced  by  other  means 
than  direct  oxidation. 

lY.  It  has  already  been  shown,  in  a  previous  chapter,  that  the 
carbonic  acid  which  is  exhaled  from  the  lungs  is  not  primarily 
formed  in  the  blood,  but  makes  its  appearance  in  the  substance  of 
the  tissues  themselves ;  and  furthermore,  that  even  here  it  does  not 
originate  by  a  direct  oxidation,  but  rather  by  a  process  of  decom- 
position, similar  to  that  by  which  sugar,  in  fermentation,  is  resolved 
into  alcohol  and  carbonic  acid.  We  understand  from  this  bow  to 
explain  the  singular  fact  alluded  to  in  the  last  paragraph,  viz.,  the 
abundant  production  of  carbonic  acid,  under  some  circumstances, 
with  a  comparatively  small  supply  of  free  oxygen.  The  statement 
made  by  Liebig,  therefore,  that  starchy  and  oily  matters  taken  with 
the  food  are  immediately  oxidized  in  the  circulation  without  ever 
being  assimilated  by  the  tissues,  is  without  foundation.  It  never, 
in  fact,  rested  on  any  other  ground  than  a  supposed  probability ; 
and  as  we  see  that  carbonic  acid  is  abundantly  produced  in  the 
body  by  other  means,  we  have  no  longer  any  reason  for  assuming, 
without  direct  evidence,  the  existence  of  a  combustive  process  in 
the  blood. 

Y,  The  evolution  of  heat  in  the  animal  body  is  not  general,  as  it 
would  be  if  it  resulted  from  a  combustion  of  the  blood ;  but  local, 
since  it  takes  place  primarily  in  the  substance  of  the  tissues  them- 
selves. Yarious  causes  will  therefore  produce  a  local  elevation  or 
depression  of  temperature,  by  modifying  the  nutritive  changes 
which  take  place  in  the  tissues.  Thus,  in  the  celebrated  experiment 
of  Bernard,  which  we  have  often  verified,  division  of  the  sympa- 
thetic nerve  in  the  middle  of  the  neck  produces  very  soon  a  marked 
elevation  of  temperature  in  the  corresponding  side  of  the  head  and 
face.  Local  inflammations,  also,  increase  very  sensibly  the  tempera- 
ture of  the  part  in  which  they  arc  seated,  while  that  of  the  general 

'  Annales  de  Cliimio  et  de  Physique,  3d  series,  xxvi.  pp.  409—451. 


262  ANIMAL    HEAT. 

mass  of  the  blood  is  not  altered.  Finally  it  has  been  demonstrated 
by  Bernard  that  in  the  natural  state  of  the  system  there  is  a  marked 
difference  in  the  temperature  of  the  different  organs  and  of  the  blood 
returning  from  them,'  The  method  adopted  by  this  experimenter 
was  to  introduce,  in  the  living  animal,  the  bulb  of  a  fine  thermo- 
meter successively  into  the  bloodvessels  entering  and  those  leaving 
the  various  internal  organs.  The  difference  of  temperature  in  these 
two  situations  showed  whether  the  blood  had  lost  or  gained  in  heat 
while  traversing  the  capillaries  of  the  organ.  Bernard  found,  in 
the  first  place,  that  the  blood  in  passing  through  the  lungs,  so  far 
from  increasing,  was  absolutely  diminished  in  temperature;  the 
blood  on  the  left  side  of  the  heart  being  sometimes  a  little  more 
and  sometimes  a  little  less  than  one-third  of  a  degree  Fahr.  lower 
than  on  the  right  side.  This  slight  cooling  of  the  blood  in  the 
lungs  is  owing  simply  to  its  exposure  to  the  air  through  the  pul- 
monary membrane,  and  to  the  vaporization  of  water  which  takes 
place  in  these  organs.  In  the  abdominal  viscera,  on  the  contrary, 
the  blood  is  increased  in  temperature.  It  is  sensibly  warmer  in  the 
portal  vein  than  in  the  aorta ;  and  very  considerably  warmer  in  the 
hepatic  vein  than  in  either  the  portal  or  the  vena  cava.  The  blood 
of  the  hepatic  vein  is  in  fact  warmer  than  that  of  any  other  part 
of  the  body.  The  production  of  heat,  therefore,  according  to  Ber- 
nard's observations,  is  more  active  in  the  liver  than  in  any  other 
portion  of  the  system.  As  the  chemical  processes  of  nutrition  are 
necessarily  different  in  the  different  tissues  and  organs,  it  is  easy  to 
understand  why  a  specific  amount  of  heat  should  be  produced  in 
each  of  them.  A  similar  fact,  it  will  be  recollected,  was  noticed  by 
Dutrochet,  in  regard  to  the  different  parts  of  the  vegetable  organ- 
ization. 

VI.  Animal  heat  has  been  supposed  to  stand  in  a  special  relation 
to  the  production  of  carbonic  acid,  because  in  warm-blooded  animals 
the  respiratory  process  is  more  active  than  in  those  of  a  lower 
temperature ;  and  because,  in  the  same  animal,  an  increase  or  di- 
minution in  the  evolution  of  heat  is  accompanied  by  a  correspond- 
ing increase  or  diminution  in  the  products  of  respiration.  But 
this  is  also  true  of  all  the  other  excretory  products  of  the  body.  An 
elevation  of  temperature  is  accompanied  by  an  increased  activity 
of  all  the  nutritive  processes.     Not  only  carbonic  acid,  but  the 

>  Gazette  Hebdomadaire,  Aug.  29  and  Sept.  26,  1856. 


ANIMAL    HEAT.  263 

ingredients  of  the  urine  and  the  perspiration  are  discharged  in  larger 
quantity  than  usual.  An  increased  supply  of  food  also  is  required, 
as  well  as  a  larger  quantity  of  oxygen;  and  the  digestive  and 
secretory  processes  both  go  on,  at  the  same  time,  with  unusual 
activity. 

Animal  heat,  then,  is  a  phenomenon  which  results  from  tlie 
simultaneous  activity  of  many  different  processes,  taking  place  in 
many  different  organs,  and  dependent,  undoubtedly,  on  different 
chemical  changes  in  each  one.  The  introduction  of  oxygen  and 
the  exhalation  of  carbonic  acid  have  no  direct  connection  with  each 
other,  but  are  only  the  beginning  and  the  end  of  a  long  series  of 
continuous  changes,  in  which  all  the  tissues  of  the  body  successively 
take  a  part.  Their  relation  is  precisely  that  which  exists  between 
the  food  introduced  through  the  stomach,  and  the  urinary  ingre- 
dients eliminated  by  the  kidneys.  The  tissues  require  for  their 
nutrition  a  constant  supply  of  solid  and  liquid  food  which  is  intro- 
duced through  the  stomach,  and  of  oxygen  which  is  introduced 
through  the  lungs.  The  disintegration  and  decomposition  of  the 
tissues  give  rise,  on  the  one  hand,  to  urea,  uric  acid,  &c.,  which  are 
discharged  with  the  urine,  and  on  the  other  hand  to  carbonic  acid, 
which  is  exhaled  from  the  lungs.  But  the  oxygen  is  not  directly 
converted  into  carbonic  acid,  any  more  than  the  food  is  directly 
converted  into  urea  and  the  urates. 

Animal  heat  is  not  to  be  regarded,  therefore,  as  the  result  of  a 
combustive  process.  There  is  no  reason  for  believing  that  the 
greater  part  of  the  food  is  "  burned"  in  the  circulation.  It  is,  on 
the  contrary,  assimilated  by  the  substance  of  the  tissues ;  and  these, 
in  their  subsequent  disintegration,  give  rise  to  several  excretory 
products,  one  of  which  is  carbonic  acid. 

The  numerous  combinations  and  decompositions  which  follow 
each  other  incessantly  during  the  nutritive  process,  result  in  the 
production  of  an  internal  or  vital  heat,  which  is  present  in  both 
animals  and  vegetables,  and  which  varies  in  amount  in  different 
species,  in  the  same  individual  at  different  times,  and  even,  in 
different  parts  and  organs  of  the  same  body. 


264  THE    CIRCULATION. 


CHAPTER    XIV. 

THE  CIRCULATION. 

The  blood  may  be  regarded  as  a  nutritious  fluid,  holding  in 
solution  all  the  ingredients  necessary  for  the  formation  of  the 
tissues.  In  some  animals  and  vegetables,  of  the  lowest  organization, 
such  as  infusoria,  polypes,  algse,  and  the  like,  neither  blood  nor 
circulation  is  required ;  since  all  parts  of  the  body,  having  a  similar 
structure,  absorb  nourishment  equally  from  the  surrounding  media, 
and  carry  on  nearly  or  quite  the  same  chemical  processes  of  growth 
and  assimilation.  In  the  higher  animals  and  vegetables,  however, 
as  well  as  in  the  human  subject,  the  case  is  different.  In  them,  the 
structure  of  the  body  is  compound.  Different  organs,  with  widely 
different  functions,  are  situated  in  different  parts  of  the  frame ;  and 
each  of  these  functions  is  more  or  less  essential  to  the  continued 
existence  of  the  whole.  In  the  intestine,  for  example,  the  process 
of  digestion  takes  place ;  and  the  prepared  ingredients  of  the  food 
are  thence  absorbed  into  the  bloodvessels,  by  which  they  are 
transported  to  distant  tissues  and  organs.  In  the  lungs,  again, 
ihe  blood  absorbs  oxygen  which  is  afterward  to  be  appropriated  by 
the  tissues ;  and  carbonic  acid,  which  was  produced  in  the  tissues, 
is  exhaled  from  the  lungs.  In  the  liver,  the  kidneys,  and  the  skin, 
other  substances  again  are  produced  or  eliminated,  and  these  local 
processes  are  all  of  them  necessary  to  the  preservation  of  the  general 
organization.  The  circulating  fluid  is,  therefore,  in  the  higher 
animals,  a  means  of  transportation,  by  which  the  substances  pro- 
duced in  particular  organs  are  dispersed  throughout  the  body,  or 
by  which  substances  produced  generally  in  the  tissues  are  conveyed 
to  particular  organs,  in  order  to  be  eliminated  and  expelled. 

The  circulatory  apparatus  consists  of  four  different  parts,  viz : 
1st.  The  heart ;  a  hollow,  muscular  organ,  which  receives  the  blood 
at  one  orifice  and  drives  it  out,  in  successive  impulses,  at  another. 
2d.  The  arteries;  a  series  of  branching  tubes,  which  convey  the 
blood  from  the  heart  to  the  different  tissues  and  organs  of  the  body. 


THE    HEART. 


265 


3d.  The  capillaries;  a  network  of  minute  inosculating  tubules, 
which  are  interwoven  with  the  substance  of  the  tissues,  and  which 
bring  the  blood  into  intimate  contact  with  the  cells  and  fibres  of 
which  thej  are  composed ;  and  4th.  The  veins ;  a  set  of  converg- 
ing vessels,  destined  to  collect  the  blood  from  the  capillaries,  and 
return  it  to  the  heart.  In  each  of  these  four  different  parts  of  the 
circulatory  apparatus,  the  movement  of  the  blood  is  peculiar  and 
dependent  on  special  conditions.  It  will  therefore  require  to  be 
studied  in  each  one  of  them  separately. 


THE  HEART. 


The  structure  of  the  heart,  and  of  the  large  vessels  connected 
with  it,  varies  considerably  in  different  classes  of  animals,  owing  to 
the  different  arrangement  of  the  respiratory  organs.  For  the  respi- 
ratory apparatus  being  one  of  the  most  important  in  the  body,  and 
the  one  most  closely  connected 

by  anatomical   relations   with  Fig'  76. 

the  organs  of  circulation,  the 
latter  are  necessarily  modified 
in  structure  to  correspond  with 
the  former.  In  fish,  for  exam- 
ple (Fig.  76),  the  heart  is  an 
organ  consisting  of  two  princi- 
pal cavities ;  an  auricle  (a)  into 
which  the  blood  is  received  from 
the  central  extremity  of  the 
vena  cava,  and  a  ventricle  (5) 
into  which  the  blood  is  driven 
by  the  contraction  of  the  auricle. 
The  ventricle  is  considerably 
larger  and  more  powerful  than 
the  auricle,  and  by  its  contrac- 
tion drives  the  blood  into  the 
main  artery  supplying  the  gills. 
In  the  gills  (cc)  the  blood  is 
arterialized ;  after  which  it  is 
collected  by  the  branchial  veins. 

These  veins  unite  upon  the  median  line  to  form  the  aorta  (d)  by 
which  the  blood  is  finally  distributed  throughout  the  frame.     In 


CiRcrLATioN  OP  Fish.  —  a.    Auricle,    b. 
Ventricle,     cc.  GUIs.    d.  Aorta,     ee.  Vense  cavre. 


266 


THE    CIRCULATlOiSr. 


Fig.  77. 


these  animals  the  respiratory  process  is  not  a  very  active  one ;  but 
the  gills,  which  are  of  small  size,  being  the  only  respiratory  organs, 
all  the  blood  requires  to  pass  through  them  for  purposes  of  aeration. 
The  heart  here  is  a  single  organ,  destined  only  to  drive  the  blood 
from  the  termination  of  the  venous  system  to  the  capillaries  of  the 
gills. 

In  reptiles,  the  heart  is  composed  of  two  auricles,  placed  side  by 
side,  and  one  ventricle.  (Fig.  77.)     The  ven£e  cavae  discharge  their 

blood  into  the  right  auricle  (a), 
whence  it  passes  into  the  ventricle 
(c).  From  the  ventricle,  a  part  of  it 
is  carried  into  the  aorta  and  distri- 
buted throughout  the  body,  while  a 
part  is  sent  to  the  lungs  through  the 
pulmonary  artery.  The  arterialized 
blood,  returning  from  the  lungs  by 
the  pulmonary  vein,  is  discharged 
into  the  left  auricle  (6),  and  thence 
into  the  ventricle  (c),  where  it 
mingles  with  the  venous  blood 
which  has  just  arrived  by  the  venae 
cavse.  In  the  reptile,  therefore,  the 
ventricle  is  a  common  organ  of  pro- 
pulsion, both  for  the  lungs  and  for 
the  general  circulation.  In  these 
animals  the  aeration  of  the  blood  in 
the  lungs  is  only  partial ;  a  certain 
portion  of  the  blood  which  leaves 
the  heart  being  carried  to  these  organs,  just  as  in  the  human  subject 
it  is  only  a  portion  of  the  blood  which  is  carried  to  the  kidney  by 
the  renal  artery.  This  arrangement  is  sufficient  for  the  reptiles, 
because  in  many  of  them,  such  as  serpents  and  turtles,  the  lungs 
are  much  more  extensive  and  efficient,  as  respiratory  organs,  than 
the  gills  of  fish ;  while  in  others,  such  as  frogs  and  water-lizards, 
the  integument  itself,  which  is  moist,  smooth,  and  naked,  takes  an 
important  share  in  the  aeration  of  the  blood. 

In  quadrupeds  and  the  human  species,  however,  the  respi- 
ratory process  is  not  only  exceedingly  active,  but  the  lungs 
are,  at  the  same  time,  the  only  organs  in  which  the  aeration  of 
the  blood  can  be  fully  accomplished.  In  them,  accordingly,  we 
find   the   two    circulations,  general  and  pulmonary,  entirely  dis- 


ClKCCLATION      OF     RePTII,  ES.  —  <T, 

Eight  auricle,  b.  Leftauricle.  e.  Vpntricle 
d.  Lungs,    e.  Aorta.    /.  Vena  cava. 


THE    HEART. 


267 


tinct  from  eacli  other.  (Fig.  78.)  All  the  blood  returning  from 
the  body  by  the  veins  must  pass  through  the  lungs  before  it  is 
again  distributed  through  the 

arterial   system.      We   have  Fig.  78. 

therefore  a  double  circula- 
tion, and  also  a  double  heart ; 
the  two  sides  of  which, 
though  united  externally, 
are  separate  internally.  The 
mammalian  heart  consists  of 
a  right  auricle  and  ventricle 
(a,  b),  receiving  the  blood 
from  the  vena  cava  (i),  and 
driving  it  to  the  lungs ;  and 
a  left  auricle  and  ventricle 
(/,  g)  receiving  the  blood 
from  the  lungs  and  driving 
it  outward  through  the  arte- 
rial system. 

In  the  complete  or  double 
mammalian  heart,  the  differ- 
ent parts  of  the  organ  present 
certain  peculiarities  and  bear 

certain  relations  to  each  other,  which  it  is  necessary  to  understand 
before  we  can  properly  appreciate  its  action  and  movements.  The 
entire  organ  has  a  more  or  less  conical  form,  its  base  being  situated 
on  the  median  line,  directed  upward  and  backward ;  the  whole  being 
suspended  in  the  chest,  and  loosely  fixed  to  the  spinal  column,  by 
the  great  vessels  which  enter  and  leave  it  at  this  point.  The  apex, 
on  the  contrary,  is  directed  downward,  forward,  and  to  the  left,  sur- 
rounded by  the  pericardium  and  the  pericardial  fluid,  but  capable 
of  a  very  free  lateral  and  rotatory  motion.  The  auricles,  which 
have  a  smaller  capacity  and  thinner  walls  than  the  ventricles,  are 
situated  at  the  upper  and  posterior  part  of  the  organ  (Figs.  79  and 
80) ;  while  the  ventricles  occupy  its  anterior  and  lower  portions^ 
The  two  ventricles,  moreover,  are  not  situated  on  the  same  plane, 
but  the  right  ventricle  occupies  a  position  somewhat  in  front  and 
above  that  of  the  left;  so  that  in  an  anterior  view  of  the  heart  the 
greater  portion  of  the  left  ventricle  is  concealed  by  the  right  (Fig. 
79),  and  in  a  posterior  view  the  greater  portion  of  the  right  ven- 
tricle is  concealed  by  the  left  (Fig.  80) ;  while  in  both  positions  the 


Circulation  in  Mammalians.  —  n.  RigW 
auricle.  6.  Eight  ventricle,  c.  Pulmonary  artery 
d.  Lungs,  e.  Pulmonary  vein.  /.  Left  auricle,  g 
Left  ventricle,    h.  Aorta,    i.  Vena  cava. 


268 


THE    CIRCULATION'. 


apex  of  the  heart  is  constituted  altogether  by  the  point  of  the  left 
ventricle. 

Fig.  80. 


Tic  MAX  Heart,  anterior  view. — 
n.  K:i,'ht  ventricle.  6.  Left  ventricle, 
c.  Eight  auricle,  d.  Le!'t  auricle,  e. 
Pulmonary  artery.    /.  Aorta. 


II UMAX  Hrart,  posterior  view.— 
ti.  Kight  ventricle.  6.  Left  ventricle. 
c.    Eight  auricle,     d.  Left  auricle. 


The  different  cavities  of  the  heart  and  of  the  adjacent  blood- 
vessels, though  continuous  with  each  other,  are  partially  separated 
\>y  certain  constrictions.  These  constricted  orifices,  by  which  the 
different  cavities  communicate,  are  known  by  the  names  of  the 


Fig.  81. 


Ekiht  Auricle  and  Ventricle;  Auriculo-ventricnlar  Valves  open,  Arterial  Valves  closed. 

auricular,  auriculo- ventricular,  and  aortic  and  pulmonary  orifices ; 
the  auricular  orifices  being  the  passages  from  the  venae  cavas  and 


THE    HEART.  269 

pulmonary  veins  into  the  right  and  left  auricles ;  the  auriculo- 
ventricular  orifices  leading  from  the  auricles  into  the  ventricles ; 
and  the  aortic  and  pulmonary  orifices  leading  from  the  ventricles 
into  the  aortic  and  pulmonary  arteries  respectively. 

The  auriculo-ventricular,  aortic,  and  pulmonary  orifices  are  fur- 
nished with  valves,  which  allow  the  blood  to  pass  readily  from  the 
auricles  to  the  ventricles,  and  from  the  ventricles  to  the  arteries, 
but  shut  back,  with  the  contractions  of  the  organ,  so  as  to  prevent 
its  return  in  an  opposite  direction.  The  course  of  the  blood 
through  the  heart  is,  therefore,  as  follows.  From  the  vena  cava  it 
passes  into  the  right  auricle ;  and  from  the  right  auricle  into  the 
right  ventricle.  (Fig.  81.)  On  the  contraction  of  the  right  ventricle, 
the  tricuspid  valves  shut  back,  preventing  its  return  into  the  auricle 
(Fig.  82) ;  and  it  is  thus  driven  through  the  pulmonary  artery  to  the 

Fig.  82. 


Eight  AuaiCLE  and  Vestricle;  Auriculo-ventricular  Valves  closed,  Arterial  Valves  open, 

lungs.  Eeturning  from  the  lungs,  it  enters  the  left  auricle,  thence 
passes  into  the  left  ventricle,  from  which  it  is  finally  delivered  into 
the  aorta,  and  distributed  throughout  the  body.  (Fig.  83.)  This 
movement  of  the  blood,  however,  througb  the  cardiac  cavities,  is 
not  a  continuous  and  steady  flow,  but  is  accomplished  by  alternate 
contractions  and  relaxations  of  the  muscular  parietes  of  the  heart 
80  that  with  every  impulse,  successive  portions  of  blood  are  received 
by  the  auricles,  delivered    into  the  ventricles,  and  by  them  dis- 


270 


THE    CIRCULATION. 


charged  into  the  arteries.     Each  one  of  these  successive  actions  is 
called  a  beat,  or  imlsation  of  the  heart. 

Fig.  83. 


CoTTBSE   OF   Blood   through    the  He  art.— 't,  rr.    Vena  cava,  superior  and  inferior. 
h.  Right  ventricle,     c.  Pulmonary  artery,    d.  Pulmonary  vein.     e.  Left  ventricle.    /.  Aorta. 

Each  pulsation  of  the  heart  is  accompanied  by  certain  important 
phenomena,  which  require  to  be  studied  in  detail.  These  are  the 
sounds,  the  movements,  and  the  impulse. 

The  sounds  of  the  heart  are  two  in  number.  They  can  readily  be 
heard  by  applying  the  ear  over  the  cardiac  region,  when  they  are 
found  to  be  quite  different  from  each  other  in  position,  in  tone,  and 
in  duration.  They  are  distinguished  as  the  first  and  second  sounds 
of  the  heart.  The  first  sound  is  heard  with  the  greatest  intensity 
over  the  anterior  surface  of  the  heart,  and  more  particularly  over 
the  fifth  rib  and  the  fifth  intercostal  space.  It  is  long,  dull,  and 
smothered  in  tone,  and  occupies  one-half  the  entire  duration  of  a 
sino-le  beat.  It  corresponds  in  time  with  the  impulse  of  the  heart 
in  the  precordial  region,  and  the  stroke  of  the  large  arteries  in  the 
immediate  vicinity  of  the  chest.  The  second  sound  follows  imme- 
diately upon  the  first.  It  is  heard  most  distinctly  at  the  situation 
of  the  aortic  and  pulmonary  valves,  viz.,  over  the  sternum  at  the 
level  of  the  third  costal  cartilage.  It  is  short,  sharp,  and  distinct 
in  tone,  and  occupies  only  about  one-quarter  of  the  whole  time  of 


THE    HEART.  271 

a  pulsation.  It  is  followed  by  an  equal  interval  of  silence ;  after 
whicli  the  first  sound  again  recurs.  The  whole  time  of  a  cardiac 
pulsation  may  then  be  divided  into  four  quarters,  of  whicli  the  first 
two  are  occupied  by  tlie  first  sound,  the  third  by  the  second  sound, 
and  the  fourth  by  an  interval  of  silence,  as  follows : — 

fist  quarter  I  p.^^^^^^^^_ 

I   2d        «       ) 
Time  of  pulsation.  -!   o  i         n         o         i  a 

•^  dd         "  Second  sound. 

I   4th        "  Interval  of  silence. 

The  cause  of  the  second  sound  is  universally  acknowledged  to  be 
the  sudden  closure  and  tension  of  the  aortic  and  pulmonary  valves. 
This  fact  is  established  by  the  following  proofs :  1st,  this  sound  is 
heard  with  perfect  distinctness,  as  we  have  already  mentioned,' 
directly  over  the  situation  of  the  above-mentioned  valves ;  2d,  the 
farther  we  recede  in  any  direction  from  this  point,  the  fainter  be- 
comes the  sound ;  and  3d,  in  experiments  upon  the  living  animal, 
often  repeated  by  different  observers,  it  has  been  found  that  if  a 
curved  needle  be  introduced  into  the  base  of  the  large  vessels,  so 
as  to  hook  back  the  semilunar  valves,  the  second  sound  at  once  dis- 
appears, and  remains  absent  until  the  valve  is  again  liberated.  These 
valves  consist  of  fibrous  sheets,  covered  with  a  layer  of  endocardial 
epithelium.  They  have  the  form  of  semilunar  festoons,  the  free 
edge  of  which  is  directed  away  from  the  cavity  of  the  ventricle, 
while  the  attached  edge  is  fastened  to  the  inner  surface  of  the  base 
of  the  artery.  "While  the  blood  is  passing  from  the  ventricle  to  the 
artery,  these  valves  are  thrown  forward  and  relaxed ;  but  when  the 
artery  reacts  upon  its  contents  they  shut  back,  and  their  fibres,  be- 
coming suddenly  tense,  yield  a  clear,  characteristic,  snapping  sound. 

The  production  of  the  first  sound  has  been  attributed  by  some 
writers  to  a  combination  of  various  causes ;  such  as  the  rush  of 
blood  through  the  cardiac  orifices,  the  muscular  contraction  of  the 
parietes  of  the  heart,  the  tension  of  the  auriculo-ventricular  valves, 
the  collision  of  the  particles  of  blood  with  each  other  and  with  the 
surface  of  the  ventricle,  &c.  &c.  We  believe,  however,  with  Andry^ 
and  some  others,  that  the  first  sound  of  the  heart  has  a  similar 
origin  with  the  second;  and  that  it  is  dependent  altogether  on  the 
closure  of  the  auriculo-ventricular  valves.  The  reasons  for  this  con- 
clusion are  the  following : — 

1st.  The  second  sound  is  undoubtedly  caused  by  the  closure  of 

'  Diseases  of  fiie  Heart,  Kneelavid's  translation,  Boston.  1846 


272  THE    CIRCULATION". 

the  semilunar  valves,  and  in  the  action  of  the  heart  the  shutting 
back  of  the  two  sets  of  valves  alternate  with  each  other  precisely 
as  do  the  first  and  second  sounds ;  and  there  is  every  probability, 
to  say  the  least,  that  the  sudden  tension  of  the  valvular  fibres  pro- 
duces a  similar  effect  in  each  instance. 

2d.  The  first  sound  is  heard  most  distinctly  over  the  anterior 
surface  of  the  ventricles,  where  the  tendinous  cords  supporting  the 
auriculo- ventricular  valves  are  inserted,  and  where  the  sound  pro- 
duced by  the  tension  of  these  valves  would  be  most  readily  con- 
ducted to  the  ear. 

3d.  There  is  no  reason  to  believe  that  the  current  of  blood 
through  the  cardiac  orifices  could  give  rise  to  an  appreciable  sound, 
so  long  as  these  orifices,  and  the  cavities  to  which  they  lead,  have 
their  normal  dimensions.  An  unnatural  souffle  may  indeed  origi- 
nate from  this  cause  when  the  orifices  of  the  heart  are  diminished 
in  size,  as  by  calcareous  or  fibrinous  deposits;  and  it  may  also 
occur  in  cases  of  aneurism.  A  souffle  may  even  be  produced  at 
will  in  any  one  of  the  large  arteries  by  pressing  firmly  upon  it 
with  the  end  of  a  stethoscope,  so  as  to  diminish  its  calibre.  But  in 
all  these  instances,  the  abnormal  sound  occurs  only  in  consequence 
of  a  disturbance  in  the  natural  relation  existing  between  the  volume 
of  the  blood  and  the  size  of  the  orifice  through  which  it  passes. 
In  the  healthy  heart,  the  different  orifices  of  the  organ  are  in  exact 
proportion  to  the  quantity  of  the  circulating  blood ;  and  there  is  no 
more  reason  for  believing  that  its  passage  should  give  rise  to  a 
sound  in  the  cardiac  cavities  than  in  the  larger  arteries  or  veins. 

4:th.  The  difference  in  character  between  the  two  sounds  of  the 
heart  depends,  in  all  probability,  on  the  different  arrangement  of 
the  two  sets  of  Valves.  The  second  sound  is  short,  sharp,  and  dis- 
tinct, because  the  semilunar  valves  are  short  and  narrow,  superficial 
in  their  situation,  and  supported  by  the  highly  elastic,  dense  and 
fibrous  bases  of  the  aortic  and  pulmonary  arteries.  The  first  sound 
is  dull  and  prolonged,  because  the  auriculo- ventricular  valves  are 
broad  and  deep-seated,  and  are  attached,  by  their  long  chordae 
tendineae  to  the  comparatively  soft  and  yielding  fleshy  columns  of 
the  heart.  The  difference  between  the  first  and  second  sounds  can, 
in  fact,  be  easily  imitated,  by  simply  snapping  between  the  fingers 
two  pieces  of  tape  or  ribbon,  of  the  same  texture  but  of  different 
lengths.  (Fig.  84.)  The  short  one  will  give  out  a  distinct  and  sharp 
sound ;  the  long  one  a  comparatively  dull  and  prolonged  sound. 

Together  with  the  first  sound  of  the  heart  there  is  also  to  be 


THE    HEART.  273 

heard  a  slight  friction  sound,  produced  by  tlie  collision  of  the  point 
of  the  heart  against  the  parietes  of  the  chest.  This  sound,  which  is 
heard  in  the  fifth  intercostal  space,  is  very  faint,  and  is  more  or  less 

Fig.  84. 


masked  by  the  strong  valvular  sound  which  occurs  at  the  same 
time.  It  is  different,  however,  in  character  from  the  latter,  and 
may  usually  be  distinguished  from  it  by  careful  examination. 

The  movements  of  the  heart  during  the  time  of  a  pulsation  are 
of  a  peculiar  character,  and  have  been  very  often  erroneously 
described.  In  fact  altogether  the  best,  description  of  the  move- 
ments of  the  heart  which  has  yet  appeared,  is  that  given  by  Wil- 
liam Harvey,  in  his  celebrated  work  on  the  Motion  of  the  Seart  and 
Blood,  published  in  1628.  He  examined  the  motion  of  the  heart 
by  opening  the  chest  of  the  living  animal ;  and  though  the  same  or 
similar  experiments  have  been  frequently  performed  since  his  time, 
the  descriptions  given  by  subsequent  observers  have  been  for  the 
most  part  singularly  inferior  to  his,  both  in  clearness  and  fidelity. 
The  method  which  we  have  adopted  for  examining  the  motions  of 
the  heart  in  the  dog  is  as  follows :  The  animal  is  first  rendered 
insensible  by  ether,  or  by  the  inoculation  of  woorara.  The  latter 
mode  is  preferable,  since  a  long-continued  etherization  seems  to 
exert  a  sensibly  depressing  effect  on  the  heart's  action,  which  is 
not  the  case  with  woorara.  The  trachea  is  then  exposed  and 
opened  just  below  the  larynx,  and  the  nozzle  of  a  bellows  inserted 
and  secured  by  ligature.  Finally,  the  chest  is  opened  on  the  me- 
dian line,  its  two  sides  widely  separated,  so  as  to  expose  the  heart 
and  lungs,  the  pericardium  slit  up  and  carefully  cut  away  from  its 
attachments,  and  the  lungs  inflated  by  insufflation  through  the 
trachea.  By  keeping  up  a  steady  artificial  respiration,  the  move- 
18 


274  THE    CIRCULATION". 

ments  of  the  heart  may  be  made  to  continue,  in  favorable  cases,  for 
more  than  an  hour ;  and  its  actions  may  be  studied  by  direct  obser- 
vation, like  those  of  any  external  organ. 

The  examination,  however,  requires  to  be  conducted  with  certain 
precautions,  which  are  indispensable  to  success.  When  the  heart 
is  first  exposed,  its  movements  are  so  complicated,  and  recur  with 
such  rapidity,  that  it  is  difi&cult  to  distinguish  them  perfectly  from 
each  other,  and  to  avoid  a  certain  degree  of  confusion.  Singular 
as  it  may  seem,  it  is  even  difficult  at  first  to  determine  what  period 
in  the  heart's  pulsation  corresponds  to  contraction,  and  what  to 
relaxation  of  the  organ.  We  have  even  seen  several  medical  men, 
watching  together  the  pulsations  of  the  same  heart,  unable  to  agree 
upon  this  point.  It  is  very  evident,  indeed,  that  several  English 
and  continental  observers  have  mistaken,  in  their  examinations,  the 
contraction  for  the  relaxation,  and  the  relaxation  for  the  contrac- 
tion. The  first  point,  therefore,  which  it  is  necessary  to  decide,  in 
examining  the  successive  movements  of  a  cardiac  pulsation,  is  the 
following,  viz :  Which  is  the  contraction  and  which  the  relaxation  of 
the  ventricles  ?  The  method  which  we  have  adopted  is  to  pass  a 
small  silver  canula  directly  through  the  parietes  of  the  left  ven- 
tricle into  its  cavity.  The  blood  is  then  driven  from  the  external 
orifice  of  the  canula  in  interrupted  jets ;  each  jet  indicating  the 
time  at  which  the  ventricle  contracts  upon  its  contents.  The 
canula  is  then  withdrawn,  and  the  different  muscular  layers  of  the 
ventricular  walls,  crossing  each  other  obliquely,  close  the  opening, 
so  that  there  is  little  or  no  subsequent  hemorrhage. 

When  the  successive  actions  of  contraction  and  relaxation  have 
by  this  means  been  fairly  recognized  and  distinguished  from  each 
other,  the  cardiac  pulsations  are  seen  to  be  characterized  by  the 
following  phenomena.  The  changes  in  form  and  position  of  the 
entire  heart  are  mainly  dependent  on  those  of  the  ventricles,  which 
contract  simultaneously  with  each  other,  and  which  constitute  much 
the  largest  portion  of  the  entire  mass  of  the  organ. 

1.  At  the  time  of  its  contraction  the  heart  hardens.  This  pheno- 
menon is  exceedingly  well  marked,  and  is  easily  appreciated  by 
placing  the  finger  upon  the  ventricles,  or  by  grasping  them  between 
the  finger  and  thumb.  The  muscular  fibres  become  swollen  and 
indurated,  and,  if  grasped  by  the  hand,  communicate  the  sensation 
of  a  somewhat  sudden  and  powerful  shock.  It  is  this  forcible  indu- 
ration of  the  heart,  at  the  time  of  contraction,  which  has  been  mis- 
taken by  some  writers  for  an  active  dilatation,  and  described  as 


TUE    HEART.  275 

such.  It  is,  however,  a  phenomenon  precisely  similar  to  that  which 
takes  place  in  the  contraction  of  a  voluntary  muscle,  which  becomes 
swollen  and  indurated  at  the  same  moment  and  in  the  same  propor- 
tion that  it  diminishes  in  length. 

2.  At  the  time  of  contraction,  the  ventricles  elongate  and  the 
point  of  the  heart  protrudes.  This  phenomenon  was  very  well 
described  by  Dr.  Harvey."  "The  heart,"  he  says,  "is  erected,  and 
rises  upward  to  a  point,  so  that  at  this  time  it  strikes  against  the 
breast  and  the  pulse  is  felt  externally."  The  elongation  of  the 
ventricles  during  contraction  has,  however,  been  frequently  denied 
by  subsequent  writers.  The  only  modern  observers,  so  far  as  we 
are  aware,  who  have  recognized  its  existence,  are  Drs.  C.  W.  Pen- 
nock  and  Edward  M.  Moore,  who  performed  a  series  of  very  careful 
and  interesting  experiments  on  the  action  of  the  heart,  in  Philadel- 
phia, in  the  year  1839.^  These  experimenters  operated  upon  calves, 
sheep,  and  horses,  by  stunning  the  animal  with  a  blow  upon  the 
head,  opening  the  chest,  and  keeping  up  artificial  respiration.  They 
observed  an  elongation  of  the  ventricle  at  the  time  of  contraction, 
and  were  even  able  to  measure  its  extent  by  applying  a  shoemaker's 
rule  to  the  heart  while  in  active  motion.  We  are  able  to  corroborate 
entirely  the  statement  of  these  observers  by  the  result  of  our  own 
experiments  on  dogs,  rabbits,  frogs,  &c.  The  ventricular  contrac- 
tion is  an  active  movement,  the  relaxation  entirely  a  passive  one. 
When  contraction  occurs  and  a  stream  of  blood  is  thrown  out  of 
the  ventricle,  its  sides  approximate  each  other  and  its  point  elon- 
gates ;  so  that  the  transverse  diameter  of  the  heart  is  diminished, 
and  its  longitudinal  diameter  increased.  This  can  be  readily  felt 
by  grasping  the  base  of  the  heart  and  the  origin  of  the  large  vessels 
gently  between  the  first  and  middle  fingers,  and  allowing  the  end 
of  the  thumb  of  the  same  hand  to  rest  lightly  upon  its  apex. 
With  every  contraction  the  thumb  is  sensibly  lifted  and  separated 
from  the  fingers,  by  a  somewhat  forcible  elevation  of  the  point  of 
the  heart. 

The  same  thing  can  be  seen,  and  even  measured  by  the  eye, 
in  the  following  manner :  If  the  heart  of  the  frog  or  even  of  any 
small  warm-blooded  animal,  as  the  rabbit,  be  rapidly  removed  from 
the  chest,  it  will  continue  to  beat  for  some  minutes  afterward ;  and 
when  the  rhythmical  pulsations  have  finally  ceased,  contractions 

'  Works  of  William  Harvey,  M.  P.     Sydenham  ed.,  London,  1847,  p.  21. 
*  Philadeljihia  Medical  Examiner,  No.  44. 


276 


THE    CIRCULATION. 


can  still  be  readily  excited  by  touching  the  heart  with  the  point  of 
a  steel  needle.  If  the  heart  be  now  held  by  its  base  between  the 
thumb  and  finger,  with  its  point  directed  upward,  it  will  be  seen 
to  have  a  pyramidal  or  conical  form,  representing  very  nearly  in 
its  outline  an  equilateral  triangle  (Fig.  85) ;  its  base,  while  in  a 
condition  of  rest,  bulging  out  laterally,  while  the  apex  is  compara- 
tively obtuse. 


Fig.  85. 


Fig.  86. 


H K  A  u T  OF  Frog 
in  a  state  of  relaxa- 
tioa. 


Heart    of    F  p.  oo  in  contraction. 


AYhen  the  heart,  held  in  this  position,  is  touched  with  the  point 
of  a  needle  (Fig.  86),  it  starts  up,  becomes  instantly  narrower  and 
longer,  its  sides  approximating  and  its  point  rising  to  an  acute 
angle.  This  contraction  is  immediately  followed  by  a  relaxation ; 
the  point  of  the  heart  sinks  down,  and  its  sides  again  bulge  out- 
ward. 

Let  us  now  see  in  what  manner  this  change  in  the  figure  of  the 
ventricles  during  contraction  is  produced.     If  the  muscular  fibres 

of  the  heart  were  arranged  in  the  form  of 
simple  loops,  running  parallel  with  the 
axis  of  the  organ,  the  contraction  of  these 
fibres  would  merely  have  the  effect  of  di- 
minishing the  size  of  the  heart  in  every 
direction.  This  effect  cau  be  seen  in  the 
accompanying  hypothetical  diagram  (Fig. 
87),  where  the  white  outline  represents 
such  simple  looped  fibres  in  a  state  of  re- 
laxation, and  the  dotted  internal  line  indi- 
cates the  form  which  they  would  take  in 
contraction.  In  point  of  fact,  however, 
none  of  the  muscular  fibres  of  the  heart 
run  parallel  to  its  longitudinal  axis.  They  are  disposed,  on  the 
contrary,  in  a  direction  partly  spiral  and  partly  circular.  The  most 
superficial  fibres  start  from  the  base  of  the  ventricles,  and  pass 


Diagram  of  Simple  Looped 
Fibres,  iaielaxation  and  con- 
traction. 


THE    HEART. 


277 


toward  the  apex,  curling  round  the  heart  in  such  a  manner  as  to 
pass  over  its  anterior  surface  in  an  obliquely  spiral  direction,  from 
above  downward,  and  from  right  to  left.  (Fig.  88.)     They  converge 

toward  the  point  of  the  heart,  curl- 
ing round  the  centre  of  its  apex,  and 
then,  changing  their  direction,  be- 
come deep-seated,  run  upward  along 

Fig.  89. 


Fig.  88. 


BuLiiOCK '  s  H  K  AKT,  anterior  view, 
showing  the  superficial  muscularfibres. 


Left  Ventricle  of 
Bullock's  Heart,  show- 
ing the  deep  fibres. 


the  septum  and  internal  surface  of  the  ventricles,  and  terminate 
in  the  columnse  carneae,  and  in  the  inner  border  of  the  auriculov 
ventricular  ring.  The  deepest  layers  of  fibres,  on  the  contrary,  are 
wrapped  round  the  ventricles  in  a  nearly  circular  direction  (Fig. 
89);  their  points  of  origin  and  attachment  being  still  the  auriculo- 
ventricular  ring,  and  the  points  of  the  fleshy  columns.  The  entire 
arrangement  of  the  muscular  bundles  may  be  readily  seen  in  a 
heart  which  has  been  boiled  for  six  or  eight  hours,  so  as  to  soften 
the  connecting  areolar  tissue,  and  enable  the  fibrous  layers  to  be 
easily  separated  from  each  other. 

By  far  the  greater  part  of  the  mass  of  the  fibres  have  therefore 
a  circular  instead  of  a  longitudinal  direction.  When  they  contract, 
their  action  tends  to  draw  the  lateral  walls  of  the  ventricles  together, 
and  thus  to  diminish  the  transverse  diameter  of  the  heart ;  but  as 
each  muscular  fibre  becomes  thickened  in  direct  proportion  to  its 
contraction,  their  combined  lateral  swelling  necessarily  pushes  out 
the  apex  of  the  ventricle,  and  the  heart  elongates  at  the  same  time 
that  its  sides  are  drawn  together.  This  effect  is  illustrated  in  the 
accompanying  diagram  (Fig.  90),  where  the  white  lines  show  the 
figure  of  the  heart  during  relaxation,  with  the  course  of  its  circular 


278 


THE    CIRCULATION". 


Fiir.  90. 


fibres,  while  the  dotted   line  shows  the  narrowed  and  elongated 
•fio-ure  necessarily  produced  by  their  contraction.   This  phenomenon, 

therefore,  of  the  protrusion  of  the  apex 
of  the  heart  at  the  time  of  contraction,  is 
not  only  fully  established  by  observation, 
but  is  readily  explained  by  the  anatomical 
structure  of  the  organ. 

3.  Simultaneously  with  the  hardening 
and  elongation  of  the  heart,  its  apex  moves 
slightly  from  left  to  right,  and  rotates  also 
upon  its  own  axis  in  the  same  direction. 
Both  these  movements  result  from  the 
peculiar  spiral  arrangement  of  the  cardiac 
fibres.     If  we  refer  again  to  the  preceding 

Diagram  of  Circular  Fibres     diagrams,  WC  shall    SCC  that,  prOVidcd   the 
OF  THE   Heaut,  aud   their  con-  n     •         •         i      i  -i      t 

traction.  fibres  were  arranged  m  simple  longitudi- 

nal loops  (Fig.  87),  their  contraction  would 
merely  have  the  effect  of  drawing  the  point  of  the  heart  directly 
upward  in  a  straight  line  toward  its  base.  On  the  other  hand,  if 
they  were  arranged  altogether  in  a  circular  direction  (Fig.  90), 
the  apex  would  be  simply  protruded,  also  in  a  direct  line, 
without  deviating  or  twisting  either  to  the 
right  or  to  the  left.  But  in  point  of  fact, 
the  superficial  fibres,  as  we  have  already 
described,  run  spirally,  and,  curling  round 
the  point  of  the  heart,  turn  inward  toward 
its  base ;  so  that  if  the  apex  of  the  organ  be 
viewed  externally,  it  will  be  seen  that  the 
superficial  fibres  converge  toward  its  cen- 
tral point  in  curved  lines,  as  in  Fig.  91.  It 
is  well  known  that  every  curved  muscular 
fibre,  at  the  time  of  its  shortening,  necessa- 
rily approximates  more  or  less  to  a  straight 
line.  Its  curvature  is  diminished  in  exact  proportion  to  the  extent 
of  its  contraction ;  and  if  arranged  in  a  spiral  form,  its  contraction 
tends  in  the  same  degree  to  untwist  the  spiral.  During  the  con- 
traction of  the  heart,  therefore,  its  apex  rotates  on  its  own  axis  in 
the  direction  indicated  by  the  arrows  in  Fig.  91,  viz.,  from  left  to 
right  anteriorly,  and  from  right  to  left  posteriorly.  This  produces 
a  twisting  movement  of  the  apex  in  the  above  direction,  which  is 


Fig   91. 


Converging  Fibres  at 
THE  Apex  op  the  Heakt. 


TTTE    HEAKT.  279 

very  perceptible  to  the  eye  at  each  pulsation  of  the  heart,  when 
exposed  in  the  living  animal. 

4.  The  protrusion  of  the  point  of  the  heart  at  the  time  of  con- 
traction, together  with  its  rotation  upon  its  axis  from  left  to  right, 
brings  the  apex  of  the  organ  in  contact  with  the  parietes  of  the 
chest,  and  produces  the  shock  or  impulse  of  the  heart,  which  is 
readily  perceptible  externally,  both  to  the  eye  and  to  the  touch.' 
In  the  human  subject,  when  in  an  erect  position,  the  heart  strikes 
the  chest  in  the  fifth  intercostal  space,  midway  between  the  edge 
of  the  sternum  and  a  line  drawn  perpendicularly  through  the  left 
nipple.  In  a  supine  position  of  the  body,  the  heart  falls  away  from 
the  anterior  parietes  of  the  chest  so  much  that  the  impulse  may 
disappear  for  the  time  altogether.  This  alternate  recession  and 
advance  of  the  point  of  the  heart,  in  relaxation  and  contraction, 
is  provided  for  by  the  anatomical  arrangement  of  the  pericardium, 
and  the  existence  of  the  pericardial  fluid.  As  the  heart  plays  back- 
ward and  forward,  the  pericardial  fluid  constantly  follows  its 
movements,  receding  as  the  heart  advances,  and  advancing  as  the 
heart  recedes.  It  fulfils,  in  this  respect,  the  same  purpose  as  the 
synovial  fluid,  and  the  folds  of  adipose  tissue  in  the  cavity  of  the 
large  articulations ;  and  allows  the  cardiac  movements  to  take  place 
to  their  full  extent  without  disturbing  or  injuring  in  any  way  the 
adjacent  organs. 

5.  The  rhythm  of  the  heart's  pulsations  is  peculiar  and  somewhat 
complicated.  Each  pulsation  is  made  up  of  a  double  series  of  con- 
tractions and  relaxations.  The  two  auricles  contract  together,  and 
afterward  the  two  ventricles ;  and  in  each  case  the  contraction  is 
immediately  followed  by  a  relaxation.  The  auricular  contraction 
is  short  and  feeble,  and  occupies  the  first  part  of  the  time  of  a 
pulsation.  The  ventricular  contraction  is  longer  and  more  powerful, 
and  occupies  the  latter  part  of  the  same  period.  Following  the 
ventricular  contraction  there  comes  a  short  interval  of  repose,  after 
which  the  auricular  contraction  agains  recurs.  The  auricular  and 
ventricular  contractions,  however,  do  not  alternate  so  distinctly 
with  each  other  (like  the  strokes  of  the  two  pistons  of  a  fire  engine) 
as  we  should  be  led  to  believe  from  the  accounts  which  have  been 
given  by  some  observers.  On  the  contrary,  they  are  connected  and 
continuous.  The  contraction,  which  commences  at  the  auricle,  is 
immediately  propagated  to  the  ventricle,  and  runs  rapidly  from  the 
base  of  the  heart  to  its  apex,  very  much  in  the  manner  of  a  peri- 
staltic motion,  except  that  it  is  more  sudden  and  vigorous. 


280  THE    CIECULATION. 

William  Harvey,  again,  gives  a  better  account  of  this  part  of  the 
heart's  action  than  has  been  published  by  any  subsequent  writer. 
The  following  exceedingly  graphic  and  appropriate  description, 
taken  from  his  book,  shows  that  he  derived  his  knowledge,  not 
from  any  secondary  or  hypothetical  sources,  but  from  direct  and 
careful  study  of  the  phenomena  in  the  living  animal. 

"First  of  all,"  he  says,'  "the  auricle  contracts,  and  in  the  course 
of  its  contraction  throws  the  blood  (which  it  contains  in  ample 
quantity  as  the  head  of  the  veins,  the  storehouse  and  cistern  of  the 
blood)  into  the  ventricle,  which  being  filled,  the  heart  raises  itself 
straightway,  makes  all  its  fibres  tense,  contracts  the  ventricles,  and 
performs  a  beat,  by  which  beat  it  immediately  sends  the  blood 
supplied  to  it  by  the  auricle,  into  the  arteries ;  the  right  ventricle 
sending  its  charge  into  the  lungs  by  the  vessel  which  is  called  vena 
arteriosa,  but  which,  in  structure  and  function,  and  all  things  else, 
is 'an  artery;  the  left  ventricle  sending  its  charge  into  the  aorta, 
and  through  this  by  the  arteries  to  the  body  at  large. 

"  These  two  motions,  one  of  the  ventricles,  another  of  the  auricles, 
take  place  consecutively,  but  in  such  a  manner  that  there  is  a  kind 
of  harmony  or  rhythm  preserved  between  them,  the  two  concurring 
in  such  wise  that  but  one  motion  is  apparent,  especially  in  the 
warmer  blooded  animals,  in  which  the  movements  in  question  are 
rapid.  Nor  is  this  for  any  other  reason  than  it  is  in  a  piece  of 
machinery,  in  which,  though  one  wheel  gives  motion  to  another, 
yet  all  the  wheels  seem  tQ  move  simultaneously;  or  in  that 
mechanical  contrivance  which  is  adapted  to  fire-arms,  where  the 
trigger  being  touched,  down  comes  the  flint,  strikes  against  the 
steel,  elicits  a  spark,  which  falling  among  the  powder,  it  is  ignited, 
upon  which  the  flame  extends,  enters  the  barrel,  causes  the  explo- 
sion, propels  the  ball,  and  the  mark  is  attained ;  all  of  which  inci- 
dents, by  reason  of  the  celerity  with  which  they  happen,  seem  to 
take  place  in  the  twinkling  of  an  eye." 

The  above  description  indicates  precisely  the  manner  in  which 
the  contraction  of  the  ventricle  follows  successively  and  yet  con- 
tinuously upon  that  of  the  auricle.  The  entire  action  of  the  auricles 
and  ventricles  during  a  pulsation  is  accordingly  as  follows :  The 
contraction  begins,  as  we  have  already  stated,  at  the  auricle. 
Thence  it  runs  immediately  forward  to  the  apex  of  the  heart.  The 
entire  ventricle  contracts  vigorously,  its  walls  harden,  its  apex 

'  Op.  cit,  p.  31. 


THE    ARTERIES    AND    THE    ARTERIAL    CIRCULATION.      281 

protrudes,  strikes  against  the  walls  of  the  chest,  and  twists  from 
left  to  right,  the  auriculo-ventricular  valves  shut  back,  the  first 
sound  is  produced,  and  the  blood  is  driven  into  the  aorta  and 
pulmonary  artery.  These  phenomena  occupy  about  one-half  the 
time  of  an  entire  pulsation.  Then  the  ventricle  is  immediately 
relaxed,  and  a  short  period  of  repose  ensues.  During  this  period 
the  blood  flows  in  a  steady  stream  from  the  large  veins  into  the 
auricle,  and  through  the  auriculo-ventricular  orifice  into  the  ven- 
tricle ;  filling  the  ventricle,  by  a  kind  of  passive  dilatation,  about 
two-thirds  or  three-quarters  full.  Then  the  auricle  contracts  with  a 
quick  sharp  motion,  forces  the  last  drop  of  blood  into  the  ventricle, 
distending  it  to  its  full  capacity,  and  then  the  ventricular  contraction 
follows,  as  above  described,  driving  the  blood  into  the  large  arteries. 
These  movements  of  contraction  and  relaxation  continue  to  alter- 
nate with  each  other,  and  form,  by  their  recurrence,  the  successive 
cardiac  pulsations. 

THE   ARTERIES  AND  THE   ARTERIAL   CIRCULATION. 

The  arteries  are  a  series  of  branching  tubes  which  commence 
with  the  aorta  and  ramify  throughout  the  body,  distributing  the 
blood  to  all  the  vascular  organs.  They  are  composed  of  three 
coats,  viz:  an  internal  homogeneous  tunic,  continuous  with  the 
endocardium ;  a  middle  coat,  composed  of  elastic  and  muscular 
fibres ;  and  an  external  or  "  cellular"  coat,  composed  of  condensed 
layers  of  areolar  tissue.  The  essential  anatomical  difference  be- 
tween the  larger  and  the  smaller  arteries  consists  in  the  structure 
of  their  middle  coat.  In  the  smaller  arteries  this  coat  is  composed 
exclusively  of  smooth  muscular  fibres,  arranged  in  a  circular  man- 
ner around  the  vessel,  like  the  circular  fibres  of  the  muscular  coat 
of  the  intestine.  In  arteries  of  medium  size  the  middle  coat  con- 
tains both  muscular  and  elastic  fibres ;  while  in  those  of  the  largest 
calibre  it  consists  of  elastic  tissue  alone.  The  large  arteries,  ac- 
cordingly, possess  a  remarkable  degree  of  elasticity  and  little  or  no 
contractility ;  while  the  smaller  are  contractile,  and  but  little  or  not 
at  all  elastic. 

It  is  found,  by  measuring  the  diameters  of  the  successive  arte- 
rial ramifications,  that  the  combined  area  of  all  the  branches  given 
off  from  a  trunk  is  somewhat  greater  than  that  of  the  original 
vessel ;  and  therefore  that  the  combined  area  of  all  the  small  arte- 
ries must  be  considerably  larger  than  that  of  the  aorta,  from  which 


282  THE    CIRCULATION. 

the  arterial  system  originates.  As  the  blood,  consequently,  in  its 
passage  from  the  heart  outward,  flows  successively  through  larger 
and  larger  spaces,  the  rapidity  of  its  circulation  must  necessarily 
be  diminished,  in  the  same  proportion  as  it  recedes  from  the  heart. 
It  is  driven  rapidly  through  the  larger  trunks,  more  slowly  through 
those  of  medium  size,  and  more  slowly  still  as  it  approaches  the 
termination  of  the  arterial  system  and  the  commencement  of  the 
capillaries. 

The  movement  of  the  blood  through  the  arteries  is  primarily  caused 
by  the  contractions  of  the  heart ;  but  is,  at  the  same  time,  regulated 
and  modified  by  the  elasticity  of  the  vessels.  The  mode  in  which 
the  arterial  circulation  takes  place  is  as  follows.  The  arterial  sys- 
tem is,  as  we  have  seen,  a  vast  and  connected  ramification  of  tubular 
canals,  which  may  be  regarded  as  a  great  vascular  cavity,  divided 
and  subdivided  from  within  outward  by  the  successive  branching 
of  its  vessels,  but  communicating  freely  with  the  heart  and  aorta 
at  one  extremity,  and  with  the  capillary  plexus  at  the  other; 
and  this  vascular  system  is  filled  everywhere  with  the  circulating 
fluid.  At  the  time  of  the  heart's  contraction,  the  muscular  walls  of 
the  ventricle  act  powerfully  upon  its  fluid  contents.  The  auriculo- 
ventricular  valves  at  the  same  time  shutting  back  and  preventing 
the  blood  from  regurgitating  into  the  ventricle,  it  is  forced  out 
through  the  aortic  orifice.  A  charge  of  blood  is  therefore  driven 
into  the  arterial  ramifications,  distending  their  walls  by  the  addi- 
tional quantity  of  fluid  forced  into  their  cavities.  When  the  ven- 
tricle immediately  afterward  relaxes,  the  active  distending  force  is 
removed;  and  the  elastic  arterial  walls,  reacting  upon  their  contents, 
would  force  the  blood  back  again  into  the  heart,  were  it  not  for  the 
semilunar  valves,  which  shut  together  and  close  the  aortic  orifice. 
The  blood  is  therefore  urged  onward,  under  the  pressure  of  the 
arterial  elasticity,  into  the  capillary  system.  When  the  arteries 
have  thus  again  partially  emptied  themselves,  and  returned  to  their 
original  dimensions,  they  are  again  distended  by  another  contraction 
of  the  heart.  In  this  manner  a  succession  of  impulses  or  distensions 
is  produced,  which  alternates  with  the  reaction  or  subsidence  of  the 
vessels,  and  which  can  be  felt  throughout  the  body,  wherever  the 
arterial  ramifications  penetrate.  This  phenomenon  is  known  by 
the  name  of  the  arterial  pulse. 

When  the  blood  is  thus  driven  by  the  cardiac  pulsations  into  the 
arteries,  the  vessels  are  not  only  distended  laterally,  but  are  elongated 
as  well  as  widened,  and  enlarged  in  every  direction.     Particularly 


THE    AUTEKIES    AND    THE    ARTEKIAL    CIRCULATION.      283 

when  the  vessel  takes  a  curved  or  serpentine  course,  its  elongation 
and  the  increase  of  its  curvatures  may  be  observed  at  every  pulsa- 
tion. This  may  be  seen,  for  example,  in  the  temporal,  or  even 
in  the  radial  arteries,  in  emaciated  persons.  It  is  also  very  well 
seen  in  the  mesenteric  arteries,  when  the  abdomen  is  opened  in  the 
living  animal.  At  every  contraction  of  the  heart  the  curves  of 
the  artery  on  each  side  become  more  strongly  pronounced.  (Fig. 
92.)  The  vessel  even  rises  up  partially  out  of  its 
bed,  particularly  where  it  runs  over  a  bony  sur-  '^' 

face,  as  in  the  case  of  the  radial  artery.  In  old 
persons  the  curves  of  the  vessels  become  perma- 
nently enlarged  from  frequent  distension ;  and  all 
the  arteries  tend  to  assume,  with  the  advance  of 
age,  a  more  serpentine  and  even  spiral  course. 

But  the  arterial  pulse  has  certain  other  pecu- 
liarities which  deserve  a  special  notice.  In  the 
first  place,  if  we  place  one  finger  upon  the  chest 
at  the  situation  of  the  apex  of  the  heart,  and  an- 
other upon  the  carotid  artery  at  the  middle  of 
the  neck,  we  can  distinguish  little  or  no  difference 
in  time  between  the  two  impulses.  The  disten-  Eionsration  and  cnrva- 
sion  of  the  carotid  seems  to  take  place  at  the  p"pls°ation^^^*^  ^'' 
same  instant  with  the  contraction  of  the  heart. 
But  if  the  second  finger  be  placed  upon  the  temporal  artery,  instead 
of  the  carotid,  there  is  a  perceptible  interval  between  the  two  beats. 
The  impulse  of  the  temporal  artery  is  felt  a  little  later  than  that  of 
the  heart.  In  the  same  way  the  pulse  of  the  radial  artery  at  the 
wrist  seems  a  little  later  than  that  of  the  carotid,  and  that  of  the 
posterior  tibial  at  the  ankle  joint  a  little  later  than  that  of  the  radial. 
So  that,  the  greater  the  distance  from  the  heart  at  which  the  artery 
is  examined,  the  later  is  the  pulsation  perceived  by  the  finger  laid 
upon  the  vessel. 

But  it  has  been  conclusively  shown,  particularly  by  the  investi- 
gations of  M.  Marey,'  that  this  difference  in  time  of  the  arterial 
pulsations,  in  different  parts  of  the  body,  is  rather  relative  than 
absolute.  By  the  contraction  of  the  heart,  the  impulse  is  commu- 
nicated at  the  same  instant  to  all  parts  of  the  arterial  system ;  but 
the  apparent  difference  between  them,  in  this  respect,  depends  upon 
the  fact,  that,  although  all  the  arteries  begin  to  be  distended  at  the 

'  Dr.  Brown-Sequard's  Journal  de  Physiologie,  April,  1859. 


284  THE    CIRCULATION. 

same  moment,  yet  those  nearest  the  heart  are  distended  suddenly 
and  rapidly,  while  for  those  at  a  distance,  the  distension  takes  place 
more  slowly  and  gradually.  Thus  the  impulse  given  to  the  finger, 
which  marks  the  condition  of  maximum  distension  of  the  vessel, 
occurs  a  little  later  at  a  distance  from  the  heart,  than  in  its  imme- 
diate proximity. 

This  modification  of  the  arterial  pulse  is  produced  in  the  follow- 
ing way : — 

The  contraction  of  the  left  ventricle  is  a  brusque,  vigorous  and 
sudden  motion.  The  charge  of  blood,  thus  driven  into  the  arterial 
system,  meeting  with  a  certain  amount  of  resistance  from  the  fluid 
already  filling  the  vessels,  does  not  instantly  displace  and  force 
onward  a  quantity  of  blood  equal  to  its  own  mass,  but  a  large 
proportion  of  its  force  is  used  in  expanding  the  distensible  walls 
of  the  vessels.  In  the  immediate  neighborhood,  therefore,  the 
expansion  of  the  arteries  is  sudden  and  momentary,  like  the  con- 
traction of  the  heart  itself.  But  this  expansion  requires  for  its 
completion  a  certain  expenditure,  both  of  force  and  time ;  so  that 
at  a  little  distance  farther  on,  the  vessel  is  neither  distended  to  the 
same  degree  nor  with  the  same  rapidity.  At  the  more  distant 
point,  accordingly,  the  arterial  impulse  is  less  powerful  and  arrives 
more  slowly  at  its  maximum. 

On  the  other  hand,  when  the  heart  becomes  relaxed,  the  artery 
in  its  immediate  neighborhood  contracts  upon  the  blood  by  its  own 
elasticity ;  and  as  its  contraction  at  this  time  meets  with  no  other 
resistance  than  that  of  the  blood  in  the  smaller  vessels  beyond,  it 
drives  a  portion  of  its  own  blood  into  them,  and  thus  supplies  these 
vessels  with  a  certain  degree  of  distending  force  even  in  the  inter- 
vals of  the  heart's  action.  Thus  the  difference  in  size  of  the  carotid 
artery,  at  the  two  periods  of  the  heart's  contraction  and  its  relaxa- 
tion, is  very  marked ;  for  the  degree  of  its  distension  is  great  when 
the  heart  contracts,  and  its  own  reaction  afterward  empties  it  of 
blood  to  a  very  considerable  extent.  But  in  the  small  branches  of 
the  radial  or  ulnar  artery,  there  is  less  distension  at  the  time  of  the 
cardiac  contraction,  because  this  force  has  been  partly  expended  in 
overcoming  the  elasticity  of  the  larger  vessels ;  and  there  is  less 
emptying  of  the  vessel  afterward,  because  it  is  still  kept  partially 
filled  by  the  reaction  of  the  aorta  and  its  larger  branches.  In  other 
words,  there  is  progressively  less  variation  in  size,  at  the  periods  of 
distension  and  collapse,  for  the  smaller  and  distant  arteries  than  for 
those  which  are  larger  and  nearer  the  heart. 


THE    ARTERIES    AND    THE    ARTERIAL    CIRCULATION,      285 

Mr.  Marey  lias  illustrated  these  facts  by  an  exceedingly  ingenious 
and  effectual  contrivance.  He  attached  to  the  pipe  of  a  small  forcing 
pump,  to  be  worked  by  alternate  strokes  of  the  piston,  a  long  elastic 
tube  open  at  the  farther  extremity.  At  different  points  upon  this 
tube  there  rested  little  movable  levers,  which  were  raised  by  the 
distension  of  the  tube  whenever  water  was  driven  into  it  by  the 
forcing  pump.  Each  lever  carried  upon  its  extremity  a  small  pen- 
cil, which  marked  upon  a  strip  of  paper,  revolving  with  uniform 
rapidity,  the  lines  produced  by  its  alternate  elevation  and  depression. 
By  these  curves,  therefore,  both  the  extent  and  rapidity  of  distension 
of  different  parts  of  the  elastic  tube  were  accurately  registered. 
The  curves  thus  produced  are  as  follows : — 

Fig.  93. 


CnavES  OP  THE  Arterial  Pulsation,  as  ilhistrated  by  M.  Marey's  experiment.— 1.  Near 
the  distending  force.     2.  At  a  distance  from  it.     3.  Still  farther  removed. 

It  will  be  seen  that  the  whole  time  of  pulsation  is  everywhere  of 
equal  length,  and  that  the  distension  everywhere  begins  at  the  same 
moment.  But  at  the  beginning  of  the  tube  the  expansion  is  wide 
and  sudden,  and  occupies  only  a  sixth  part  of  the  entire  pulsation, 
while  all  the  rest  is  taken  up  by  a  slow  reaction.  At  the  more 
remote  points,  however,  the  period  of  expansion  becomes  longer 
and  that  of  collapse  shorter ;  until  at  3  the  two  periods  are  com- 
pletely equalized,  and  the  amount  of  expansion  is  at  the  same  time 
reduced  one-half  Thus,  the  farther  the  blood  passes  from  the  heart 
outward,  the  more  uniform  is  its  flow,  and  the  more  moderate  the 
distension  of  the  arteries. 

Owing  to  the  alternating  contractions  and  relaxations  of  the  heart, 
accordingly,  the  blood  passes  through  the  arteries,  not  in  a  steady 
stream,  but  in  a  series  of  welling  impulses ;  and  the  hemorrhage 
from  a  wounded  artery  is  readily  distinguished  from  venous  or 
capillary  hemorrhage  by  the  fact  that  the  blood  flows  in  successive 
jets,  as  well  as  more  rapidly  and  abundantly.  If  a  puncture  be 
made  in  the  walls  of  the  ventricle,  and  a  slender  canula  introduced, 


2b6  THE    CIRCULATION. 

the  flow  of  the  blood  through  it  is  seen  to  he  entirely  intermittent. 
A  strong  jet  takes  place  at  each  ventricular  contraction,  and  at  each 
relaxation  the  flow  is  completely  interrupted.  If  the  puncture  be 
made,  however,  in  any  of  the  large  arteries  near  the  heart,  the  flow 
of  blood  through  the  orifice  is  no  longer  intermittent,  but  is  con- 
tinuous ;  only  it  is  very  much  stronger  at  the  time  of  ventricular 
contraction,  and  diminishes,  though  it  does  not  entirely  cease,  at 
the  time  of  relaxation.  If  the  blood  were  driven  through  a  series 
of  perfectly  rigid  and  unyielding  tubes,  its  flow  would  be  every- 
where intermittent ;  and  it  would  be  delivered  from  an  orifice  situ- 
ated at  any  point,  in  perfectly  interrupted  jets.  But  the  arteries 
are  yielding  and  elastic;  and  this  elasticity,  as  we  have  already 
explained,  moderates  the  force  of  the  separate  arterial  pulsations, 
and  gradually  fuses  them  with  each  other.  The  interrupted  or 
pulsating  character  of  the  arterial  current,  therefore,  which  is 
strongly  pronounced  in  the  immediate  vicinity  of  the  heart,  becomes 
gradually  lost  and  equalized,  during  its  passage  through  the  vessels, 
until  in  the  smallest  arteries  it  is  nearly  imperceptible. 

The  same  effect  of  an  elastic  medium  in  equalizing  the  force  of 
an  interrupted  current  may  be  shown  by  fitting  to  the  end  of  a 
common  syringe  a  long  glass  or  metallic  tube.  "Whatever  be  the 
length  of  the  inelastic  tubing,  the  water  which  is  thrown  into  one 
extremity  of  it  by  the  syringe  will  be  delivered  from  the  other  end 
in  distinct  jets,  corresponding  with  the  strokes  of  the  piston ;  but  if 
the  metallic  tube  be  replaced  by  one  of  India  rubber,  of  sufficient 
length,  the  elasticity  of  this  substance  merges  the  force  of  the  sepa- 
rate impulses  into  each  other,  and  the  water  is  driven  out  from  the 
farther  extremity  in  a  continuous  stream. 

The  elasticity  of  the  arteries,  however,  never  entirely  equalizes 
the  force  of  the  separate  cardiac  pulsations,  since  a  pulsating  cha- 
racter can  be  seen  in  the  flow  of  the  blood  through  even  the  smallest 
arteries,  under  the  microscope  ;  but  this  pulsating  character  dimi- 
nishes very  considerably  from  the  heart  outward,  and  the  current 
becomes  much  more  continuous  in  the  smaller  vessels  than  in  the 
larger. 

The  primary  cause,  therefore,  of  the  motion  of  the  blood  in  the 
arteries  is  the  contraction  of  the  ventricles,  which,  by  driving  out 
the  blood  in  interrupted  impulses,  distends  at  every  stroke  the 
whole  arterial  system.  But  the  arterial  pulse  is  not  exactly  syn- 
chronous everywhere  with  the  beat  of  the  heart ;  since  a  certain 
amount  of  time  is  required  to  propagate  the  blood-wave  from  the 


THE    AKTERIES    AND    TKE    ARTERIAL    CIRCULATION.      287 

centre  of  tlie  circulation  outward.  The  pulse  of  the  radial  artery 
at  the  wrist  is  perceptibly  later  than  that  of  the  heart ;  and  the 
pulse  of  the  posterior  tibial  at  the  ankle,  again,  perceptibly  later 
than  that  at  the  wrist.  The  arterial  circulation,  accordingly,  is  not 
an  entirely  simple  phenomenon ;  but  is  made  up  of  the  combined 
efi'ects  of  two  different  physical  forces.  In  the  first  place,  there  is 
the  elasticity  of  the  entire  arterial  system,  by  which  the  blood  is 
subjected  to  a  constant  and  uniform  pressure,  quite  independent  of 
the  action  of  the  heart.  Secondly,  there  is  the  alternating  contrac- 
tion and  relaxation  of  the  heart,  by  which  the  blood  is  driven  in 
rapid  and  successive  impulses  from  the  centre  of  the  circulation,  to 
be  thence  distributed  throughout  the  body. 

The  passage  of  the  blood  through  the  arterial  system  takes  place 
under  a  certain  degree  of  constant  pressure.  For  these  vessels  being 
everywhere  elastic,  and  filled  with  blood,  they  constantly  tend  to 
react,  more  or  less  vigorously,  and  to  compress  the  circulating  fluid 
which  they  contain.  If  any  one  of  the  arteries,  accordingly,  be 
opened  in  the  living  animal,  and  a  glass  tube  inserted,  the  blood 
will  immediately  be  seen  to  rise  in  the  tube  to  a  height  of  about 
five  and  a  half  or  six  feet,  and  will  remain  at  that  level ;  thus  indi- 
cating the  pressure  to  which  it  was  subjected  in  the  interior  of  the 
vessels.  This  constant  pressure,  which  is  thus  due  to  the  reaction 
of  the  entire  arterial  system,  is  known  as  the  arterial  pressure. 

The  degree  of  arterial  pressure  may  be  easily  measured  by  con- 
necting the  open  artery,  by  a  flexible  tube,  with  a  small  reservoir 
of  mercury,  which  is  provided  with  a  narrow  upright  glass  tube, 
open  at  its  upper  extremity.  "When  the  blood,  therefore,  urged  by 
the  reaction  of  the  arterial  walls,  presses  upon  the  surface  of  the 
mercury  in  the  receiver,  the  mercury  rises  in  the  upright  tube,  to 
a  corresponding  height.  By  the  use  of  this  instrument  it  is  seen, 
in  the  first  place,  that  the  arterial  pressure  is  nearly  the  same  all 
over  the  body.  Since  the  cavit}''  of  the  arterial  system  is  every- 
where continuous,  the  pressure  must  necessarily  be  communicated, 
by  the  blood  in  its  interior,  equally  in  all  directions.  Accordingly, 
the  constant  pressure  is  the  same,  or  nearly  so,  in  the  larger  and  the 
smaller  arteries,  in  those  nearest  the  heart,  and  those  at  a  distance. 
This  constant  pressure  averages,  in  the  higher  quadrupeds,  six 
inches  of  mercury,  which  is  equivalent  to  from  five  and  a  half  to 
six  feet  of  blood. 

It  is  also  seen,  however,  in  employing  such  an  instrument,  that 
the  level  of  the  mercury,  in  the  upright  tube,  is  not  perfectly  steady, 


288  THE    CIRCULATION. 

but  rises  and  falls  with  the  pulsations  of  the  heart.  Thus,  at  every 
contraction  of  the  ventricle,  the  mercury  rises  for  about  half  an 
inch,  and  at  every  relaxation  it  falls  to  its  previous  level.  Thus  the 
instrument  becomes  a  measure,  not  only  for  the  constant  pressure  of 
the  arteries,  but  also  for  the  intermitting  pressure  of  the  heart ;  and 
on  that  account  it  has  received  the  name  of  the  cardiometer.  It  is 
seen,  accordingly,  that  each  contraction  of  the  heart  is  superior  in 
force  to  the  reaction  of  the  arteries  by  about  one-twelfth ;  and  these 
vessels  are  kept  filled  by  a  succession  of  cardiac  pulsations,  and 
discharge  their  contents  in  turn  into  the  capillaries,  by  their  own 
elastic  reaction. 

The  rapidity  with  which  the  blood  circulates  through  the  arterial 
system  is  very  great.  Its  velocity  is  greatest  in  the  immediate 
neighborhood  of  the  heart,  and  diminishes  somewhat  as  the  blood 
recedes  farther  and  farther  from  the  centre  of  the  circulation.  This 
diminution  in  the  rapidity  of  the  arterial  current  is  due  to  the  suc- 
cessive division  of  the  aorta  and  its  primary  branches  into  smaller 
and  smaller  ramifications,  by  which  the  total  calibre  of  the  arterial 
system,  as  we  have  already  mentioned,  is  somewhat  increased.  The 
blood,  therefore,  flowing  through  a  larger  space  as  it  passes  outward, 
necessarily  moves  more  slowly.  At  the  same  time  the  increased 
extent  of  the  arterial  parietes  with  which  the  blood  comes  in  con- 
tact, as  well  as  the  mechanical  obstacle  arising  from  the  division  of 
the  vessels  and  the  separation  of  the  streams,  undoubtedly  contri- 
butes more  or  less  to  retard  the  currents.  The  mechanical  obstacle, 
however,  arising  from  the  friction  of  the  blood  against  the  walls  of 
the  vessels,  which  would  be  very  serious  in  the  case  of  water  or  any 
similar  fluid  flowing  through  glass  or  metallic  tubes,  has  compara- 
tively little  effect  on  the  rapidity  of  the  arterial  circulation.  This 
can  readily  be  seen  by  microscopic  examination  of  any  transparent 
and  vascular  tissue.  The  internal  surface  of  the  arteries  is  so  smooth 
and  yielding,  and  the  consistency  of  the  circulating  fluid  so  accu- 
rately adapted  to  that  of  the  vessels  which  contain  it,  that  the 
retarding  effects  of  friction  are  reduced  to  a  minimum,  and  the 
blood  in  flowing  through  the  vessels  meets  with  the  least  possible 
resistance. 

It  is  owing  to  this  fact  that  the  arterial  circulation,  though  some- 
what slower  toward  the  periphery  than  near  the  heart,  yet  retains 
a  very  remarkable  velocity  throughout ;  and  even  in  arteries  of  the 
minutest  size  it  is  so  rapid  that  the  shape  of  the  blood-globules  can- 
not be  distinguished  in  it  on  microscopic  examination,  but  only  a 


THE    AETERIES    AND    THE    ARTERIAL    CIRCULATION.      289 

mingled  current  shooting  forward  with  increased  velocity  at  every 
cardiac  pulsation.  Volkmann,  in  Germany,  has  determined,  by  a 
very  ingenious  contrivance,  the  velocity  of  the  current  of  blood  in 
some  of  the  large  sized  arteries  in  dogs,  horses,  and  calves.  The 
instrument  which  he  employed  (Fig.  94)  consisted  of  a  metallic 
cylinder  (a),  with  a  perforation  running  from  end  to  end,  and  cor- 
responding in  size  with  the  artery  to  be  examined.  The  artery 
was  divided  transversely,  and  its  cardiac  extremity  fastened  to  the 
upper  end  (6)  of  the  instrument,  while  its  peripheral  extremity  was 


Fig.  94. 


Fig.  95. 


VoLKM  Ann's  ApPARATns  for  measuring  thp  rapidity  of  the  arterial  circulation. 


fastened  in  the  same  manner  to  the  lower  end  (c).  The  blood 
accordingly  still  kept  on  its  usual  course ;  only  passing  for  a  short 
distance  through  the  artificial  tube  (a),  between  the  divided  extremi- 
ties of  the  artery.  The  instrument,  however,  was  provided,  as  shown 
in  the  accompanying  figures,  with  two  transverse  cylindrical  plugs, 
also  perforated ;  and  arranged  in  such  a  manner,  that  when,  at  a 
19 


290  THE    CIRCULATIOX. 

given  signal,  the  two  plugs  were  suddenly  turned  in  opposite 
directions,  the  stream  of  blood  would  be  turned  out  of  its  course 
(Fig,  95),  and  made  to  traverse  a  long  bent  tube  of  glass  {d,  d,  d), 
before  again  finding  its  way  back  to  the  lower  portion  of  the  artery. 
In  this  way  the  distance  passed  over  by  the  blood  in  a  given  time 
could  be  readily  measured  upon  a  scale  attached  to  the  side  of  the 
glass  tube.  Yolkmann  found,  as  the  average  result  of  his  obser- 
vations, that  the  blood  moves  in  the  carotid  arteries  of  warm-blooded 
quadrupeds  with  a  velocity  of  12  inches  per  second. 

VENOUS   CIRCULATION. 

The  veins,  which  collect  the  blood  from  the  tissues  and  return  it 
to  the  heart,  are  composed,  like  the  arteries,  of  three  coats ;  an  inner, 
middle,  and  exterior.  In  structure,  they  differ  from  the  arteries  in 
containing  a  much  smaller  quantity  of  muscular  and  elastic  fibres, 
and  a  larger  proportion  of  simple  condensed  areolar  tissue.  They 
are  consequently  more  flaccid  and  compressible  than  the  arteries, 
and  less  elastic  and  contractile.  They  are  furthermore  distin- 
guished, throughout  the  limbs,  neck,  and  external  portions  of  the 
head  and  trunk,  by  being  provided  with  valves,  consisting  of  fibrous 
sheets  arranged  in  the  form  of  festoons,  and  so  placed  in  the  cavity 
of  the  vein  as  to  allow  the  blood  to  pass  readily  from  the  periphery 
toward  the  heart,  while  they  prevent  altogether  its  reflux  in  an 
opposite  direction. 

Although  the  veins  are  provided  with  walls  which  are  very  much 
thinner  and  less  elastic  than  those  of  the  arteries,  yet,  contrary  to 
what  we  might  expect,  their  capacity  for  resistance  to  pressure  is 
equal,  or  even  superior,  to  that  of  the  arterial  tubes.  Milne  Ed- 
wards' has  collected  the  results  of  various  experiments,  which  show 
that  the  veins  will  sometimes  resist  a  pressure  which  is  sufiicient  to 
rupture  the  walls  of  the  arteries.  In  one  instance  the  jugular  vein 
supported,  without  breaking,  a  pressure  equal  to  a  column  of  water 
148  feet  in  height ;  and  in  another,  the  iliac  vein  of  a  sheep  resisted 
a  pressure  of  more  than  four  atmospheres.  The  portal  vein  was 
found  capable  of  resisting  a  pressure  of  six  atmospheres ;  and  in 
one  case,  in  which  the  aorta  of  a  sheep  was  ruptured  by  a  pressure 
of  158  pounds,  the  vena  cava  of  the  same  animal  supported  a  pres- 
sure equal  to  176  pounds. 

'  LeQons  sur  la  Physiologie,  &c.,  vol.  iv.  p.  301. 


VENOUS    CIRCULATION.  291 

This  resistance  of  the  veins  is  to  be  attributed  to  the  large  pro- 
portion of  white  fibrous  tissue  which  enters  into  their  composition  ; 
the  same  tissue  which  forms  nearly  the  whole  of  the  tendons  and 
fasciae,  and  which  is  distinguished  by  its  density  and  unyielding 
nature. 

The  elasticity  of  the  veins,  however,  is  much  less  than  that  of  the 
arteries.  When  they  are  filled  with  blood,  they  enlarge  to  a  certain 
size,  and  collapse  again  when  the  pressure  is  taken  off;  but  they  do 
not  react  by  virtue  of  an  elastic  resilience,  or,  at  least,  only  to  a 
slight  extent,  as  compared  with  the  arteries.  Accordingly,  when 
the  arteries  are  cut  across,  and  emptied  of  blood,  they  still  remain 
open  and  pervious,  retaining  the  tubular  form,  on  account  of  the 
elasticity  of  their  walls ;  while,  if  the  veins  be  treated  in  the  same 
way,  their  sides  simply  fall  together  and  remain  in  contact  with  each 
other. 

Another  peculiarity  of  the  venous  system  is  the  abundance  of 
the  separate  channels,  which  it  affords,  for  the  flow  of  blood  from 
the  periphery  towards  the  centre.  The  arteries  pass  directly  from 
the  heart  outward,  each  separate  branch,  as  a  general  rule,  going 
to  a  separate  region,  and  supplying  that  part  of  the  body  with 
all  the  blood  which  it  requires  ;  so  that  the  arterial  system  is  kept 
constantly  filled  to  its  entire  capacity  with  the  blood  which  passes 
through  it.  But  that  is  not  the  case  with  the  veins.  In  injected 
preparations  of  the  vascular  system,  we  have  often  two,  three, 
four,  or  even  five  veins,  coming  together  from  the  same  region  of 
the  body.  There  are  also  abundant  inosculations  between  the  dif- 
ferent veins.  The  deep  veins  which  accompany  the  brachial  artery 
inosculate  freely  with  each  other,  and  also  with  the  superficial  veins 
of  the  arm.  In  the  veins  coming  from  the  head,  we  have  the  ex- 
ternal jugular  communicating  with  the  thyroid  veins,  the  anterior 
jugular,  and  the  brachial  veins.  The  external  and  internal  jugulars 
communicate  with  each  other,  and  the  two  thyroid  veins  also  form 
an  abundant  plexus  in  front  of  the  trachea. 

Thus  the  blood,  coming  from  the  extremities  toward  the  heart, 
flows,  not  in  a  single  channel,  but  in  many  channels ;  and  as  these 
channels  communicate  freely  with  each  other,  the  blood  passes  some- 
times through  one  of  them,  and  sometimes  through  another. 

The  flow  of  blood  through  the  veins  is  less  powerful  and  regular 
than  that  through  the  arteries.  It  depends  on  the  combined  action 
of  three  difierent  forces. 


292  THE    CIRCULATION. 

1.  The  force  of  aspiration  of  the  thorax. — When  the  chest  expands 
by  the  lifting  of  the  ribs  and  the  descent  of  the  diaphragm,  its 
movement,  of  course,  tends  to  diminish  the  pressure  exerted  upon 
its  contents,  and  so  has  the  effect  of  drawing  into  the  thoracic  cavity 
all  the  fluids  which  can  gain  access  to  it.  The  expanded  cavity  is 
principally  filled  by  the  air.  which  passes  in  through  the  trachea 
and  fills  the  bronchial  tubes  and  the  pulmonary  vesicles.  But  the 
blood  in  the  veins  is  also  drawn  into  the  chest  at  the  same  time  and 
by  the  same  force.  This  force  of  aspiration,  exerted  by  the  expan- 
sion of  the  chest,  is  gentle  and  uniform  in  character,  like  the  move- 
ments of  respiration  themselves.  Accordingly  its  influence  is  ex- 
tended, without  doubt,  to  the  farthest  extremities  of  the  venous 
system,  the  blood  being  gently  solicited  toward  the  heart,  at  each 
expansion  of  the  chest,  without  any  visible  alteration  in  the  size  of 
the  veins,  which  are  filled  up  from  behind  as  fast  as  they  are  emptied 
in  front. 

But  if  the  movement  of  inspiration  be  sudden  and  violent,  instead 
of  gentle  and  easy,  a  different  effect  is  produced.  For  then  the  walls 
of  the  veins,  which  are  thin  and  flaccid,  cannot  retain  their  position, 
but  collapse  under  the  external  pressure  too  rapidly  to  allow  the 
blood  to  flow  in  from  behind.  In  this  case,  therefore,  the  vein  is 
simply  emptied  in  the  immediate  neighborhood  of  the  chest,  but 
the  entire  venous  circulation  is  not  assisted  by  the  movement. 

The  same  difference  in  the  effect  of  an  easy  and  a  violent  suction 
movement,  may  be  readily  shown  by  attaching  to  the  nozzle  of  an 
air-tight  syringe  a  flexible  elastic  tube  with  thin  walls,  and  placing 
the  other  extremity  of  the  tube  under  water.  If  the  piston  of  the 
syringe  be  now  withdrawn  with  a  gentle  and  gradual  motion,  the 
water  will  be  readily  drawn  up  into  the  tube,  while  the  tube  itself 
suffers  no  visible  change ;  but  if  the  suction  movement  be  made 
rapid  and  violent,  the  tube  will  collapse  instantly  under  the  pres- 
sure of  the  air,  and  will  fail  to  draw  the  water  into  its  cavity. 

A  similar  effect  shows  itself  in  the  living  body.  If  the  jugular 
or  subclavian  vein  be  exposed  in  a  dog  or  cat,  it  will  be  seen  that 
while  the  movements  of  respiration  are  natural  and  easy  no  fluc- 
tuation in  the  vein  can  be  perceived.  But  as  soon  as  the  respira- 
tion becomes  disturbed  and  laborious,  then  at  each  inspiration  the 
vein  is  collapsed  and  emptied ;  while  during  expiration,  the  chest 
being  strongly  compressed  and  the  inward  flow  of  the  blood  arrested, 
the  vein  becomes  turgid  with  blood  which  accumulates  in  it  from 
behind.     In  young  children,  also,  the  spasmodic  movements  of  res- 


VEXOUS    CIRCULATION, 


29^ 


piration  in  crying  produce  a  similar  turgescence  and  engorgement 
of  the  large  veins  during  expiration,  while  they  are  momentarily 
emptied  during  the  hurried  and  forcible  inspiration. 

In  natural  and  quiet  respiration,  therefore,  the  movements  of  the 
chest  hasten  and  assist  the  venous  circulation ;  but  in  forced  or 
laborious  respiration,  they  do  not  assist  and  may  even  retard  its  flow. 

2.  The  contraction  of  the  voluntarg  muscles. — The  veins  which 
convey  the  blood  through  the  limbs,  and  the  parietes  of  the  head 
and  trunk,  lie  among  voluntary  muscles,  which  are  more  or  less 
constantly  in  a  state  of  alternate  contraction  and  relaxation.  At 
every  contraction  these  muscles  become  swollen  laterally,  and,  of 
course,  compress  the  veins  which  are  situated  between  them.  The 
blood,  driven  out  from  the  vein  by  this  pressure,  cannot  regurgitate 
toward  the  capillaries,  owing  to  the  valves,  already  described,  which 
shut  back  and  prevent  its  reflux.  It  is  accordingly  forced  onward 
toward  the  heart;  and  when  the  muscle  relaxes  and  the  vein  is 
liberated  from  pressure,  it  again  fills  up  from  behind,  and  the  cir- 
culation goes  on  as  before.  This  force  is  a  very  efficient  one  in 
producing  the  venous  circulation ;  since  the  voluntary  muscles  are 
more  or  less  active  in  every  position  of  the  body,  and  the  veins 
constantly  liable  to  be  compressed  by  them.     It  is  on  this  account 


Fig.  96. 


Fig.  97. 


V  K  I  N   with  valves  opeu. 


Vein  witli  valves  closed;  stream  of 
blood  passing  off  by  a  lateral  channel. 


that  the  veins,  in  the  external  parts  of  the  body,  communicate  so 
freely  with  each  other  by  transverse  branches ;  in  order  that  the 
current  of  blood,  which  is  momentarily  excluded  from  one  vein  by 


294  THE    CIRCULATION. 

the  pressure  of  the  muscles,  may  readily  find  a  passage  through 
others,  which  communicate  by  cross  branches  with  the  first.  (Figs. 
96  and  97.) 

3.  The  force  of  the  capillary  circulation. — This  last  cause  of  the 
motion  of  the  blood  through  the  veins  is  the  most  important  of  all, 
as  it  is  the  only  one  which  is  constantly  and  universally  active.  In 
fish,  for  example,  respiration  is  performed  altogether  by  gills ;  and 
in  reptiles  the  air  is  forced  down  into  the  lungs  by  a  kind  of  deglu- 
tition, instead  of  being  drawn  in  by  the  expansion  of  the  chest.  In 
neither  of  these  classes,  therefore,  can  the  movements  of  respiration 
assist  mechanically  in  the  circulation  of  the  blood.  In  the  splanch- 
nic cavities,  again,  of  all  the  vertebrate  ariimals,  the  veins  coming 
from  the  internal  organs,  as,  for  example,  the  cerebral,  pulmonary, 
portal,  hepatic,  and  renal  veins,  are  unprovided  with  valves ;  and 
the  passage  of  the  blood  through  them  cannot  therefore  be  effected 
by  any  lateral  pressure.  The  circulation,  however,  constantly  going 
on  in  the  capillaries,  everywhere  tends  to  crowd  the  radicles  of  the 
veins  with  blood ;  and  this  vis  a  tergo,  or  pressure  from  behind,  fills 
the  whole  venous  system  by  a  constant  and  steady  accumulation. 
So  long,  therefore,  as  the  veins  are  relieved  of  blood  at  their  cardiac 
extremity  by  the  regular  pulsations  of  the  heart,  there  is  no  back- 
ward pressure  to  oppose  the  impulse  derived  from  the  capillary  cir- 
culation ;  and  the  movement  of  the  blood  through  the  veins  continues 
in  a  steady  and  uniform  course. 

With  regard  to  the  rapidity  of  the  venous  circulation,  no  direct 
results  have  been  obtained  by  experiment.  Owing  to  the  flaccidity 
of  the  venous  parietes,  and  the  readiness  with  which  the  flow  of 
blood  through  them  is  disturbed,  it  is  not  possible  to  determine  this 
point  for  the  veins,  in  the  same  manner  as  it  has  been  determined 
for  the  arteries.  The  only  calculation  which  has  been  made  in  this 
respect  is  based  upon  a  comparison  of  the  total  capacity  of  the 
arterial  and  venous  systems.  As  the  same  blood  which  passes  out- 
ward through  the  arteries,  passes  inward  again  through  the  veins, 
the  rapidity  of  its  flow  in  each  must  be  in  inverse  proportion  to  the 
capacity  of  the  two  sets  of  vessels.  That  is  to  say,  a  quantity  of 
blood  which  would  pass  in  a  given  time,  with  a  velocity  of  x, 
through  an  opening  equal  to  one  square  inch,  would  pass  during 
the  same  time  through  an  opening  equal  to  two  square  inches,  with 
a  velocity  of  | ;  and  would  require,  on  the  other  hand,  a  velocity 
of  2  X,  to  pass  in  the  same  time  through  an  opening  equal  to  one- 
half  a  square  inch.     Now  the  capacity  of  the  entire  venous  system, 


THE    CAPILLARY    CIRCULATION.  295 

when  distended  by  injection,  is  about  twice  as  great  as  that  of  the 
entire  arterial  system.  During  life,  however,  the  venous  system  is 
at  no  time  so  completely  filled  with  blood  as  is  the  case  with  the 
arteries,  and,  making  allowance  for  this  difference,  we  find  that  the 
entire  quantity  of  venous  blood  is  to  the  entire  quantity  of  arterial 
blood  nearly  as  three  to  two.  The  velocity  of  the  venous  blood, 
as  compared  with  that  of  the  arterial,  is  therefore  as  two  to  three ; 
or  about  8  inches  per  second.  It  will  be  understood,  however,  that 
this  calculation  is  altogether  approximative,  and  not  exact ;  since 
the  venous  current  varies,  according  to  many  different  circumstances, 
in  different  parts  of  the  body ;  being  slower  near  the  capillaries, 
and  more  rapid  near  the  heart.  It  expresses,  however,  with  suffi- 
cient accuracy,  the  relative  velocity  of  the  arterial  and  venous  cur- 
rents, at  corresponding  parts  of  their  course. 


THE   CAPILLARY  CIRCULATION". 

The  capillary  bloodvessels  are  minute  inosculating  tubes,  which 
permeate  the  vascular  organs  in  every  direction,  and  bring  the 
blood  into  intimate  contact  with  the  substance  of  the  tissues.  They 
are  continuous  with  the  terminal  ramifications  of  the  arteries  on 
the  one  hand,  and  with  the  com- 
mencing rootlets  of  the  veins  on 
the  other.  They  vary  somewhat 
in  size  in  different  organs,  and  in 
different  species  of  animals ;  their 
average  diameter  in  the  human 
subject  being  a  little  over  3  oVo  of 
an  inch.  They  are  composed  of 
a  single,  transparent,  homogene- 
ous, somewhat  elastic,  tubular 
membrane,  which  is  provided  at 
various  intervals  with  flattened, 
oval  nuclei.  As  the  smaller  arte- 
ries approach  the  capillaries,  they 
diminish  constantly  in  size  by 
successive  subdivision,  and  lose 
first  their  external  or  fibrous 
tunic.     They  are  then  composed 

only  of  the  internal  or  homogeneous  coat,  and  the  middle  or  muscu- 
lar.  (Fig.  98,  a)    The  middle  coat  then  diminishes  in  thickness, 


Small  Artrrt,  with  its  muscular  tunic 
(a),  breaking  up  into  capillaries.  From  th^pia 
mater. 


296 


THE    CIRCULATION". 


until  it  is  reduced  to  a  single  layer  of  circular,  fusiform,  unstriped, 
muscular  fibres,  which  in  their  turn  disappear  altogether,  as  the 
artery  merges  at  last  in  the  capillaries ;  leaving  only,  as  we  have 
already  mentioned,  a  simple,  homogeneous,  nucleated,  tubular  mem- 
brane, which  is  continuous  with  the  internal  arterial  tunic. 

The  capillaries  are  further  distinguished  from  both  arteries  and 
veins  by  their  frequent  inosculation.  The  arteries  constantly 
divide  and  subdivide,  as  they  pass  from  within  outward;  while 
the  veins  as  constantly  unite  with  each  other  to  form  larger  and 
less  numerous  branches  and  trunks,  as  they  pass  from  the  circum- 
ference toward  the  centre.  But  the  capillaries  simply  inosculate 
with  each  other  in  every  direction,  in  such  a  manner  as  to  form  an 
interlacing  network  or  plexus,  the  cajpillary  plexus  (Fig.  99),  which 
is  exceedingly  rich  and  abundant  in  some  organs,  less  so  in  others. 
The  spaces  included  between  the  meshes  of  the  capillary  network 
vary  also,  in  shape  as  well  as  in  size,  in  different  parts  of  the  body. 

In  the  muscular  tissue  they 
^''S-  ^^-  form  long  parallelograms ;  in 

the  areolar  tissue,  irregular 
shapeless  figures,  correspond- 
ing with  the  direction  of  the 
fibrous  bundles  of  which  the 
tissue  is  composed.  In  the 
mucous  membrane  of  the 
large  intestine,  the  capillaries 
include  hexagonal  or  nearly 
circular  spaces,  inclosing  the 
orifices  of  the  follicles.  In 
the  papillae  of  the  tongue  and 
of  the  skin,  and  in  the  tufts 
of  the  placenta,  they  are 
arranged  in  long  spiral  loops, 
and  in  the  adipose  tissue  in  wide  meshes,  among  which  the  fat 
vesicles  are  entangled. 

The  motion  of  the  blood  in  the  capillaries  may  be  studied  by 
examining  under  the  microscope  any  transparent  tissue,  of  a 
sufficient  degree  of  vascularity.  One  of  the  most  convenient  parts 
for  this  purpose  is  the  web  of  the  frog's  foot.  When  properly 
prepared  and  kept  moistened  by  the  occasional  addition  of  water 
to  the  integument,  the  circulation  Avill  go  on  in  its  vessels  for  an 
indefinite  len«?th  of  time.       The  blood  can  be  seen  entering  the 


C  A  p  r  r.  L  A  R  Y  Network  from  web  of  frog's  foot. 


THE    CAPILLARY    CIP.CU  LATION. 


297 


•ig' 


100. 


field  b}^  the  smaller  arteries,  shooting  through  them  with  great 
rapidity  and  in  successive  impulses,  and  flowing  off  again  by  the 
veins  at  a  somewhat  slow  rate.  In  the  capillaries  themselves 
the  circulation  is  considerably  less  rapid  than  in  either  the  arteries 
or  the  veins.  It  is  also  perfectly  steady  and  uninterrupted  in  its 
flow.  The  blood  passes  along  in  a  uniform  and  continuous  current, 
without  any  apparent  contraction  or  dilatation  of  the  vessels,  very 
much  as  if  it  were  flowing 
through  glass  tubes.  An- 
other very  remarkable  pe- 
culiarity of  the  capillary 
circulation  is  that  it  has  no 
definite  direction.  The  nu 
merous  streams  of  which  it 
is  composed  (Fig.  100)  do 
not  tend  to  the  right  or  to 
the  left,  nor  toward  any  one 
particular  point.  On  the 
contrary,  they  pass  above 
and  below  each  other,  at 
rififht  ansfles  to  each  other's 

O  O 

course,  or  even  in  opposite 

directions;  so  that  the  blood, 

while  in  the  capillaries,  merely  circulates   promiscuously  among 

the  tissues,  in  such  a  manner  as  to  come  intimately  in  contact  with 

every  part  of  their  substance. 

The  motion  of  the  white  and  red  globules  in  the  circulating  blood 
is  also  peculiar,  and  shows  very  distinctly  the  difference  in  their 
consistency  and  other  physical  properties.  In  the  larger  vessels 
the  red  globules  are  carried  along  in  a  dense  column,  in  the  central 
part  of  the  stream ;  while  near  the  edges  of  the  vessel  there  is  a 
transparent  space  occupied  only  by  the  clear  plasma  of  the  blood, 
in  which  no  red  globules  are  to  be  seen.  In  the  smaller  vessels, 
the  globules  pass  along  in  a  narrower  column,  two  by  two,  or 
following  each  other  in  single  file.  The  flexibility  and  semi-fluid 
consistency  of  these  globules  are  here  very  apparent,  from  the 
readiness  with  which  they  become  folded  up,  bent  or  twisted  in 
turning  corners,  and  the  ease  with  which  they  glide  through  minute 
Vjranches  of  communication,  smaller  in  diameter  than  themselves. 
The  white  globules,  on  the  other  hand,  flow  more  slowly  and  with 
greater  difficulty  through  the  vessels.     They  drag  along  the  exter- 


298  THE    CIRCULATION'. 

na]  portions  of  the  current,  and  are  sometimes  momentarily  arrested  ; 
apparently  adhering  for  a  few  seconds  to  the  internal  surface  of  the 
vessel.  Whenever  the  current  is  obstructed  or  retarded  in  any 
manner,  the  white  globules  accumulate  in  the  affected  portion,  and 
become  more  numerous  there  in  proportion  to  the  red. 

It  is  during  the  capillary  circulation  that  the  blood  serves  for 
the  nutrition  of  the  vascular  organs.  Its  fluid  portions  slowly 
transude  through  the  walls  of  the  vessels,  and  are  absorbed  by  the 
tissues  in  such  proportion  as  is  requisite  for  their  nourishment. 
The  saline  substances  enter  at  once  into  the  composition  of  the 
surrounding  parts,  generally  without  undergoing  any  change.  The 
phosphate  of  lime,  for  example,  is  taken  up  in  large  quantity  by 
the  bones  and  cartilages,  and  in  smaller  quantity  by  the  softer  parts ; 
while  the  chlorides  of  sodium  and  potassium,  the  carbonates,  sul- 
phates, &c.,  are  appropriated  in  special  proportions  by  the  different 
tissues,  according  to  the  quantity  necessary  for  their  organization. 
The  albuminous  ingredients  of  the  blood,  on  the  other  hand,  are 
not  only  absorbed  in  a  similar  manner  by  the  animal  tissues,  but  at 
the  same  time  are  transformed  by  catalysis,  and  converted  into  new 
materials,  characteristic  of  the  different  tissues.  In  this  way  are 
produced  the  musculine  of  the  muscles,  the  osteine  of  the  bones,  the 
cartilagine  of  the  cartilages,  &c.  &c.  It  is  probable  that  this  trans- 
formation does  not  take  place  in  the  interior  of  the  vessels  them- 
selves ;  but  that  the  organic  ingredients  of  the  blood  are  absorbed 
by  the  tissues,  and  at  the  same  moment  converted  into  new  mate- 
rials, by  contact  with  their  substance.  The  blood  in  this  way  fur- 
nishes, directly  or  indirectly,  all  the  materials  necessary  for  the 
nutrition  of  the  body. 

The  physical  conditions  which  influence  the  movement  of  the 
blood  in  the  capillaries,  are  somewhat  different  from  those  which 
regulate  the  arterial  and  venous  circulations.  We  must  remember 
that,  as  the  arteries  pass  from  the  heart  outward,  they  subdivide  and 
ramify  to  such  an  extent  that  the  surface  of  the  arterial  walls  is 
very  much  increased  in  proportion  to  the  quantity  of  blood  which 
they  contain.  It  is  on  this  account  that  the  arterial  pulsation  is  so 
much  equalized  at  a  distance  from  the  heart,  since  the  influence  of 
the  elasticity  of  the  arterial  coats  is  thus  constantly  increased  from 
within  outward.  But  as  these  vessels  finally  reach  the  confines 
of  the  arterial  system,  having  already  been  very  much  increased 
in  number  and  diminished  in  size,  they  suddenly  break  up  into 


THE    CAPILLARY    CIRCULATION.  299 

a  terminal  ramification  of  still  smaller  and  more  numerous  vessels, 
and  so  lose  themselves  at  last  in  the  capillary  network. 

Bj  this  final  increase  of  the  vascular  surface,  the  equalization  of 
the  heart's  action  is  completed.  There  is  no  longer  any  intermitting 
or  pulsatile  character  in  the  force  which  acts  upon  the  circulatino- 
fluid;  and  the  blood,  accordingly,  is  delivered  from  the  arteries  into 
the  capillaries  under  a  perfectly  continuous  and  uniform  pressure. 

This  pressure  is  sufficient  to  cause  the  blood  to  pass  with  con- 
siderable rapidity,  through  the  capillary  plexus,  into  the  commence- 
ment of  the  veins.  This  fact  was  first  demonstrated  by  Prof. 
Sharpey,'  of  London,  who  employed  an  injecting  syringe  with  a 
double  nozzle,  one  extremity  of  which  was  connected  with  a  mercu- 
rial gauge,  while  the  other  was  inserted  into  the  artery  of  a  recently 
killed  animal.  When  the  syringe,  filled  with  defibrinated  blood, 
was  fixed  in  this  position  and  the  vessels  of  the  animal  injected,  the 
defibrinated  blood  would  press  with  equal  force  upon  the  mercurv 
in  the  gauge  and  upon  the  fluid  in  the  bloodvessels ;  and  thus  it 
was  easy  to  ascertain  the  exact  amount  of  pressure  required  to  force 
the  defibrinated  blood  through  the  capillaries  of  the  animal,  and  to 
make  it  return  by  the  corresponding  vein.  In  this  way  Prof. 
Sharpey  found  that  when  the  free  end  of  the  injecting  tube  was 
attached  to  the  mesenteric  artery  of  the  dog,  a  pressure  of  90  milli- 
metres of  mercury  caused  the  blood  to  pass  through  the  capillaries 
of  the  intestine  and  of  the  liver ;  and  that  under  a  pressure  of  130 
millimetres,  it  flowed  in  a  full  stream  from  the  divided  extremity 
of  the  vena  cava. 

We  have  also  performed  a  similar  experiment  on  the  vessels  of 
the  lower  extremity.  A  full  grown  healthy  dog  was  killed,  and 
the  lower  extremity  immediately  injected  with  defibrinated  blood, 
by  the  femoral  artery,  in  order  to  prevent  coagulation  in  the  smaller 
vessels.  A  syringe  with  a  double  flexible  nozzle  was  then  filled 
with  defibrinated  blood,  and  one  extremity  of  its  injecting  tube 
attached  to  the  femoral  artery,  the  other  to  the  mouthpiece  of  a 
cardiometer.  By  making  the  injection,  it  was  then  found  that  the 
defibrinated  blood  ran  from  the  femoral  vein  in  a  continuous  stream 
under  a  pressure  of  120  millimetres,  and  that  it  was  discharged  very 
freely  under  a  pressure  of  130  millimetres. 

Since,  as  we  have  already  seen,  the  arterial  pressure  upon  the 

'  Todd  and  Bowmann,  Physiological  Anatomy  and  Physiology  of  man,  vol.  ii.  p. 
350. 


300  THE   CIRCULATION. 

blood  is  equal  to  six  inches,  or  150  millimetres,  of  mercury,  it  is 
evident  that  this  pressure  is  sufficient  to  propel  the  blood  through 
the  capillary  circulation. 

Beside,  the  blood  is  not  altogether  relieved  from  the  influence  of 
elasticity,  after  it  has  left  the  arteries.  For  the  capillaries  them- 
selves are  elastic,  notwithstanding  the  delicate  texture  of  their 
walls;  and  even  the  tissues  of  the  organs  which  they  traverse 
possess,  in  many  instances,  a  considerable  share  of  elasticity,  owing 
to  the  minute  elastic  fibres  which  are  scattered  through  their  sub- 
stance. These  elastic  fibres  are  found  in  considerable  quantity  in 
the  lungs,  the  spleen,  the  skin,  the  lobulated  glands,  and  more  or 
less  in  the  mucous  membranes.  They  are  abundant,  of  course,  in 
the  fibrous  tissues  of  the  extremities,  in  the  fasciae,  the  tendons,  and 
the  intermuscular  substance. 

In  the  experiment  of  injecting  the  vessels  of  the  lower  extremity 
with  defibrinated  blood,  if  the  injection  be  stopped,  the  blood  does 
not  instantly  cease  flowing  from  the  extremity  of  the  femoral  vein, 
but  continues  for  a  short  time,  until  the  elasticity  of  the  intervening 
parts  is  exhausted. 

The  same  thing  may  be  observed  even  in  the  liver.  If  the  end 
of  a  water-pipe  be  inserted  into  the  portal  vein,  and  the  liver  in- 
jected with  water  under  the  pressure  of  a  hydrant,  the  liquid  will 
distend  the  vessels  of  the  organ,  and  pass  out  by  the  hepatic  veins. 
But  if  the  portal  vein  be  suddenly  tied  or  compressed,  so  as  to  shut 
off  the  pressure  from  behind,  the  stream  will  continue  to  run,  for 
several  seconds  afterward,  from  the  hepatic  vein,  owing  to  the  re- 
action of  the  organ  itself  upon  the  fluid  contained  in  its  vessels. 

As  a  general  rule,  also,  the  capillaries  do  not  suffer  any  backward 
pressure  from  the  venous  system.  On  the  contrary,  as  soon  as  the 
blood  has  been  delivered  into  the  veins,  it  is  hurried  onward  toward 
the  heart  by  the  compression  of  the  muscles  and  the  action  of  the 
venous  valves.  The  right  side  of  the  heart  itself  continues  the  same 
process,  by  its  regular  contractions,  and  by  the  action  of  its  own 
valvular  apparatus ;  so  that  the  blood  is  constantly  lifted  away  from 
the  capillaries,  by  the  muscular  action  of  the  surrounding  parts. 

These  are  the  most  important  of  the  mechanical  influences  under 
which  the  blood  moves  through  the  continuous  round  of  the  circu- 
lation. The  heart,  by  its  alternating  contractions  and  relaxations, 
and  by  the  backward  play  of  its  valves,  continually  urges  the  blood 
forward  into  the  arterial  system.  The  arteries,  by  their  dilatable 
aad  elastic  walls,  convert  the  cardiac  pulsations  into  a  uniform  and 


THE    CAPILLARY    CIRCULATION'.  301 

steady  pressure.  Under  this  pressure,  the  blood  passes  through  the 
capillary  vessels;  and  it  is  then  carried  backward  to  the  heart 
through  the  veins,  assisted  by  the  action  of  the  muscles  and  the 
respiratory  movements  of  the  chest. 

At  the  same  time  there  are  certain  phenomena  which  are  very 
important  in  this  respect,  and  which  show  that  various  local  in- 
fluences will  either  excite  or  retard  the  capillary  circulation  in  par- 
ticular parts,  independently  of  the  heart's  action.  The  pallor  or 
suffusion  of  the  face  under  mental  emotion,  the  congestion  of  the 
mucous  membranes  during  the  digestive  process,  the  local  and  de- 
fined redness  produced  in  the  skin  by  an  irritating  application,  are 
all  instances  of  this  sort.  These  phenomena  are  usually  explained 
by  the  contraction  or  dilatation  of  the  smaller  arteries  immediately 
supplying  the  part  with  blood,  under  the  influence  of  nervous 
action.  As  we  know  that  the  smaller  arteries  are  in  fact  provided 
with  organic  muscular  fibres,  this  may  undoubtedly  have  something 
to  do  with  the  local  variations  of  the  capillary  circulation ;  but  the 
precise  manner  in  which  these  effects  are  produced  is  at  present 
unknown. 

The  rapidity  of  the  circulation  in  the  capillary  vessels  is  much 
less  than  in  the  arteries  or  the  veins.  It  may  be  measured,  with  a 
tolerable  approach  to  accuracy,  during  the  microscopic  examination 
of  transparent  and  vascular  tissues,  as,  for  example,  the  web  of  the 
frog's  foot,  or  the  mesentery  of  the  rat.  The  results  obtained  in 
this  way  by  different  observers  (Valentine,  "Weber,  Yolkmann,  &c.) 
show  that  the  rate  of  movement  of  the  blood  through  the  capil- 
laries is  rather  less  than  one-thirtieth  of  an  inch  per  second ;  or  not 
quite  two  inches  per  minute.  Since  the  rapidity  of  the  current,  as 
we  have  mentioned  above,  must  be  in  inverse  ratio  to  the  entire 
calibre  of  the  vessels  through  which  it  moves,  it  follows  that  the 
united  calibre  of  all  the  capillaries  of  the  body  must  be  from  350  to 
400  times  greater  than  that  of  the  arteries.  It  must  not  be  sup- 
posed from  this,  however,  that  the  whole  quantity  of  blood  contained 
in  the  capillaries  at  any  one  time  is  so  much  greater  than  that  in 
the  arteries;  since,  although  the  united  calibre  of  the  capillaries  is 
very  large,  their  length  is  very  small.  The  effect  of  the  anatomical 
structure  of  the  capillary  system  is,  therefore,  merely  to  disseminate 
a  comparatively  small  quantity  of  blood  over  a  very  large  space,  so 
that  the  chemico-physiological  reactions,  necessary  to  nutrition,  may 
take  place  with  promptitude  and  energy.  For  the  same  reason, 
although  the  rate  of  movement  of  the  blood  in  these  vessels  is  very 


302  THE    CIRCULATION. 

slow,  yet  as  tlie  distance  to  be  passed  over  between  tbe  arteries  and 
veins  is  very  small,  the  blood  really  requires  but  a  short  time  to 
traverse  the  capillary  system,  and  to  commence  its  returning  passage 
by  the  veins. 

GENERAL   CONSIDERATIONS. 

The  rapidity  with  which  the  blood  passes  through  the  entire  round 
of  the  circulation  is  a  point  of  great  interest,  and  one  which  has 
received  a  considerable  share  of  attention.  The  results  of  such 
experiments,  as  have  been  tried,  show  that  this  rapidity  is  much 
greater  than  would  have  been  anticipated.  Hering,  Poisseuille,  and 
Matteucci,^  have  all  experimented  on  this  subject  in  the  following 
manner.  A  solution  of  ferrocyanide  of  potassium  was  injected 
into  the  right  jugular  vein  of  a  horse,  at  the  same  time  that  a  liga- 
ture was  placed  upon  the  corresponding  vein  on  the  left  side,  and 
an  opening  made  in  it  above  the  ligature.  The  blood  flowing  from 
the  left  jugular  vein  was  then  received  in  separate  vessels,  which 
were  changed  every  five  seconds,  and  the  contents  afterward  exa- 
mined. It  was  thus  found  that  the  blood  drawn  from  the  first  to 
the  twentieth  second  contained  no  traces  of  the  ferrocyanide ;  but 
that  which  escaped  from  the  vein  at  the  end  of  from  twenty  to 
twenty-five  seconds,  showed  unmistakable  evidence  of  the  presence 
of  the  foreign  salt.  The  ferrocyanide  of  potassium  must,  therefore, 
during  this  time,  have  passed  from  the  point  of  injection  to  the 
right  side  of  the  heart,  thence  to  the  lungs  and  through  the  pulmo- 
nary circulation,  returned  to  the  heart,  passed  out  again  through 
the  arteries  to  the  capillary  system  of  the  head  and  neck,  and 
thence  have  commenced  its  returning  passage  to  the  right  side  of 
the  heart,  through  the  jugular  vein. 

By  extending  these  investigations  to  different  animals,  it  was 
found  that  the  duration  of  the  circulatory  movement  varied,  to 
some  extent,  with  the  size  and  species.  In  the  larger  quadrupeds, 
as  a  general  rule,  it  was  longer ;  in  the  smaller,  the  time  required 
was  less. 

In  the  Horse,^  the  mean  duration  was  28  seconds. 
"     Dog  "         "  "         "15         " 

"     Goat         "         "  "         «    13         " 

"     Fox  "         "  "         "    12J       " 

"     Rabbit     "        "  "         "      7        " 


'  Physical  Phenomena  of  Living  Beings,  Pereira's  translation,  Philada.  ed.,  1848, 
p.  317. 

2  In  Milne  Edwards,  Le9ons  sur  la  Physiologie,  &c.,  voL  iv.  p.  364. 


LOCAL    VARIATIONS.  303 

"When  these  results  were  first  published,  it  was  thought  to  be 
doubtful  whether  the  circulation  were  really  as  rapid  as  they  would 
make  it  appear.  It  was  thought  that  the  saline  matter  which  was 
injected,  "  travelled  faster  than  the  blood ;"  that  it  became  "  diffused" 
throuojh  the  circulating  fluid;  that  it  transuded  through  dividino^ 
membranes ;  or  passed  round  to  the  point  at  which  it  was  detected, 
by  some  short  and  irregular  route. 

But  none  of  these  explanations  have  ever  been  found  to  be  cor- 
rect. They  are  all  really  more  improbable  than  the  fact  which 
they  are  intended  to  explain.  The  physical  diffusion  of  liquids 
does  not  take  place  with  such  rapidity  as  that  manifested  by  the 
circulation ;  and  there  is  no  other  route  so  likely  to  give  passage  to 
the  injected  fluid,  as  the  bloodvessels  and  the  movement  of  the  blood 
itself.  Beside,  the  first  experiments  of  Poisseuille  and  others  have 
not  been  since  invalidated,  in  any  essential  particular.  It  was  found, 
it  is  true,  that  certain  other  substances,  injected  at  the  same  time 
with  the  saline  matter,  might  hasten  or  retard  the  circulation  to  a 
certain  degree.  But  these  variations  were  not  very  marked,  and 
never  exceeded  the  limits  of  from  eighteen  to  forty-five  seconds. 
There  is  no  doubt  that  the  blood  itself  makes  the  same  circuit  in 
very  nearly  the  same  interval  of  time. 

The  truth  is,  however,  that  we  cannot  fix  upon  any  absolutely 
uniform  rate  which  shall  express  the  time  required  by  the  entire 
blood  to  pass  the  round  of  the  whole  vascular  system,  and  return 
to  a  given  point.  The  circulation  of  the  blood,  far  from  being  a 
simple  phenomenon,  like  a  current  of  water  through  a  circular  tube, 
is,  on  the  contrary,  extremely  complicated  in  all  its  anatomical  and 
physiological  conditions ;  and  it  differs  in  rapidity,  as  well  as  in  its 
physical  and  chemical  phenomena,  in  different  parts  of  the  circu- 
latory apparatus.  We  have  already  seen  how  much  the  form  of 
the  capillary  plexus  varies  in  different  organs.  In  some  the  vascu- 
lar network  is  close,  in  others  comparatively  open.  In  some  its 
meshes  are  circular  in  shape,  in  others  polygonal,  in  others  rectan- 
gular. In  some  the  vessels  are  arranged  in  twisted  loops,  in  others 
they  communicate  by  irregular  but  abundant  inosculations.  The 
mere  distance  from  the  heart  at  which  an  organ  is  situated  must 
modify  to  some  extent  the  time  required  for  its  blood  to  return 
again  to  the  centre  of  the  circulation.  The  blood  which  passes 
through  the  coronary  arteries  and  the  capillaries  of  the  heart, 
for  example,  must  be  returned  to  the  right  auricle  in  a  compara- 
tively short  time ;  while  that  which  is  carried  by  the  carotids  into 


80J:  THE    CIRCULATION. 

the  capillary  sj^stem  of  the  head  and  neck,  to  return  by  the  jugulars, 
will  require  a  longer  interval.  That,  again,  which  descends  by  the 
abdominal  aorta  and  its  divisions  to  the  lower  extremities,  and 
which,  after  circulating  through  the  tissues  of  the  leg  and  foot, 
mounts  upward  through  the  whole  course  of  the  saphena,  femoral, 
iliac  and  abdominal  veins,  must  be  still  longer  on  its  way ;  while 
that  which  circulates  through  the  abdominal  digestive  organs  and 
is  then  collected  by  the  portal  system,  to  be  again  dispersed  through 
the  glandular  tissue  of  the  liver,  requires  undoubtedly  a  longer 
period  still  to  perform  its  double  capillary  circulation.  The  blood, 
therefore,  arrives  at  the  right  side  of  the  heart,  from  different  parts 
of  the  body,  at  successive  intervals;  and  may  pass  several  times 
through  one  organ  while  performing  a  single  circulation  through 
another. 

Furthermore,  the  chemical  phenomena  taking  place  in  the  blood 
and  the  tissues  vary  to  a  similar  extent  in  different  organs.  The 
actions  of  transformation  and  decomposition,  of  nutrition  and  secre- 
tion, of  endosmosis  and  exosmosis,  which  go  on  simultaneously 
throughout  the  body,  are  yet  extremely  varied  in  their  character, 
and  produce  a  similar  variation  in  the  phenomena  of  the  circula- 
tion. In  one  organ  the  blood  loses  more  fluid  than  it  absorbs  ;  in 
another  it  absorbs  more  than  it  loses.  The  venous  blood,  conse- 
quently, has  a  diflerent  composition  as  it  returns  from  different 
organs.  In  the  b]'ain  and  spinal  cord  it  gives  up  those  ingredients 
necessary  for  the  nutrition  of  the  nervous  matter,  and  absorbs  cho- 
lesterine  and  other  materials  resulting  from  its  waste ;  in  the  muscles 
it  loses  those  substances  necessary  for  the  supply  of  the  muscular 
tissue,  and  in  the  bones  those  which  are  requisite  for  the  osseous 
system.  In  the  parotid  gland  it  yields  the  ingredients  of  the  saliva ; 
in  the  kidneys,  those  of  the  urine.  In  the  intestine  it  absorbs  in 
large  quantity  the  nutritious  elements  of  the  digested  food ;  and  in 
the  liver,  gives  up  substances  destined  finally  to  produce  the  bile, 
at  the  same  time  that  it  absorbs  sugar,  which  has  been  produced 
in  the  hepatic  tissue.  In  the  lungs,  again,  it  is  the  elimination  of 
carbonic  acid  and  the  absorption  of  oxygen  that  constitute  its  prin- 
cipal changes.  It  has  been  already  remarked  that  the  temperature 
of  the  blood  varies  in  different  veins,  according  to  the  peculiar 
chemical  and  nutritive  changes  going  on  in  the  organs  from  which 
they  originate.  Its  color,  even,  which  is  also  dependent  on  the 
chemical  and  nutritive  actions  taking  place  in  the  capillaries,  varies 
in  a  similar  manner.     In  the  lungs  it  changes  from  blue  to  red ; 


LOCAL    VARIATIONS. 


305 


Fig.  101. 


in  the  capillaries  of  the  general  system,  from  red  to  blue.     But  its 

tinge  also  varies  very  considerably  in  different  parts  of  the  general 

circulation.    The  blood  of  the  hepatic 

veins  is  darker  than  that  of  the  femoral 

"or  brachial  vein.     In  the  renal  veins 

it  is  very  much  brighter  than  in  the 

vena  cava ;  and  when  the  circulation 

through  the  kidneys  is  free,  the  blood 

returning  from  them  is  nearly  as  red 

as  arterial  blood. 

We  must  regard  the  circulation  of 
the  blood,  therefore,  not  as  a  simple 
process,  but  as  made  up  of  many  differ- 
ent circulations,  going  on  simultane- 
ously in  different  organs.  It  has  been 
customary  to  illustrate  it,  in  diagram, 
by  a  double  circle,  or  figure  of  8,  of 
which  the  upper  arc  is  used  to  repre- 
sent the  pulmonary,  the  lower  the  gen- 
eral circulation.  This,  however,  gives 
but  a  very  imperfect  idea  of  the  entire 
circulation,  as  it  really  takes  place.  It 
would  be  much  more  accurately  re- 
presented by  such  a  diagram  as  that 
in  Fig.  101,  in  which  its  variations 
in  different  parts  of  the  body  are 
indicated  in  such  a  manner  as  to  show, 
in  some  degree,  the  complicated  cha- 
racter of  its  phenomena.  The  circula- 
tion is  modified  in  these  different  parts, 
not  only  in  its  mechanism,  but  also  in 
its  rapidity  and  quantity,  and  in  the 
nutritive  functions  performed  by  the 
blood.  In  one  part,  it  stimulates  the 
nervous  centres  and  the  organs  of 
special  sense ;  in  others  it  supplies  the 
fluid  secretions,  or  the  ingredients  of 
the  solid  tissues.  One  portion,  in 
passing  through  the  digestive  appara- 
tus, absorbs   the  materials   requisite 

for  the  nourishment  of  the  body ;  another,  in  circulating  through 
20 


Diagram  of  tlie  Circ0lation.  —  !• 
Heart.  2.  Lungs.  3.  Head  and  upper 
extremities.  4.  Spleen.  5.  Intestine.  6. 
Kidney.    7.  Lower  cxti-emities.     8.  Liver. 


306  THE    CIKCULATION. 

the  lungs,  exhales  the  carbonic  acid  which  it  has  accumulated  else- 
where, and  absorbs  the  oxygen  which  is  afterward  transported  to 
distant  tissues  by  the  curl-ent  of  arterial  blood.  The  phenomena  of 
the  circulation  are  even  liable,  as  we  have  already  seen,  to  periodical 
variations  in  the  same  organ ;  increasing  or  diminishing  in  intensity 
with  the  condition  of  rest  or  activity  of  the  whole  body,  or  of  the 
particular  organ  which  is  the  subject  of  observation. 


IMBIBITION    AND    EXHALATION.  307 


CHAPTER   XV. 

IMBIBITION  AND  EX  HAL  ATI  ON.— THE  LYMPHATIC 

SYSTEM. 

During  the  passage  of  the  blood  througli  the  capillaries  of  the 
circulatory  system,  a  very  important  series  of  changes  takes  place 
by  which  its  ingredients  are  partly  transferred  to  the  tissues  by 
exhalation,  and  at  the  same  time  replaced  by  others  which  the  blood 
derives  by  absorption  from  the  adjacent  parts.  These  phenomena 
depend  upon  the  property,  belonging  to  animal  membranes,  of 
imbibing  or  absorbing  certain  fluid  substances  in  a  peculiar  way. 
They  are  known  more  particularly  as  the  phenomena  of  endosmosis 
and  exosmosis. 

These  phenomena  may  be  demonstrated  in  the  following  way.  If 
we  take  two  different  liquids,  for  example  a  solution  of  salt  and  an 
equal  quantity  of  distilled  water,  and  inclose  them  in  a  glass  vessel 
with  a  fresh  animal  membrane  stretched  between,  so  that  there  is 
no  direct  communication  from  one  to  the  other,  the  two  liquids 
being  in  contact  with  opposite  sides  of  the  membrane,  it  will  be 
found  after  a  time  that  the  liquids  have  become  mixed,  to  a  cer- 
tain extent,  with  each  other.  A  part  of  the  salt  will  have  passed 
into  the  distilled  water,  giving  it  a  saline  taste ;  and  .a  part  of  the 
water  will  have  passed  into  the  saline  solution,  making  it  more 
dilute  than  before.  If  the  quantities  of  the  two  liquids,  which 
have  become  so  transferred,  be  measured,  it  will  be  found  that  a 
comparatively  large  quantity  of  the  water  has  passed  into  the 
saline  solution,  and  a  comparatively  small  quantity  of  the  saline 
solution  has  passed  out  into  the  water.  That  is,  the  water  passes 
inward  to  the  salt  more  rapidly  than  the  salt  passes  outward  to  the 
water.  The  consequence  is,  that  an  accumulation  soon  begins  to 
show  itself  on  the  side  of  the  salt.  The  saline  solution  is  increased 
in  volume  and  diluted,  while  the  water  is  diminished  in  volume, 
and  acquires  a  saline  ingredient.  This  abundant  passage  of  the 
water,  through  the  membrane,  to  the  salt,  is  called  endosmosis ;  and 


308  IMBIBITION    AND    EXHALATION. 

the  more  scanty  passage  of  the  salt  outward  to  the  water  is  called 
exosmosis. 

The  mode  usually  adopted  for  measuring  the  rapidity  of  endos- 
mosis  is  to  take  a  glass  vessel,  shaped  somewhat  like  an  inverted 
funnel,  wide  at  the  bottom  and  narrow  at  the  top.  The  bottom  of 
the  vessel  is  closed  by  a  thin  animal  membrane,  like  the  mucous 
membrane  of  an  ox-bladder,  which  is  stretched  tightly  over  its  edge 
and  secured  by  a  ligature.  From  the  top  of  the  vessel  there  rises 
a  very  narrow  glass  tube,  open  at  its  upper  extremity.  "When  the 
instrument  is  thus  prepared,  it  is  filled  with  a  solution  of  sugar 
and  placed  in  a  vessel  of  distilled  water,  so  that  the  animal  mem- 
brane, stretched  across  its  mouth,  shall  be  in  contact  with  pure 
water  on  one  side  and  with  the  saccharine  solution  on  the  other. 
The  water  then  passes  in  through  the  membrane,  by  endosmosis, 
faster  than  the  saccharine  solution  passes  out.  An  accumulation 
therefore  takes  place  inside  the  vessel,  and  the  level  of  the  fluid 
rises  in  the  upright  tube.  The  height  to  which  the  fluid  thus  rises 
in  a  given  time  is  a  measure  of  the  intensity  of  the  endosmosis,  and 
of  its  excess  over  exosmosis.  By  varying  the  constitution  of  the 
two  liquids,  the  arrangement  of  the  membrane,  &c.,  the  variation 
in  endosmotio  action  under  different  conditions  may  be  easily 
ascertained.     Such  an  instrument  is  called  an  endosmometer. 

If  the  extremity  of  the  upright  tube  be  bent  over,  so  as  to  point 
downward,  as  endosmosis  continues  to  go  on  after  the  tube  has 
become  entirely  filled  by  the  rising  of  the  fluid,  the  saccharine  solu- 
tion will  be  discharged  in  drops  from  the  end  of  the  tube,  and  fall 
back  into  the  vase  of  water.  A  steady  circulation  will  thus  be 
kept  up  for  a  time  by  the  force  of  endosmosis.  The  water  still 
passes  through  the  membrane,  and  accumulates  in  the  endosmo- 
meter ;  but,  as  this  is  already  full  of  fluid,  the  surplus  immediately 
falls  back  into  the  outside  vase,  and  thus  a  current  is  established 
which  will  go  on  until  the  two  liquids  have  become  intimately 
mingled. 

The  conditions  which  influence  the  rapidity  and  extent  of  endos- 
mosis have  been  most  thoroughly  investigated  by  Dutrochet,  who 
was  the  first  to  make  a  systematic  examination  of  the  subject. 

The  first  of  these  conditions  is  the  freshness  of  the  membrane  itself. 
This  is  an  indispensable  requisite  for  the  success  of  the  experiment. 
A  membrane  that  has  been  dried  and  moistened  again,  or  one  that 
has  begun  to  putrefy,  will  not  produce  the  desired  effect.  It  has 
been  also  found  that  if  the  membrane  of  the  endosmometer  be 


THE    LYMPHATIC    SYSTEM.  309 

allowed  to  remain  and  soak  in  the  fluids,  after  the  column  has  risen 
to  a  certain  height  in  the  upright  tube,  it  begins  to  descend  again 
as  soon  as  putrefaction  commences,  and  the  two  liquids  finally  sink 
to  the  same  level. 

The  next  condition  is  the  extent  of  contact  between  the  membrane 
and  the  two  liquids.  The  greater  the  extent  of  this  contact,  the 
more  rapid  and  forcible  is  the  current  of  endosmosis.  An  endos- 
mometer  with  a  wide  mouth  will  produce  more  effect  than  with  a 
narrow  one,  though  the  volume  of  the  liquid  contained  in  it  may 
be  the  same  in  both  instances.  The  action  takes  place  at  the 
surface  of  the  membrane,  and  is  proportionate  to  its  extent. 

Another  very  important  circumstance  is  the  constitution  of  the  two 
liquids,  and  their  relation  to  each  other.  As  a  general  thing,  if  we 
use  water  and  a  saline  solution  in  our  experiments,  endosmosis  is 
more  active,  the  more  concentrated  is  the  solution  in  the  endosmo- 
meter.  A  larger  quantity  of  water  will  pass  inward  toward  a  dense 
solution  than  toward  one  which  is  already  dilute.  But  the  force  of 
endosmosis  varies  with  different  liquids,  even  when  they  are  of  the 
same  density.  Dutrochet  measured  the  force  with  which  water 
passed  through  the  mucous  membrane  of  an  ox-bladder  into  differ- 
ent solutions  of  the  same  density.  He  found  that  the  force  varies 
with  different  substances,  as  follows  •} — 


Endosmosis  of  water,  with  a  solution  of  albumen 


12 

11 

5 

3 


sugar      . 
"  "  "  gum 

"  "  "  gelatine 

The  position  of  the  membrane  also  makes  a  difference.  With  some 
fluids,  endosmosis  is  more  rapid  when  the  membrane  has  its  mucous 
surface  in  contact  with  the  dense  solution,  and  its  dissected  surface 
in  contact  with  the  water.  With  other  substances  the  more  favor- 
able position  is  the  reverse.  Matteucci  found  that,  in  using  the 
mucous  membrane  of  the  ox-bladder  with  water  and  a  solution  of 
sugar,  if  the  mucous  surface  of  the  membrane  were  in  contact  with 
the  saccharine  solution,  the  liquid  rose  in  the  endosmometer  between 
four  and  five  inches.  But  if  the  same  surface  were  turned  outward 
toward  the  water,  the  column  of  fluid  was  less  than  three  inches  in 
height.  Different  membranes  also  act  with  different  degrees  of  force. 
The  effect  produced  is  not  the  same  with  the  integument  of  different 
animals,  nor  with  mucous  membranes  taken  from  different  parts  of 
the  body. 

'  In  M-'ittPunci's  Lectures  on  the  Physical  Phenomena  of  Living  Beings.    Philada., 
1848,  p.  48. 


310  IMBIBITION    AND    EXHALATION. 

Generally  speaking,  endosmosis  is  more  active  when  the  temi^er- 
ature  is  moderately  elevated.  Dutrochet  noticed  that  an  endosmo- 
meter,  containing  a  solution  of  gum,  absorbed  only  one  volume  of 
water  at  a  temperature  of  32°  Fahr.,  but  absorbed  three  volumes 
at  a  temperature  a  little  above  90°.  Variations  of  temperature  will 
sometimes  even  change  the  direction  of  the  endosmosis  altogether, 
particularly  with  dilute  solutions  of  hydrochloric  acid.  Dutrochet 
found,  for  example,^  that  when  the  endosmometer  was  filled  with 
dilute  hydrochloric  acid  and  placed  in  distilled  water,  at  the  tem- 
perature of  50°  F.,  endosmosis  took  place  from  the  acid  to  the  water, 
if  the  density  of  the  acid  solution  were  less  than  1.020 ;  but  that  it 
took  place  from  the  water  to  the  acid,  if  its  density  were  greater 
than  this.  On  the  other  hand,  at  the  temperature  of  72°  F.,  the 
current  was  from  within  outward  when  the  density  of  the  acid  solu- 
tion was  below  1.003,  and  from  without  inward  when  it  was  above 
that  point. 

Finally,  the  pressure  which  is  exerted  upon  the  fluids  and  the 
membrane  favors  their  endosmosis.  Fluids  that  pass  slowly  under 
a  low  pressure  will  pass  more  rapidly  with  a  higher  one.  Different 
liquids,  too,  require  different  degrees  of  pressure  to  make  them 
pass  the  same  membrane.  Liebig"^  has  measured  the  pressure  re- 
quired for  several  different  liquids,  in  order  to  make  them  pass 
through  the  same  membrane.     He  found  that  this  pressure  was 

Inches  of  Mekcury. 
For  alcohol         ........         52 

For  oil 37 

For  solution  of  salt 20 

For  water 13 

There  are  some  cases  in  which  endosmosis  takes  place  without 
being  accompanied  by  exosmosis.  This  occurs,  for  example,  when 
we  use  water  and  albumen  as  the  two  liquids.  For  while  water 
readily  passes  in  through  the  animal  membrane,  the  albumen  does 
not  pass  out.  If  an  opening  be  made,  for  example,  in  the  large 
end  of  an  egg,  so  as  to  expose  the  shell-membrane,  and  the  whole 
be  then  placed  in  a  goblet  of  water,  endosmosis  will  take  place  very 
freely  from  the  water  to  the  albumen,  so  as  to  distend  the  shell- 
membrane  and  make  it  protrude,  like  a  hernia,  from  the  opening  in 
the  shell.  But  the  albumen  does  not  pass  outward  through  the 
membrane,  and  the  water  in  the  goblet  remains  pure.    After  a  time, 

'  In  Milne  Edwards,  Lemons  sur  la  Physiologie,  &o.,  vol.  v.  p.  164. 
^  In  Longet's  Traite  de  Physiologie,  vol.  i.  p.  384. 


THE    LYMPHATIC    SYSTEM.  311 

however,  the  accumulation  of  fluid  in  the  interior  becomes  so  ex. 
cessive  as  to  burst  the  shell- membrane,  and  then  the  two  liquids 
become  mixed  indiscriminately  together. 

These  are  the  principal  conditions  bj  which  endosmosis  is  influ. 
enced  and  regulated.  Let  us  now  see  what  is  the  nature  of  the 
process,  and  upon  what  its  phenomena  depend. 

Endosmosis  is  not  dependent  upon  the  simple  force  of  diffusion 
or  admixture  of  two  different  liquids.  For  sometimes,  as  in  the 
case  of  albumen  and  water,  all  the  fluid  passes  in  one  direction  and 
none  in  the  other.  It  is  true  that  the  activity  of  the  process  de- 
pends very  much,  as  we  have  already  seen,  upon  the  difference  in 
constitution  of  the  two  liquids.  "With  water  and  a  saline  solution, 
for  instance,  the  stronger  the  solution  of  salt,  the  more  rapid  is  the 
endosmosis  of  the  water.  And  if  two  solutions  of  salt  be  used, 
with  a  membranous  septum  between  them,  endosmosis  takes  place 
from  the  weaker  solution  to  the  stronger,  and  is  proportionate  in 
activity  to  the  difference  in  their  densities.  From  this  fact,  Dutro- 
chet  was  at  first  led  to  believe  that  the  direction  of  endosmosis  was 
determined  by  the  difference  in  density  of  the  two  liquids,  and  that 
the  current  of  accumulation  was  always  directed  from  the  lighter 
liquid  to  the  denser.  But  we  now  know  that  this  is  not  the  case. 
For  though,  with  solutions  of  salt,  sugar,  and  the  like,  the  current 
of  endosmosis  is  from  the  lighter  to  the  denser  liquid ;  in  other 
instances  it  is  the  reverse.  With  water  and  alcohol,  for  example, 
endosmosis  takes  place,  not  from  the  alcohol  to  the  water,  but  from 
the  water  to  the  alcohol ;  that  is,  from  the  denser  liquid  to  the  lighter. 
The  difference  in  density  of  the  liquids,  therefore,  is  not  the  only 
condition  which  regulates  the  direction  of  the  endosmotic  current. 
In  point  of  fact,  the  process  of  endosmosis  does  not  depend  princi- 
pally upon  the  attraction  of  the  two  liquids  for  each  other,  but 
upon  the  attraction  of  the  animal  membrane  for  the  two  liquids.  The 
membrane  is  not  a  passive  filter  through  which  the  liquids  mingle, 
but  it  is  the  active  agent  which  determines  their  passage.  The 
membrane  has  the  power  of  absorbing  liquids,  and  of  taking  them 
up  into  its  own  substance.  This  power  of  absorption,  belonging  to 
the  membrane,  depends  upon  the  organic  or  albuminous  ingredients 
of  which  it  is  composed ;  and,  with  different  animal  substances,  the 
power  of  absorption  is  different.  The  tissue  of  cartilage,  for  exam- 
ple, will  absorb  more  water,  weight  for  weight,  than  that  of  the 
tendons ;  and  the  tissue  of  the  cornea  will  absorb  nearly  twice  as 
much  as  that  of  cartilagre. 


812  IMBIBITION'    AND    EXHALATION. 

Beside,  the  power  of  absorption  of  an  animal  membrane  is  dif- 
ferent for  different  liquids.  Nearly  all  animal  membranes  absorb 
pure  water  more  freely  than  a  solution  of  salt.  If  a  membrane, 
partly  dried,  be  placed  in  a  saturated  saline  solution,  it  will  absorb 
the  water  in  larger  proportion  than  the  salt,  and  a  part  of  the  salt 
will,  therefore,  be  deposited  in  the  form  of  crystals  on  the  surface 
of  the  membrane. 

Oily  matters,  on  the  other  hand,  are  usually  absorbed  less  readily 
than  either  water  or  saline  solutions, 

Chevreuil  has  investigated  the  absorbent  power  of  different 
animal  substances  for  different  liquids,  by  taking  definite  quanti- 
ties of  the  animal  substance  and  immersing  it  for  twenty-four 
hours  in  different  liquids.  At  the  end  of  that  time,  the  substance 
was  removed  and  weighed.  Its  increase  in  weight  showed  the 
quantity  of  liquid  which  it  had  absorbed.  The  results  which  were 
obtained  are  given  in  the  following  table : — * 


100  Pakts  of 

Water. 

Sa 

LINE  Solution. 

Oil. 

Cartilage, 

f  231 

parts. 

125  parts. 

Tendon, 

178 

114     " 

8.6  parts 

Elastic  ligament, 

absorb  in   ,    148 

30     " 

7.2     " 

Cornea, 

"  24  hours,  ' 

461 

370     " 

9.1     " 

Cartilaginous  ligament, 

319 

3.2     " 

Dried  fibrin, 

-  301 

154     " 

The  same  substance,  therefore,  will  take  np  different  quantities 
of  water,  saline  solutions,  and  oil. 

Accordingly,  when  an  animal  membrane  is  placed  in  contact 
with  two  different  liquids,  it  absorbs  one  of  them  more  abundantly 
than  the  other ;  and  that  which  is  absorbed  in  the  greatest  quantity 
is  also  diffused  most  abundantly  into  the  liquid  on  the  opposite  side 
of  the  membrane.  A  rapid  endosmosis  takes  place  in  one  direc- 
tion, and  a  slow  exosmosis  in  the  other.  Consequently,  the  least 
absorbable  fluid  increases  in  volume  by  the  constant  admixture  of 
that  which  is  taken  up  more  rapidly. 

The  process  of  endosmosis,  therefore,  is  essentially  one  of  im- 
bibition or  absorption  of  the  liquid  by  an  animal  membrane,  com- 
posed of  organic  ingredients.  We  have  already  shown,  in  de- 
scribing the  organic  proximate  principles  in  a  previous  chapter, 
that  these  substances  have  the  power  of  absorbing  watery  and 
serous  fluids  in  a  peculiar  way.    In  endosmosis,  accordingly,  the 

•  In  Longet's  Traite  de  Physiologie,  vol.  i.  p.  383. 


THE    LYMPHATIC    SYSTEM.  313 

imbibed  fluid  penetrates  the  membrane  by  a  kind  of  cbemical 
combination,  and  unites  intimately  with,  the  substance  of  which,  its 
tissues  are  composed. 

It  is  in  this  way  that  all  imbibition  and  transudation  take  place 
in  the  living  body.  Under  the  most  ordinary  conditions,  the  transu- 
dation of  certain  fluids  is  accomplished  with  great  rapidity.  It  has 
been  shown  by  M.  Gosselin,^  that  if  a  watery  solution  of  iodide  of 
potassium  be  dropped  upon  the  cornea  of  a  living  rabbit,  the 
iodine  passes  into  the  cornea,  aqueous  humor,  iris,  lens,  sclerotic 
and  vitreous  body,  in  the  course  of  eleven  minutes ;  and  that  it 
will  penetrate  through  the  cornea  into  the  aqueous  humor  in  three 
minutes,  and  into  the  substance  of  the  cornea  in  a  minute  and  a 
half.  In  these  experiments  it  was  evident  that  the  iodine  actually 
passed  into  the  deeper  portions  of  the  eye  by  simple  endosmosis, 
and  was  not  transported  by  the  vessels  of  the  general  circulation ; 
since  no  trace  of  it  could  be  found  in  the  tissues  of  the  opposite 
eye,  examined  at  the  same  time. 

The  same  observer  showed  that  the  active  principle  of  belladonna 
penetrates  the  tissues  of  the  eyeball  in  a  similar  manner.  M.  Gos- 
selin  applied  a  solution  of  sulphate  of  atropine  to  both  eyes  of  two 
rabbits.  Half  an  hour  afterward,  the  pupils  were  dilated.  Three 
quarters  of  an  hour  later,  the  aqueous  humor  was  collected  by 
puncturing  the  cornea  with,  a  trocar;  and  this  aqueous  humor, 
dropped  upon  the  eye  of  a  cat,  produced  dilatation  and  immobility 
of  the  pupil  in  half  an  hour.  These  facts  show  that  the  aqueous 
bumor  of  the  affected  eye  actually  contains  atropine,  which  it 
absorbs  from  without  through  the  corijea,  and  this  atropine  then 
acts  directly  and  locally  upon  the  muscular  fibres  of  the  iris. 

But  in  all  the  vascular  organs,  the  processes  of  endosmosis  and 
exosmosis  are  very  much  accelerated  by  two  important  conditions, 
viz.,  first,  the  movement  of  the  blood  in  circulating  through  the 
vessels,  and  secondly  the  minute  dissemination  and  distribution  of 
these  vessels  through  the  tissue  of  the  organs. 

The  movement  of  a  fluid  in  a  continuous  current  always  favors 
endosmosis  through  the  membrane  with  which  it  is  in  contact.  For 
if  the  two  liquids  be  stationary,  on  the  opposite  sides  of  an  animal 
membrane,  as  soon  as  endosmosis  commences  they  begm  to  ap- 
proximate in  constitution  to  each  other  by  mutual  admiixture ;  and, 
as  this  admixture  goes  on,  endosmosis  of  course  becomes  less  active, 

'  Gazette  Hebdomadaire,  Sept.  7,  1855. 


314  IMBIBITION    AND    EXHALATION. 

and  ceases  entirely  when  the  two  liquids  have  become  perfectly- 
alike  in  composition.  But  if  one  of  the  liquids  be  constantly 
renewed  by  a  continuous  current,  those  portions  of  it  which  have 
become  contaminated  are  immediately  carried  away  by  the  stream, 
and  replaced  by  fresh  portions  in  a  state  of  purity.  Thus  the 
difference  in  constitution  of  the  two  liquids  is  preserved,  and 
transudation  will  continue  to  take  place  between  them  with  una- 
bated rapidity. 

Matteucci  demonstrated  the  effect  of  a  current  in  facilitating 
endosmosis  by  attaching  to  the  stopcock  of  a  glass  reservoir  filled 
with  water,  a  portion  of  a  vein  also  filled  with  water.  The  vein 
was  then  immersed  in  a  very  dilute  solution  of  hydrochloric  acid. 
So  long  as  the  water  remained  stationary  in  the  vein  it  did  not  give 
any  indications  of  the  presence  of  the  acid,  or  did  so  only  very 
slowly ;  but  if  a  current  were  allowed  to  pass  through  the  vein  by 
opening  the  stopcock  of  the  reservoir,  then  the  fluid  running  from 
its  extremity  almost  immediately  showed  an  acid  reaction. 

The  same  thing  may  be  shown  even  more  distinctly  upon  the 
living  animal.  If  a  solution  of  the  extract  of  nux  vomica  be  in- 
jected into  the  subcutaneous  areolar  tissue  of  the  hind  leg  of  two 
rabbits,  in  one  of  which  the  bloodvessels  of  the  extremity  have 
been  left  free,  while  in  the  other  they  have  been  previously  tied, 
so  as  to  stop  the  circulation  in  that  part — in  the  first  rabbit,  the 
poison  will  be  absorbed  and  will  produce  convulsions  and  death  in 
the  course  of  a  few  minutes;  but  in  the  second  animal,  owing  to  the 
stoppage  of  the  local  circulation,  absorption  will  be  much  retarded, 
and  the  poison  will  find  its  way  into  the  general  circulation  so 
slowly,  and  in  such  small  quantities,  that  its  specific  effects  will  show 
themselves  only  at  a  late  period,  or  even  may  not  be  produced  at  all. 

The  anatomical  arrangement  of  the  bloodvessels  and  adjacent 
tissues  is  the  second  important  condition  regulating  endosmosis 
and  exosmosis.  "We  have  already  seen  that  the  network  of  capil- 
lary bloodvessels  results  from  the  excessive  division  and  ramifica- 
tion of  the  smaller  arteries.  The  blood,  therefore,  as  it  leaves  the 
arteries  and  enters  the  capillaries,  is  constantly  divided  into  smaller 
and  more  numerous  currents,  which  are  finally  disseminated  in  the 
most  intricate  manner  throughout  the  substance  of  the  organs  and 
tissues.  Thus,  the  blood  is  brought  into  intimate  contact  with  the 
surrounding  tissues,  over  a  comparatively  very  large  extent  of  sur- 
face. It  has  already  been  stated,  as  the  result  of  Dutrochet's  inves- 
tigations, that  the  activity  of  endosmosis  is  in  direct  proportion  to 


THE    LYMPHATIC    SYSTEM.  815 

the  extent  of  surface  over  which  the  two  liquids  come  in  contact 
with  the  intervening  membrane.     It  is  very  evident,  therefore,  that 
it  will  be  very  much  facilitated  by  the  anatomical  distribution  of 
■  the  capillary  bloodvessels. 

It  is  in  some  of  the  glandular  organs,  however,  that  the  transu- 
dation of  fluids  can  be  shown  to  take  place  with  the  greatest  rapi- 
dity. For  in  these  organs  the  exhaling  and  absorbing  surfaces  are 
arranged  in  the  form  of  minute  ramifying  tubes  and  follicles,  which 
penetrate  everywhere  through  the  glandular  substance ;  while  the 
capillary  bloodvessels  form  an  equally  complicated  and  abundant 
network,  situated  between  the  adjacent  follicles  and  ducts.  In  this 
way,  the  union  and  interlacement  of  the  glandular  membrane,  on 
the  one.  hand,  and  the  bloodvessels  on  the  other,  become  exceed- 
ingly intricate  and  extensive ;  and  the  ingredients  of  the  blood  are 
almost  instantaneously  subjected,  over  a  very  large  surface,  to  the 
influence  of  the  glandular  membrane. 

The  rapidity  of  transudation  through  the  glandular  membranes 
has  been  shown  in  a  very  striking  manner  by  Bernard."  This  ob- 
server injected  a  solution  of  iodide  of  potassium  into  the  duct  of 
the  parotid  gland  on  the  right  side,  in  a  living  dog,  and  immediately 
afterward  found  iodine  to  be  present  in  the  saliva  of  the  correspond- 
ing gland  on  the  opposite  side.  In  the  few  instants,  therefore,  re- 
quired to  perform  the  experiment,  the  salt  of  iodine  must  have 
been  taken  up  by  the  glandular  tissue  on  one  side,  carried  by  the 
blood  of  the  general  circulation  to  the  opposite  gland,  and  there 
transuded  through  the  secreting  membrane. 

We  have  also  found  the  transudation  of  iodine  through  the 
glandular  tissue  to  be  exceedingly  rapid,  by  the  following  experi- 
ment. The  parotid  duct  was  exposed  and  opened,  upon  one  side, 
in  a  living  dog,  and  a  canula  inserted  into  it,  and  secured  by  liga- 
ture. The  secretion  of  the  parotid  saliva  was  then  excited,  by  in- 
ti-oducing  a  little  vinegar  into  the  mouth  of  the  animal,  and  the 
saliva,  thus  obtained,  found  to  be  entirely  destitute  of  iodine.  A 
solution  of  iodide  of  potassium  being  then  injected  into  the  jugu- 
lar vein,  and  the  parotid  secretion  again  immediately  excited  by 
the  introduction  of  vinegar,  as  before,  the  saliva  first  discharged 
from  the  canula  showed  evident  traces  of  iodine,  by  striking  a  blue 
color  on  the  addition  of  starch  and  nitric  acid. 

The  processes  of  exosmosis  and  endosmosis,  therefore,  in  the  living 

'  Le.ons  de  Physiologie  Experimentale,  Paris,  1856,  p.  107. 


816  IMBIBITION    AND    EXHALATION. 

body,  are  regulated  by  the  same  conditions  as  in  artificial  experi- 
ments, but  they  take  place  witb  infinitely  greater  rapidity,  owing  to 
the  movement  of  the  circulating  blood,  and  the  extent  of  contact 
existing  between  the  bloodvessels  and  adjacent  tissues,  "VYe  have  • 
already  seen  that  the  absorption  of  the  same  fluid  is  accomplished 
with  different  degrees  of  rapidity  by  different  animal  substances. 
Accordingly,  though  the  arterial  blood  is  everywhere  the  same  in 
composition,  yet  its  different  ingredients  are  imbibed  in  varying 
quantities  by  the  different  tissues.  Thus,  the  cartilages  absorb 
from  the  circulating  fluid  a  larger  proportion  of  phosphate  of  lime 
than  the  softer  tissues,  and  the  bones  a  larger  proportion  than  the 
cartilages;  and  the  watery  and  saline  ingredients  generally  are 
found  in  different  quantities  in  difierent  parts  of  the  body.  The 
same  animal  membrane,  also,  as  it  has  been  shown  by  experiment, 
will  imbibe  different  substances  with  different  degrees  of  facility. 
Thus,  the  blood,  for  example,  contains  more  chloride  of  sodium 
than  chloride  of  potassium ;  but  the  muscles,  which  it  supplies  with 
nourishment,  contain  more  chloride  of  potassium  than  chloride  of 
sodium.  In  this  way,  the  proportion  of  each  ingredient  derived 
from  the  blood  is  determined,  in  each  separate  tissue,  by  its  special 
absorbing  or  endosmotic  power. 

Furthermore,  we  have  seen  that  albumen,  under  ordinary  condi- 
tions, is  not  endosmotic ;  that  is,  it  will  not  pass  by  transudation 
through  an  animal  membrane.  For  the  same  reason,  the  albumen 
of  the  blood,  in  the  natural  state  of  the  circulation,  is  not  exhaled 
from  the  secreting  surfaces,  but  is  retained  within  the  circulatory 
system,  while  the  watery  and  saline  ingredients  transude  in  varying 
quantities.  But  the  degree  oi pressure  io  which  a  fluid  is  subjected 
has  great  influence  in  determining  its  endosmotic  action.  A  sub- 
stance which  passes  but  slowly  under  a  low  pressure,  may  pass 
much  more  rapidly  if  the  force  be  increased.  Accordingly,  we  find 
that  if  the  pressure  upon  the  blood  in  the  vessels  be  increased,  by 
obstruction  to  the  venous  current  and  backward  congestion  of  the 
capillaries,  then  not  only  the  saline  and  watery  parts  of  the  blood 
pass  out  in  larger  quantities,  but  the  albumen  itself  transudes,  and 
infiltrates  the  neighboring  parts.  It  is  in  this  way  that  albumen 
makes  its  appearance  in  the  urine,  in  consequence  of  obstruction  to 
the  renal  circulation,  and  that  local  oedema  or  general  anasarca 
may  follow  upon  venous  congestion  in  particular  regions,  or  upon 
general  disturbance  of  the  circulation. 

The  processes  of  imbibition  and  exudation,  which  thus  take 


THE    LYMPHATIC    SYSTEM.  317 

place  incessantly  tlirougliout  the  body,  are  intimately  connected 
with,  the  action  of  the  great  absorbent  or  lymphatic  system  of  ves- 
sels, which  is  to  be  considered  as  secondary  or  complementary  to 
that  of  the  sanguiferous  circulation. 

The  lymphatics  may  be  regarded  as  a  system  of  vessels,  com- 
mencing in  the  substance  of  the  various  tissues  and  organs,  and 
endowed  with  the  property  of  absorbing  certain  of  their  ingredi- 
ents. Their  commencement  has  been  demonstrated  by  injections, 
more  particularly  in  the  membranous  parts  of  the  body ;  viz.,  in 
the  skin,  the  mucous  membranes,  the  serous  and  synovial  surfaces, 
and  the  inner  tunic  of  the  arteries  and  veins.  They  originate  in 
these  situations  by  vascular  networks,  not  very  unlike  those  of  the 
capillary  bloodvessels.  Notwithstanding  this  resemblance  in  form 
between  the  capillary  plexuses  of  the  lymphatics  and  the  blood- 
vessels, it  is  most  probable  that  they  are  anatomically  distinct  from 
each  other.  It  has  been  supposed,  at  various  times,  that  there 
might  be  communications  between  them,  and  even  that  the  lymph- 
atic plexus  might  be  a  direct  continuation  of  that  originating  from 
the  smaller  arteries ;  but  this  has  never  been  demonstrated,  and  it 
is  now  almost  universally  conceded  that  the  anatomical  evidence  is 
in  favor  of  a  complete  separation  between  the  two  vascular  systems. 

Commencing  in  this  way  in  the  substance  of  the  tissues,  by  a 
vascular  network,  the  minute  lymphatics  unite  gradually  with  each 
other  to  form  larger  vessels ;  and,  after  continuing  their  course  for 
a  certain  distance  from  without  inward,  they  enter  and  are  distri- 
buted to  the  substance  of  the  lymphatic  glands.  According  to  M. 
Colin,'  beside  the  more  minute  and  convoluted  vessels  in  each  gland, 
there  are  always  some  larger  branches  which  pass  directly  through 
its  substance,  from  the  afi'erent  to  the  efferent  vessels ;  so  that  only 
a  portion  of  the  lymph  is  distributed  to  its  ultimate  glandular 
plexus.  This  portion,  however,  in  passing  through  the  organ,  is 
evidently  subjected  to  some  glandular  influence,  which  may  serve 
to  modify  its  composition. 

After  passing  through  these  glandular  organs,  the  lymphatic 
vessels  unite  into  two  great  trunks  (Fig.  43) :  the  thoracic  duct,  which 
collects  the  fluid  from  the  absorbents  of  the  lower  extremities,  the 
intestines  and  other  abdominal  organs,  the  chest,  the  left  upper 
extremity,  and  the  left  side  of  the  head  and  neck,  and  terminates 
in  the  left  subclavian  vein,  at  the  junction  of  the  internal  jugular ; 
and  the  right  lymphatic  duct,  which  collects  the  fluid  from  the  right 

■  Physiologic  coniparGe  des  Animaux  clomestiqueB, .Paris,  185(),  vol.  ii.  p.  C8. 


818  IMBIBITION    AND    EXHALATION. 

upper  extremity  and  right  side  of  the  head  and  neck,  and  joins  the 
right  subclavian  vein  at  its  junction  with  the  corresponding  jugular. 
Thus  nearly  all  the  lymph  from  the  external  parts,  and  the  whole 
of  that  from  the  abdominal  organs,  passes,  by  the  thoracic  duct, 
into  the  left  subclavian  vein. 

We  already  know  that  the  lymphatic  vessels  are  not  to  be  re- 
garded as  the  exclusive  agents  of  absorption.  On  the  contrary, 
absorption  takes  place  by  the  bloodvessels  even  more  rapi-dly  and 
abundantly  than  by  the  lymphatics.  Even  the  products  of  diges- 
tion, including  the  chyle,  are  taken  up  from  the  intestine  in  large 
proportion  by  the  bloodvessels,  and  are  only  in  part  absorbed  by 
the  lymphatics.  But  the  main  peculiarity  of  the  lymphatic  system 
is  that  its  vessels  all  pass  in  one  direction,  viz.,  from  without  inward, 
and  none  from  within  outward.  Consequently  there  is  no  circula- 
tion of  the  lymph,  strictly  speaking,  like  that  of  the  blood,  but  it 
is  all  supplied  by  exudation  and  absorption  from  the  tissues. 

The  lymph  has  been  obtained,  in  a  state  of  purity,  by  various 
experimenters,  by  introducing  a  canula  into  the  thoracic  duct,  at 
the  root  of  the  neck,  or  into  large  lymphatic  trunks  in  other  parts 
of  the  body.  It  has  been  obtained  by  Rees  from  the  lacteal  vessels 
and  the  lymphatics  of  the  leg  in  the  ass,  by  Colin  from  the  lacteals 
and  thoracic  duct  of  the  ox,  and  from  the  lymphatics  of  the  neck 
in  the  horse.  We  have  also  obtained  it,  on  several  different  occa- 
sions, from  the  thoracic  duct  of  the  dog  and  of  the  goat. 

The  analysis  of  these  fluids  shows  a  remarkable  similarity  in 

constitution  between  them    and  the  plasma  of  the  blood.     They 

contain  water,  fibrin,  albumen,  fatty  matters,  and  the  usual  saline 

substances  of  the  animal  fluids.     At  the  same  time,  the  lymph  is 

very  much  poorer  in  albuminous  ingredients  than  the  blood.     The 

following  is  an  analysis  by  Lassaigne,^  of  the  fluid  obtained  from 

the  thoracic  duct  of  the  cow  : — 

Parts  per  thousand. 

Water 964.0 

,                  Fibrin 0.9 

Albumen          . 28.0 

Fat          .         .         .         • 0.4 

Chloride  of  sodium          .......  5.0 

Carbonic  -^ 

Phosphate  and  >■  of  soda 1-2 

Sulphate  -' 

Phosphate  of  lime 0.5 

1000.0 
•  Colin,  Physiologie  comparee  des  Animaux  domestiques,  vol.  ii.  p.  111. 


THE    LYMPHATIC    SYSTEM.  319 

It  tlius  appears  that  both  the  fibrin  and  the  albumen  of  the  blood 
actually  transude  to  a  certain  extent  from  the  bloodvessels,  even  in 
the  ordinary  condition  of  the  circulatory  system.  But  this  transuda- 
tion takes  place  in  so  small  a  quantity  that  the  albuminous  matters 
are  all  taken  up  again  by  the  lymphatic  vessels,  and  do  not  appear 
in  the  excreted  fluids. 

The  first  important  peculiarity  which  is  noticed  in  regard  to  the 
fluid  of  the  lymphatic  system,  especially  in  the  carnivorous  animals, 
is  that  it  varies  very  much,  both  in  appearance  and  constitution,  at 
different  times.  In  the  ruminating  and  graminivorous  animals, 
such  as  the  sheep,  ox,  goat,  horse,  &c.,  it  is  either  opalescent  in 
appearance,  with  a  slight  amber  tinge,  or  nearly  transparent  and 
colorless.  In  the  carnivorous  animals,  such  as  the  dog  and  cat,  it 
is  also  opaline  and  amber  colored,  in  the  intervals  of  digestion,  but 
soon  after  feeding  becomes  of  a  dense,  opaque,  milky  white,  and  con- 
tinues to  present  that  appearance  until  the  processes  of  digestion 
and  intestinal  absorption  are  complete.  It  then  regains  its  original 
aspect,  and  remains  opaline  or  semi-transparent  until  digestion  is 
again  in  progress. 

The  cause  of  this  variable  constitution  of  the  fluid  discharged 
by  the  thoracic  duct  is  the  absorption  of  fatty  substances  from  the 
intestine  during  digestion.  Whenever  fatty  substances  exist  in  con- 
siderable quantity  in  the  food,  they  are  reduced,  by  the  process  of 
digestion,  to  a  white,  creamy  mixture  of  molecular  fat,  suspended 
in  an  albuminous  menstruum.  The  mixture  is  then  absorbed  by 
the  lymphatics  of  the  mesentery,  and  transported  by  them  through 
the  thoracic  duct  to  the  subclavian  vein.  While  this  absorption  is 
going  on,  therefore,  the  fluid  of  the  thoracic  duct  alters  its  appear- 
ance, becomes  white  and  opaque,  and  is  then  called  chyle;  so  that 
there  are  two  different  conditions,  in  which  the  contents  of  the  great 
lymphatic  trunks  present  different  appearances.  In  the  fasting 
condition,  these  vessels  contain  a  semi-transparent,  or  opaline  and 
nearly  colorless  lymph ;  and  during  digestion,  an  opaque,  milky 
chyle.  It  is  on  this  account  that  the  lymphatics  of  the  mesentery 
are  called  "  lacteals." 

The  chyle,  accordingly,  is  nothing  more  than  the  lymph  which 
is  constantly  absorbed  by  the  lymphatic  system  everywhere,  with 
the  addition  of  more  or  less  fatty  ingredients  taken  up  from  the 
intestine  during  the  digestion  of  food. 

The  results  of  analysis  show  positively  that  the  varying  appear- 
ance of  the  lymphatic  fluids  is  really  due  to  this  cause ;  for  though 


820  IMBIBITION    AND    EXHALATION. 

tlie  chyle  is  also  richer  than  the  lymph  in  albuminous  matters,  the 
principal  difference  between  them  consists  in  the  proportion  of  fat. 
This  is  shown  by  the  following  comparative  analysis  of  the  lymph 
and  chyle  of  the  ass,  by  Dr.  Eees : ' — 


Lymph. 

Chyle. 

Water    .         .         .         . 

.     965.36 

902.37 

Albumen 

.       12.00 

35.16 

Fibrin     . 

...         1.20 

3.70 

Spirit  extract 

2.40 

3.32 

Water  extract 

.       13.19 

12.33 

Fat         .         .         . 

.    traces. 

36.01 

Saline  matter 

5.85 

7.11 

1,000.00  1,000.00 

When  a  canula,  accordingly,  is  introduced  into  the  thoracic  duct 
at  various  periods  after  feeding,  the  fluid  which  is  discharged  varies 
considerably,  both  in  appearance  and  quantity.  We  have  found 
that,  in  the  dog,  the  fluid  of  the  thoracic  duct  never  becomes  quite 
transparent,  but  retains  a  very  marked  opaline  tinge  even  so  late 
as  eighteen  hours  after  feeding,  and  at  least  three  days  and  a  half 
after  the  introduction  of  fat  food.  Soon  after  feeding,  however,  as 
we  have  already  seen,  it  becomes  whitish  and  opaque,  and  remains 
so  while  digestion  and  absorption  are  in  progress.  It  also  becomes 
more  abundant  soon  after  the  commencement  of  digestion,  but 
diminishes  again  in  quantity  during  its  latter  stages.  We  have 
found  the  lymph  and  chyle  to  be  discharged  from  the  thoracic  duct, 
in  the  dog,  in  the  following  quantities  per  hour,  at  different  periods 
of  digestion.  The  quantities  are  calculated  in  proportion  to  the 
entire  weight  of  the  animal. 

Per  Thousand  Parts. 
3|  hours  after  feeding       .         .         .         .         .         .2.45 

7        "        «'  " 2.20 

13        "        "  " 0.99 

18        "         "  " 1.15 

18^      "        "  " 1.99 

It  would  thus  appear  that  the  hourly  quantity  of  lymph,  after 
diminishing  during  the  latter  stages  of  digestion,  increases  again 
somewhat,  about  the  eighteenth  hour,  though  it  is  still  considera- 
bly less  abundant  than  while  digestion  was  in  active  progress. 

The  lymph  obtained  from  the  thoracic  duct  at  all  periods  coagu- 
lates soon  after  its  withdrawal,  owing  to  the  fibrin  which  it  contains 

'  In  Colin,  op.  cit.,  vol.  ii.  p.  18. 


THE    LYMPHATIC    SYSTEM.  321 

in  small  quantity.  After  coagulation,  a  separation  takes  place  be- 
tween the  clot  and  serum,  precisely  as  in  the  case  of  blood. 

The  movement  of  the  lymph  in  the  lymphatic  vessels,  from  the 
extremities  toward  the  heart,  is  accomplished  by  various  forces. 
The  first  and  most  important  of  these  forces  is  that  by  which  the 
fluids  are  originally  absorbed  by  the  lymphatic  capillaries.  Through- 
out the  entire  extent  of  the  lymphatic  system,  an  extensive  process 
of  endosmosis  is  incessantly  going  on,  by  which  the  ingredients  of 
the  lymph  are  imbibed  from  the  surrounding  tissues,  and  com- 
pelled to  pass  into  the  lymphatic  vessels.  The  lymphatics  are  thus 
filled  at  their  origin ;  and,  by  mere  force  of  accumulation,  the  fluids 
are  then  compelled,  as  their  absorption  continues,  to  discharge 
themselves  into  the  large  veins  in  which  the  lymphatic  trunks 
terminate. 

The  movement  of  the  fluids  through  the  lymphatic  system  is 
also  favored  by  the  contraction  of  the  voluntary  muscles  and  the 
respiratory  motions  of  the  chest.  For  as  the  lymphatic  vessels  are 
provided  with  valves,  arranged  like  those  of  the  veins,  opening 
toward  the  heart  and  shutting  backward  toward  the  extremities, 
the  alternate  compression  and  relaxation  of  the  adjacent  muscles, 
and  the  expansion  and  collapse  of  the  thoracic  parietes,  must  have 
the  same  effect  upon  the  movement  of  the  lymph  as  upon  that  of 
the  venous  blood.  By  these  different  influences  the  chyle  and 
lymph  are  incessantly  carried  from  without  inward,  and  discharged, 
in  a  slow  but  continuous  stream,  into  the  returning  current  of  the 
venous  blood. 

The  entire  quantity  of  the  lymph  and  chyle  has  been  found,  by 
direct  experiment,  to  be  very  much  larger  than  was  previously 
anticipated.  M.  Colin'  measured  the  chyle  discharged  from  the 
thoracic  duct  of  an  ox  during  twenty -four  hours,  and  found  it  to 
exceed  eighty  pounds.  In  other  experiments  of  the  same  kind,  he 
obtained  still  larger  quantities.^  From  two  experiments  on  the 
horse,  extending  over  a  period  of  twelve  hours  each,  he  calculates 
the  quantity  of  chyle  and  lymph  in  this  animal  as  from  twelve  to 
fifteen  thousand  grains  per  hour,  or  between  forty  and  fifty  pounds 
per  day.  But  in  the  ruminating  animals,  according  to  his  observa- 
tions, the  quantity  is  considerably  greater.  In  an  ordinary-sized 
cow,  the  smallest  quantity  obtained  in  an  experiment  extending  over 

«  Gazette  Hehdomadaire,  April  24,  1857,  p.  285. 
*  Colin,  op.  cit.,  vol.  ii.  p.  100. 

21 


322  IMBIBITION    AND    EXHALATION. 

a  period  of  twelve  hours,  was  a  little  over  9,000  grains  in  fifteen 
minutes;  that  is,  five  pounds  an  hour,  or  120  pounds  per  day.  In 
another  experiment,  with  a  young  bull,  he  actually  obtained  a  little 
over  100  pounds  from  a  fistula  of  the  thoracic  duct,  in  twenty-four 
hours. 

We  have  also  obtained  similar  results  by  experiments  upon  the 
dog  and  goat.  In  a  young  kid,  weighing  fourteen  pounds,  we  have 
obtained  from  the  thoracic  duct  1890  grains  of  lymph  in  three 
hours  and  a  half.  This  quantity  would  represent  540  grains  in  an 
hour,  and  12,690  grains,  or  1.85  pounds  in  twenty-four  hours;  and 
in  a  ruminating  animal  weighing  1000  pounds,  this  would  corre- 
spond to  132  pounds  of  lymph  and  chyle  discharged  by  the  thoracic 
duct  in  the  course  of  twenty-four  hours. 

The  average  of  all  the  results  obtained  by  us,  in  the  dog,  at  dif- 
ferent periods  after  feeding,  gives  very  nearly  four  and  a  half  per 
cent,  of  the  entire  weight  of  the  animal,  as  the  total  daily  quantity 
of  lymph  and  chyle.  This  is  substantially  the  same  result  as  that 
obtained  by  Colin,  in  the  horse;  and  for  a  man  weighing  140 
pounds,  it  would  be  equivalent  to  between  six  and  six  and  a  half 
pounds  of  lymph  and  chyle  per  day. 

But  of  this  quantity  a  considerable  portion  consists  of  the  chyle 
which  is  absorbed  from  the  intestines  during  the  digestion  of  fatty 
substances.  If  we  wish,  therefore,  to  ascertain  the  total  amount  of 
the  lymph,  separate  from  that  of  the  chyle,  the  calculation  should 
be  based  upon  the  quantity  of  fluid  obtained  from  the  thoracic 
duct  in  the  intervals  of  digestion,  when  no  chyle  is  in  process  of 
absorption.  We  have  seen  that  in  the  dog,  eighteen  hours  after 
feeding,  the  lymph,  which  is  at  that  time  opaline  and  semi-transpa- 
rent, is  discharged  from  the  thoracic  duct,  in  the  course  of  an  hour, 
in  a  quantity  equal  to  1.15  parts  per  thousand  of  the  entire  weight 
of  the  animal.  In  twenty-four  hours  this  would  amount  to  27.6 
parts  per  thousand ;  and  for  a  man  weighing  140  pounds  this  would 
give  3.864  pounds  as  the  total  daily  quantity  of  the  lymph  alone. 

It  will  be  seen,  therefore,  that  the  processes  of  exudation  and 
absorption,  which  go  on  in  the  interior  of  the  body,  produce  a  very 
active  interchange  or  internal  circulation  of  the  animal  fluids,  which 
may  be  considered  as  secondary  to  the  circulation  of  the  blood. 
For  all  the  digestive  fluids,  as  we  have  found,  together  with  the  bile 
discharged  into  the  intestine,  are  reabsorbed  in  the  natural  process 
of  digestion  and  again  enter  the  current  of  the  circulation.  These 
fluids,  therefore,  pass  and  repass  through  the  mucous  membrane  of- 


THE    LYMPHATIC    SYSTEM.  323 

the  alimentary  canal  and  adjacent  glands,  becoming  somewhat 
altered  in  constitution  at  each  passage,  but  still  serving  to  renovate 
alternately  the  constitution  of  the  blood  and  the  ingredients  of  the 
digestive  secretions.  Furthermore  the  elements  of  the  blood  itself 
also  transude  in  part  from  the  capillary  vessels,  and  are  again  taken 
up,  by  absorption,  by  the  lymphatic  vessels,  to  be  finally  restored 
to  the  returning  current  of  the  venous  blood,  in  the  immediate 
neighborhood  of  the  heart. 

The  daily  quantity  of  all  the  fluids,  thus  secreted  and  reabsorbed 
during  twenty-four  hours,  will  enable  us  to  estimate  the  activity 
with  which  endosmosis  and  exosmosis  go  on  in  the  living  bodv. 
In  the  following  table,  the  quantities  are  all  calculated  for  a  man 
weighing  140  pounds. 

Secreted  and  Reabsorbed  during  24  hours. 
Saliva  20,164  grains,  or     2.880  pounds. 

Gastric  juice        98,000       "        "    14.000       " 
Bile  16.940       "        "      2.420       " 

Pancreatic  juice  13,104       "        "      1.872       " 
Lymph  27,048       "        "      3.864       •' 


25.036 


A  little  over  twenty-five  pounds,  therefore,  of  the  animal  fluids 
transude  through  the  internal  membranes  and  are  restored  to  the 
blood  by  reabsorption  in  the  course  of  a  single  day.  It  is  by  this 
process  that  the  natural  constitution  of  the  parts,  though  constantly 
changing,  is  still  maintained  in  its  normal  condition  by  the  move- 
ment of  the  circulating  fluids,  and  the  incessant  renovation  of  their 
nutritious  materials. 


824  SECRETION. 


CHAPTER   XVI. 

SECRETION. 

We  have  already  seen,  in  a  previous  chapter,  how  the  elements  of 
the  blood  are  absorbed  by  the  tissues  during  the  capillary  circula- 
tion, and  assimilated  by  them  or  converted  into  their  own  substance. 
In  this  process,  the  inorganic  or  saline  matters  are  mostly  taken  up 
unchanged,  and  are  merely  appropriated  by  the  surrounding  parts  in 
particular  quantities;  while  the  organic  substances  are  transformed 
into  new  compounds,  characteristic  of  the  different  tissues  by  which 
they  are  assimilated.  In  this  way  the  various  tissues  of  the  body, 
though  they  have  a  different  chemical  composition  from  the  blood, 
are  nevertheless  supplied  by  it  w4th  appropriate  ingredients,  and 
their  nutrition  constantly  maintained. 

Beside  this  process,  which  is  known  by  the  name  of  "  assimila- 
tion," there  is  another  somewhat  similar  to  it,  which  takes  place  in 
the  different  glandular  organs,  known  as  the  process  of  secretion.  It 
is  the  object  of  this  function  to  supply  certain  fluids,  differing  in 
chemical  constitution  from  the  blood,  which  are  required  to  assist 
in  various  physical  and  chemical  actions  going  on  in  the  body. 
These  secreted  fluids,  or  "secretions,"  as  they  are  called,  vary  in 
consistency,  density,  color,  quantity,  and  reaction.  Some  of  them 
are  thin  and  watery,  like  the  tears  and  the  perspiration ;  others  are 
viscid  and  glutinous,  like  mucus  and  the  pancreatic  fluid.  They 
are  alkaline  like  the  saliva,  acid  like  the  gastric  juice,  or  neutral 
like  the  bile.  Each  secretion  contains  water  and  the  inorganic  salts 
of  the  blood,  in  varying  proportions;  and  is  furthermore  distin- 
guished by  the  presence  of  some  peculiar  animal  substance  which 
does  not  exist  in  the  blood,  but  which  is  produced  by  the  secreting 
action  of  the  glandular  organ.  As  the  blood  circulates  through  the 
capillaries  of  the  gland,  its  watery  and  saline  constituents  transude 
in  certain  quantities,  and  are  discharged  into  the  excretory  duct. 
At  the  same  time,  the  glandular  cells,  which  have  themselves  been 
nourished  by  the  blood,  produce  a  new  substance  by  the  catalytic 


SECRETION.  325 

transformation  of  their  organic  constituents;  and  this  new  substance 
is  discharged  also  into  the  excretory  duct  and  mingled  with  the 
other  ingredients  of  the  secreted  fluid.  A  true  secretion,  therefore, 
is  produced  only  in  its  own  particular  gland,  and  cannot  be  formed 
elsewhere,  since  the  glandular  cells  of  that  organ  are  the  only 
ones  capable  of  producing  its  most  characteristic  ingredient.  Thus 
pepsine  is  formed  only  in  the  tubules  of  the  gastric  mucous  mem- 
brane, pancreatine  only  in  the  pancreas,  tauro-cholate  of  soda  only 
in  the  liver. 

One  secreting  gland,  consequently,  can  never  perform  vicariously 
the  office  of  another.  Those  instances  which  have  been  from  time 
to  time  reported  of  such  an  unnatural  action  are  not,  properly 
speaking,  instances  of  "vicarious  secretion;"  but  only  eases  in 
which  certain  substances,  already  existing  in  the  blood,  have  made 
their  appearance  in  secretions  to  which  they  do  not  naturally  belong. 
Thus  cholesterine,  which  is  produced  in  the  brain  and  is  taken  up 
from  it  by  the  blood,  usually  passes  out  with  the  bile ;  but  it  may 
also  appear  in  the  fluid  of  hydrocele,  or  in  inflammatory  exuda- 
tions. The  sugar,  again,  which  is  produced  in  the  liver  and  taken 
up  by  the  blood,  when  it  accumulates  in  large  quantity  in  the  cir- 
culating fluid,  may  pass  out  with  the  urine.  The  coloring  matter 
of  the  bile,  in  cases  of  biliary  obstruction,  may  be  reabsorbed,  and 
so  make  its  appearance  in  the  serous  fluids,  or  even  in  the  perspira- 
tion. In  these  instances,  however,  the  unnatural  ingredient  is  not 
actually  produced  by  the  kidneys,  or  the  perspiratory  glands,  but 
is  merely  supplied  to  them,  already  formed,  by  the  blood.  Cases 
of  "vicarious  menstruation"  are  simply  capillary  hemorrhages 
which  take  place  from  various  mucous  membranes,  owing  to  the 
general  disturbance  of  the  circulation  in  amenorrhoea.  A  true 
secretion,  however,  is  always  confined  to  the  gland  in  which  it 
naturally  originates. 

The  force  by  which  the  different  secreted  fluids  are  prepared  in 
the  glandular  organs,  and  discharged  into  their  ducts,  is  a  pecxiliar 
one,  and  resident  only  in  the  glands  themselves.  It  is  not  simply 
a  process  of  filtration,  in  which  the  ingredients  of  the  secretion 
exude  from  the  bloodvessels  by  exosmosis  under  the  influence  of 
pressure ;  since  the  most  characteristic  of  these  ingredients,  as  we 
have  already  mentioned,  do  not  pre-exist  in  the  blood,  but  are 
formed  in  the  substance  of  the  gland  itself.  Substances,  even, 
which  already  exist  in  the  blood  in  a  soluble  form,  may  not  have 
the  power  of  passing  out  through  the  glandular  tissue.     Bernard 


326  SECRETION-. 

has  found'  that  ferrocyanide  of  potassium,  when  injected  into  the 
jugular  vein,  though  it  appears  with  great  facility  in  the  urine, 
does  not  pass  out  with  the  saliva ;  and  even  that  ar  solution  of 
the  same  salt,  injected  into  the  duct  of  the  parotid  gland,  is  ab- 
sorbed, taken  up  by  the  blood,  and  discharged  with  the  urine ;  but 
does  not  appear  in  the  saliva,  even  of  the  gland  into  which  it  has 
been  injected.  The  force  with  which  the  secreted  fluids  accumulate 
in  the  salivary  ducts  has  also  been  shown  by  Ludwig's  experi- 
ments^ to  be  sometimes  greater  than  the  pressure  in  the  bloodves- 
sels. This  author  found,  by  applying  mercurial  gauges  at  the  same 
time  to  the  duct  of  Steno  and  to  the  artery  of  the  parotid  gland,  that 
the  pressure  in  the  duct  from  the  secreted  saliva  was  considerably 
greater  than  that  in  the  artery  from  the  circulating  blood ;  so  that 
the  passage  of  the  secreted  fluids  had  really  taken  place  in  a  direc- 
tion contrary  to  that  which  would  have  been  caused  by  the  simple 
influence  of  pressure. 

The  process  of  secretion,  therefore,  is  one  which  depends  upon 
the  peculiar  anatomical  and  chemical  constitution  of  the  glandular 
tissue  and  its  secreting  cells.  These  cells  have  the  property  of 
absorbing  and  transmitting  from  the  blood  certain  inorganic  and 
saline  substances,  and  of  producing,  by  chemical  metamorphosis, 
certain  peculiar  animal  matters  from  their  own  tissue...  These  sub- 
stances are  then  mingled  together,  dissolved  in  the  watery  fluids 
of  the  secretion,  and  discharged  simultaneously  by  the  excretory 
duct. 

All  the  secreting  organs  vary  in  activity  at  different  periods. 
Sometimes  they  are  nearly  at  rest;  while  at  certain  periods  they 
become  excited,  under  the  influence  of  an  occasional  or  periodical 
stimulus,  and  then  pour  out  their  secretion  with  great  rapidity  and  in 
large  quantity.  The  perspiration,  for  example,  is  usually  so  slowly 
secreted  that  it  evaporates  as  rapidly  as  it  is  poured  out,  and  the 
surface  of  the  skin  remains  dry ;  but  under  the  influence  of  unusual 
bodily  exercise  or  mental  excitement  it: is,  secreted  much  faster 
than  it  can  evaporate,  and  the  whole  integument  becomes  covered 
with  moisture.  The  gastric  juice,  again,  in  the  intervals  of  digestion, 
is  either  not  secreted  at  all,  or  is  produced  in  a  nearly  inappreciable 
quantity;  but  on  the  introduction  of  food  into  the  stomach,  it  is 
immediately  poured  out  in  such  abundance,  that  between  two  and 
three  ounces  may  be  collected  in  a  quarter  of  an  hour. 

•  Le(;ons  de  Physiologie  Experimentale.     Paris,  1856,  tome  ii^p.  ■96'e<  *°7. 
2  Ibid.,  p.  10(5. 


MUCUS.  327 

The  principal  secretions  met  with  in  the  animal  body  are  as 
follows : — 

1.  Mucus.  6.  Saliva. 

2.  Sebaceous  matter.  7.  Gastric  juice. 

3.  Perspiration.  8.  Pancreatic  juice. 

4.  The  tears.  9.  Intestinal  juice. 

5.  The  milk.  10.  Bile. 

The  last  five  of  these  fluids  have  already  been  described  in  the 
preceding  chapters.  We  shall  therefore  only  require  to  examine 
at  present  the  five  following,  viz.,  mucus,  sebaceous  matter,  per- 
spiration, the  tears,  and  the  milk,  together  with  some  peculiarities 
in  the  secretion  of  the  bile. 

1.  Mucus. — ^Nearly  all  the  mucous  membranes  are  provided  with 
follicles  or  glandulee,  in  which  the  mucus  is  prepared.  These  folli- 
cles are  most  abundant  in  the  lining  membrane  of  the  mouth,  nares, 
pharynx,  oesophagus,  trachea  and  bronchi,  vagina,  and  male  urethra. 
They  are  generally  of  a  compound  form,  consisting  of  a  number  of 
secreting  sacs  or  cavities,  terminating  at  one  end  in  a  blind  ex- 
tremity, and  opening  by  the  other  into  a  common  duct  by  which 
the  secreted  fluid  is  discharged.  Each  ultimate  secreting  sac  or 
follicle  is  lined  with  glandular  epithelium  (Fig.  102),  and  surround- 
ed on  its  external  surface  by  a  network  of  capillary  bloodvessels. 
These  vessels,  penetrating  deeply  into  the  -p.    ,  „„ 

interstices  between  the  follicles,  bring  the 
blood  nearly  into  contact  with  the  epithelial 
cells  lining  its  cavity.  It  is  these  cells 
which  prepare  the  secretion,  and  discharge 
it  afterward  into  the  commencement  of  the 
excretory  duct.  I-ollicles    of    a    com- 

The   mucus,   produced   in   the    manner    pound  mucous  glandule. 

.  ,  .,,.  ,  ,,  n     •  1        From  the  human  subject.     (Aftei 

above  described,  is  a  clear,  colorless  fluid,  K6iiiker.)-a.  Membrane  of  the 
which  is  poured  out  in  larger  or  smaller    fouicie.  b,  c.  Epithelium  of  the 

,  p  f»       1  same. 

quantity  on  the   suriace   oi    the   mucous 

membranes.  It  is  distinguished  from  other  secretions  by  its  vis- 
cidity, which  is  its  most  marked  physical  property,  and  which 
depends  on  the  presence  of  a  peculiar  animal  matter,  known  under 
the  name  of  mucosine.  "When  unmixed  with  other  animal  fluids, 
this  viscidity  is  so  great  that  the  mucus  has  nearly  a  semi-solid  or 
gelatinous  consistency.  Thus,  the  mucus  of  the  mouth,  when  ob- 
tained unmixed  with  the  secretions  of  the  salivary  glands,  is  so 


828 


SECRETION. 


tough  and  adliesive  that  the  vessel  containing  it  may  be  turned 
upside  down  without  its  running  out.  The  mucus  of  the  cervix 
uteri  has  a  similar  firm  consistency,  so  as  to  block  up  the  cavity 
of  this  part  of  the  organ  with  a  semi-solid  gelatinous  mass.  Mucus 
is  at  the  same  time  exceedingly  smooth  and  slippery  to  the  touch, 
so  that  it  lubricates  readily  the  surfaces  upon  which  it  is  exuded, 
and  facilitates  the  passage  of  foreign  substances,  while  it  defends 
the  mucus  membrane  itself  from  injury. 

The  composition  of  mucus,  according  to  the  analyses  of  Nasse,' 
is  as  follows : — 

Composition  of  Pulmonary  Mucus. 
Water 955.52 


Animal  matter 

Fat 

Chloride  of  sodium  . 
Phosphates  of  soda  and  potassa 
Sulphates  "  " 

Carbonates        "  " 


33.57 
2.89 
5.83 
1.05 
0.G5 
0.49 


1000.00 
The  animal  matter  of  mucus  is  insoluble  in  water ;  and  conse- 
quently mucus,  when  dropped  into  water,  does  not  mix  with  it,  but 
is  merely  broken  up  by  agitation  into  gelatinous  threads  and  flakes, 
which  subside  after  a  time  to  the  bottom.  It  is  miscible,  however, 
to  some  extent,  with  other-  animal  fluids,  and  may  be  incorporated 
with  them,  so  as  to  become  thinner  and  more  dilute.  It  readily 
takes  on  putrefactive  changes,  and  communicates  them  to  other 
organic  substances  with  which  it  may  be  in  contact. 

The  varieties  of  mucus  found  in  different  parts  of  the  body  are 
probably  not  identical  in  composition,  but  differ  a  little  in  the  cha- 
racter of  their  principal  organic  ingredient,  as  well  as  in  the  pro- 
portions of  their  saline  constituents.  The  function  of  mucus  is  for 
the  most  part  a  physical  one,  viz.,  to  lubricate  the  mucous  surfaces, 
to  defend  them  from  injury,  and  to  facilitate  the  passage  of  foreign 
substances  through  their  cavities. 


2.  Sebaceous  Matter. — The  sebaceous  matter  is  distinguished 
by  containing  a  very  large  proportion  of  fatty  or  oily  ingredients. 
There  are  three  varieties  of  this  secretion  met  with  in  the  body, 
viz.,  one  produced  by  the  sebaceous  glands  of  the  skin,  another 
by  the  ceruminous  glands  of  the  external  auditory  meatus,  and 
a  third  by  the  Meibomian  glands  of  the  eyelid.     The  sebaceous 

'  Simon's  Chemistry  of  Man,  Philada.,  1843,  p.  352. 


SEBACEOUS    MATTER. 


329 


Fig.  103. 


glands  of  the  skin  are  found  most  abundantly  in  those  parts  whicli 
are  tMckly  covered  with  hairs,  as  well  as  on  the  face,  the  labia 
minora  of  the  female  generative  organs,  the  glans  penis,  and  the 
prepuce.  They  consist  sometimes  of  a  simple  follicle,  or  flask- 
shaped  cavity,  opening  by  a  single  orifice ;  but  more  frequently  of 
a  number  of  such  follicles  grouped  round  a  common  excretory  duct. 
The  duct  nearly  always  opens  just  at  the  root  of  one  of  the  hairs, 
which  is  smeared  more  or  less  abundantly 
with  its  secretion.  Each  follicle,  as  in  the 
case  of  the  mucous  glandules,  is  lined 
with  epithelium,  and  its  cavity  is  filled 
with  the  secreted  sebaceous  matter. 

In  the  Meibomian  glands  of  the  eye- 
lid (Fig.  103),  the  follicles  are  ranged 
along  the  sides  of  an  excretory  duct, 
situated  just  beneath  the  conjunctiva,  on 
the  posterior  surface  of  the  tarsus,  and 
opening  upon  its  free  edge,  a  little  be- 
hind the  roots  of  the  eyelashes.  The 
ceruminous  glands  of  the  external  audi- 
tory meatus,  again,  have  the  form  of  long 
tubes,  which  terminate,  at  the  lower  part 
of  the  integument  lining  the  meatus,  in 
a  globular  coil,  or  convolution,  covered 
externally  by  a  network  of  capillary  bloodvessels. 

The  sebaceous  matter  of  the  skin  has  the  following  composition, 
according  to  Esenbeck.' 


Meibomian 
Ludovic. 


Glands,      aftei 


Composition  of  Sebacieous  Matter. 
Animal  substances        ...... 

Fatty  matters        ....... 

Phosphate  of  lime        ...... 

Carbonate  of  lime         ...... 

Carbonate  of  magnesia  ..... 

Chloride  of  sodium    I 
Acetate  of  soda,  &c.  ' 


358 

368 

200 

21 

16 

37 

1000 


Owing  to  the  large  proportion  of  stearine  in  the  fatty  ingredients 
of  the  sebaceous  matters,  they  have  a  considerable  degree  of  con- 
sistency. Their  office  is  to  lubricate  the  integument  and  the  hairs, 
to  keep  them  soft  and  pliable,  and  to  prevent  their  drying  up  by 


'  Simon^g  Chemistry  of  Man,  p.  379. 


330 


SECRETIO^r. 


104. 


too  rapid  evaporation.  When  the  sebaceous  glands  of  the  scalp 
are  inactive  or  atrophied,  the  hairs  become  dry  and  brittle,  are 
easily  split  or  broken  off,  and  finally  cease  growing  altogether. 
The  ceruminous  matter  of  the  ear  is  intended  without  doubt  partly 
to  obstruct  the  cavity  of  the  meatus,  and  by  its  glutinous  consist- 
ency and  strong  odor  to  prevent  small  insects  from  accidentally 
introducing  themselves  into  the  meatus.  The  secretion  of  the 
Meibomian  glands,  by  being  smeared  on  the  edges  of  the  eyelids, 
prevents  the  tears  from  running  over  upon  the  cheeks,  and  confines 
them  within  the  cavity  of  the  lachrymal  canals. 

3,  Perspiration. — The  perspiratory  glands  of  the  skin  are  scat- 
tered everywhere  throughout  the  integument,  being  most  abundant 
on  the  anterior  portions  of  the  body.  They  consist  each  of  a  slender 
tube,  about  4^0  of  an  inch  in  diameter,  lined  with  glandular  epi- 
thelium, which  penetrates  nearly  through  the  entire  thickness  of 
the  skin,  and  terminates  below  in  a  globular  coil,  very  similar  in 

appearance  to  that  of  the  cerumi- 
nous glands  of  the  ear.  (Fig.  104.) 
A  network  of  capillary  vessels 
envelops  the  tubular  coil  and  sup- 
plies the  gland  with  the  materials 
necessary  to  its  secretion. 

These  glands  are  very  abundant 
in  some  parts.  On  the  posterior 
portion  of  the  trunk,  the  cheeks, 
and  the  skin  of  the  thigh  and  leg 
there  are,  according  to  Krause,' 
about  500  to  the  square  inch ;  on 
the  anterior  part  of  the  trunk,  the 
forehead,  the  neck,  the  forearm, 
A  pebspiratort  glakd,  with  itsves-    and  the  back  of  the  hand  and  foot 

sels;  magnified  3.5  times.   (After  Todd  and  Bow-      -,  r^r\r\    .        .i  •       i  i 

man. )-a.  Glandular  coil.  J.  Plexus  of  yessels.      1000    tO    the    SqUarC  mch  ;    and  On 

the  sole  of  the  foot  and  the  palm 
of  the  hand  about  2700  in  the  same  space.  According  to  the  same 
observer,  the  whole  number  of  perspiratory  glands  is  not  less  than 
2,300,000,  and  the  length  of  each  tubular  coil,  when  unravelled, 
about  y^g  of  an  inch.  The  entire  length  of  the  glandular  tubing 
must  therefore  be  not  less  than  153,000  inches,  or  about  two  miles 
and  a  half. 

>  Kolliker,  Handbuch  der  Gewebelehre,  Leipzig,  1852.  p.  147. 


PERSPIRATION.  331 

It  is  easy  to  understand,  therefore,  that  a  very  large  quantity  of 
fluid  may  be  supplied  from  so  extensive  a  glandular  apparatus.  It 
results  from  the  researches  of  Lavoisier  and  Seguin^  that  the  ave- 
rage quantity  of  fluid  lost  by  cutaneous  perspiration  during  24 
hours  is  13,500  grains,  or  nearly  two  pounds  avoirdupois.  A  still 
larger  quantity  than  this  may  be  discharged  during  a  shorter  time, 
when  the  external  temperature  is  high  and  the  circulation  active. 
Dr.  Southwood  Smith^  found  that  the  laborers  employed  in  gas 
works  lost  sometimes  as  much  as  3|  pounds'  weight,  by  both  cuta- 
neous and  pulmonary  exhalation,  in  less  than  an  hour.  In  these 
cases,  as  Seguin  has  shown,  the  amount  of  cutaneous  transpiration 
is  about  twice  as  great  as  that  which  takes  place  through  the  lungs. 

The  perspiration  is  a  colorless  watery  fluid,  generally  with  a 
distinctly  acid  reaction,  and  having  a  peculiar  odor,  which  varies 
somewhat  according  to  the  part  of  the  body  from  which  the  speci- 
men is  obtained.  Its  chemical  constitution,  according  to  Ansel- 
mino,^  is  as  follows : — 

Composition  of  the  Perspiration. 

Water 995.00 

Animal  matters,  with  lime .  .10 

Sulphates,  and  substances  soluble  in  water          .         .         .         .  1.05 

Chlorides  of  sodium  and  potassium,  and  spirit-extract         .         .  2.40 

Acetic  acid,  acetates,  lactates,  and  alcohol-extract       .         .         .  1.45 

1000.00 

The  of&ce  of  the  cutaneous  perspiration  is  principally  to  regulate 
the  temperature  of  the  body.  We  have  already  seen,  in  a  preced- 
ing chapter,  that  the  living  body  will  maintain  the  temperature  of 
100°  F.,  though  subjected  to  a  much  lower  temperature  by  the 
surrounding  atmosphere,  in  consequence  of  the  continued  genera- 
tion of  heat  which  takes  place  in  its  interior ;  and  that  if,  by  long 
continued  or  severe  exposure,  the  blood  become  cooled  down  much 
below  its  natural  standard,  death  inevitably  results.  But  the  body 
has  also  the  power  of  resisting  an  unnaturally  high  temperature, 
as  well  as  an  unnaturally  low  one.  If  exposed  to  the  influence  of 
an  atmosphere  warmer  than  100°  F.,  the  body  does  not  become 
heated  up  to  the  temperature  of  the  air,  but  remains  at  its  natural 
standard.  This  is  provided  for  by  the  action  of  the  cutaneous 
glands,  which  are  excited  to  unusual  activity,  and  pour  out  a  large 
quantity  of  watery  fluid  upon  the  skin.     This  fluid  immediately 

'  Milne  Edwards,  Lemons  sur  la  Physiologie,  &c.,  vol.  ii.  p.  623. 
2  Pliilosophy  of  Health,  London,  1838,  chap.  xiii. 
^  Simon.     Op.  cit.,  p.  374. 


332  SECRETION. 

evaporates,  and  in  assuming  the  gaseous  form  causes  so  much  heat 
to  become  latent  that  the  cutaneous  surfaces  are  cooled  down  to 
their  natural  temperature. 

So  long  as  the  air  is  dry,  so  that  evaporation  from  the  surface 
can  go  on  rapidly,  a  very  elevated  temperature  can  be  borne  with 
impunity.  The  workmen  of  the  sculptor  Chantrey  were  in  the 
habit,  according  to  Dr.  Carpenter,  of  entering  a  furnace  in  which 
the  air  was  heated  up  to  350° ;  and  other  instances  have  been  known 
in  which  a  temperature  of  400°  to  600°  has  been  borne  for  a  time 
without  much  inconvenience.  But  if  the  air  be  saturated  with 
moisture,  and  evaporation  from  the  skin  in  this  way  retarded,  the 
body  soon  becomes  unnaturally  warm ;  and  if  the  exposure  be  long 
continued,  death  is  the  result.  It  is  easily  seen  that  horses,  when 
fast  driven,  suffer  much  more  from  a  warm  and  moist  atmosphere 
than  from  a  warm  and  dry  one.  The  experiments  of  Magendie  and 
others  have  shown'  that  quadrupeds  confined  in  a  dry  atmosphere 
suffer  at  first  but  little  inconvenience,  even  when  the  temperature 
is  much  above  that  of  their  own  bodies ;  but  as  soon  as  the  atmo- 
sphere is  loaded  with  moisture,  or  the  supply  of  perspiration  is  ex- 
hausted, the  blood  becomes  heated,  and  the  animal  dies.  Death 
follows  in  these  cases  as  soon  as  the  blood  has  become  heated  up  to 
8°  or  9°  F.,  above  its  natural  standard.  The  temperature  of  110°, 
therefore,  which  is  the  natural  temperature  of  birds,  is  fatal  to  quad- 
rupeds ;  and  we  have  found  that  frogs,  whose  natural  temperature 
is  50°  or  60°,  die  very  soon  if  they  are  kept  in  water  at  100°  F. 

The  amount  of  perspiration  is  liable  to  variation,  as  we  have 
already  intimated,  from  the  variations  in  temperature  of  the  sur- 
rounding atmosphere.  It  is  excited  also  by  unusual  muscular 
exertion,  and  increased  or  diminished  by  various  nervous  condi- 
tions, such  as  anxiety,  irritation,  lassitude,  or  excitement. 

4.  The  Tears. — The  tears  are  produced  by  lobulated  glands 
situated  at  the  upper  and  outer  part  of  the  orbit  of  the  eye,  and 
opening,  by  from  six  to  twelve  ducts,  upon  the  surface  of  the  con- 
junctiva, in  the  fold  between  the  eyeball  and  the  outer  portion  of 
the  upper  lid.  The  secretion  is  extremely  watery  in  its  composition, 
and  contains  only  about  one  part  per  thousand  of  solid  matters, 
consisting  mostly  of  chloride  of  sodium  and  animal  extractive 
matter.     The  office  of  the  lachrymal  secretion  is  simply  to  keep  the 

'  Bernard,  Lectures  on  the  Blood.     Atlee's  translation,  Phila.,  1S54,  p.  25. 


THE    MILK. 


333 


surfaces  of  the  cornea  and  conjunctiva  moist  and  polished,  and  to 
preserve  in  this  way  the  transparency  of  the  parts.  The  tears, 
which  are  constantly  secreted,  are  spread  out  uniformly  over  the 
anterior  part  of  the  eyeball  by  the  movement  of  the  lids  in  wink- 
ing, and  are  gradually  conducted  to  the  inner  angle  of  the  eye. 
Here  they  are  taken  up  by  the  puncta  lachrymalia,  pass  through 
the  lachrymal  canals,  and  are  finally  discharged  into  the  nasal  pas- 
sages beneath  the  inferior  turbinated  bones.  A  constant  supply  of 
fresh  fluid  is  thus  kept  passing  over  the  transparent  parts  of  the 
eyeball,  and  the  bad  results  avoided  which  would  follow  from  its 
accumulation  and  putrefactive  alteration. 

5.  The  Milk. — The  mammary  glands  are  conglomerate  glands 
resembling  closely  in  their  structure  the  pancreas,  the  salivary,  and 
the  lachrymal  glands.  They  consist  of  numerous  secreting  sacs  or 
follicles,  grouped  together  in  lobules,  each  lobule  being  supplied 
with  a  common  excretory  duct,  which  joins  those  coming  from 
adjacent  parts  of  the  gland. 

(Fig.  105.)    In  this  way,  by  Fig.  105. 

their  successive  union,  they 
form  larger  branches  and 
trunks,  until  they  are  reduced 
in  numbers  to  some  15  or  20 
cylindrical  ducts,  the  lactifer- 
ous ducts,  which  open  finally 
by  as  many  minute  orifices 
upon  the  extremity  of  the 
nipple. 

The  secretion  of  the  milk 
becomes  fairly  established  at 
the  end  of  two  or  three  days 
after  delivery,  though  the 
breasts  often  contain  a  milky 

fluid  during  the  latter  part  of  pregnancy.  At  first  the  fluid  dis- 
charged from  the  nipple  is  a  yellowish  turbid  mixture,  which  is 
called  the  colostrum.  It  has  the  appearance  of  being  thinner  than 
the  milk,  but  chemical  examinations  have  shown'  that  it  really  con- 
tains a  larger  amount  of  solid  ingredients  than  the  perfect  secre- 
tion. When  examined  under  the  microscope  it  is  seen  to  contain, 
beside  the  milk-globules  proper,  a  large  amount  of  irregularly  glo 


Glandular   S  t  r  p  c  t  u  k  e    oe    M  a  >i .«  a  . 


'  Lehmann,  op.  cit.,  vol.  ii.  p.  63. 


834 


SECRETION. 


to  sis  of  an  incli  in  diameter, 


bular  or  oval  bodies,  from  tt'so 
which,  are  termed  the  "  colostrum  corpuscles."     (Fig.  106.)     These 

bodies  are  more  yellow  and 


Fig.  106. 


opaque  than  the  true  milk- 
globules,  as  well  as  being  very 
much  larger.  They  have  a 
well  defined  outline,  and  con- 
sist apparently  of  a  group  of 
minute  oily  granules  or  glo- 
bules, imbedded  in  a  mass 
of  organic  substance.  The 
milk-globules  at  this  time 
are  less  abundant  than  after- 
ward, and  of  larger  size, 
measuring  mostly  from  ^o\s 
to  tbVtt  of  an  inch  in  dia- 


CoLOSTRUM    CoKprscLES,  With  milk-globules ; 
from  a  woman,  one  day  after  delivery. 


T5  0  0 

meter. 

At   the  end  of 


day 


or 


two  after  its  first  appearance, 
the  colostrum  ceases  to  be  discharged,  and  is  replaced  by  the  true 
milky  secretion. 

The  milk,  as  it  is  discharged  from  the  nipple,  is  a  white,  opaque 
fluid,  with  a  slightly  alkaline  reaction,  and  a  specific  gravity  of 
about  1030.  Its  proximate  chemical  constitution,  according  to 
Pereira  and  Lehmann,  is  as  follows : — 


Composition  of  Cow's  Milk. 

Water        .        .         .     ' 

Casein       .         .         •   ,    • 

Butter 

Sugar         

Soda  ........ 

Chlorides  of  sodium  and  potassium    .         .         . 

Phosphates  of  soda  and  potassa 

Phosphate  of  lime 

"  "  magnesia      ..... 

"  "  iron 

Alkaline  carbonates  .         .         .         . 


870.2 
44.8 
31.3 

47.7 


6.0 


1000.0 


Human  milk  is  distinguished  from  the  above  by  containing  less 
casein,  and  a  larger  proportion  of  oily  and  saccharine  ingredients. 
The  entire  amount  of  solid  ingredients  is  also  somewhat  less  than 
in  cow's  milk. 


THE    MILK. 


335 


The  casein  is  one  of  the  most  important  ingredients  of  the  milk. 
It  is  an  extremely  nutritious  organic  substance,  which  is  held  in  a 
fluid  form  by  union  with  the  water  of  the  secretion.  Casein  is  not 
coagulable  by  heat,  and  consequently,  milk  may  be  boiled  without 
changing  its  consistency  to  any  considerable  extent.  It  becomes 
a  little  thinner  and  more  fluid  during  ebullition,  owing  to  the  melt- 
ing of  its  oleaginous  ingredients;  and  a  thin,  membranous  film 
forms  upon  its  surface,  consisting  probably  of  a  very  little  albumen, 
which  the  milk  contains,  mingled  with  the  casein.  The  addition  of 
any  of  the  acids,  however,  mineral,  animal,  or  vegetable,  at  once 
coagulates  the  casein,  and  the  milk  becomes  curdled.  Milk  is 
coagulated,  furthermore,  by  the  gastric  juice  in  the  natural  process 
of  digestion,  immediately  after  being  taken  into  the  stomach ;  and 
if  vomiting  occur  soon  after  a  meal  containing  milk,  it  is  thrown. 
off  in  the  form  of  semi-solid,  curd-like  flakes. 

The  mucous  membrane  of  the  calves'  stomach,  or  rennet,  also 
has  the  power  of  coagulating  casein;  and  when  milk  has  been 
curdled  in  this  way,  and  its  watery,  saccharine,  and  inorganic  in- 
gredients separated  by  mechanical  pressure,  it  is  converted  into 
cheese.  The  peculiar  flavor  of  the  different  varieties  of  cheese 
depends  on  the  quantity  and  quality  of  the  oleaginous  ingredients 
which  have  been  entangled  with  the  coagulated  casein,  and  on  the 
alterations  which  these  sub- 
stances have  undergone  by  ^'§'  '^^'^' 
the  lapse  of  time  and  ex- 
posure to  the  atmosphere. 

The  sugar  and  saline  sub- 
stances of  the  milk  are  in 
solution,  together  with  the 
casein  and  water,  forming  a 
clear,  colorless,  homogene- 
ous, serous  fluid.  The  but- 
ter, or  oleaginous  ingredient, 
however,  is  suspended  in 
this  serous  fluid  in  the  form 
of  minute  granules  and 
globules,  the  true  "milk- 
globules."  (Fig.  107.)  These 
globules  are  nearly  fluid  at 
the  temperature  of  the  body,  and  have  a  perfectly  circular  out- 
line.    In  the  perfect  milk,  they  are  very  much  more  abundant  and 


Oo  ' 
08° 


o 
o  Q    Oo  n  ° 

d 


"0°  '"(0)°  0°0%<°^QoOS 


.0      0°°oo 

oO°0°0 
ooo^O  O  o 


o  o 


O  O  O   c 


-^ 


o" 


O 


,Oc 


Milk-Globuli'.s;  from   Barae  woman  as  above, 
four  days  after  delivery.     Secretion  fully  established. 


336  SECRETION, 

smaller  in  size  than  in  the  colostrum;  as  the  largest  of  them  are 
not  over  ^oVg  of  ^^  i^^h  in  diameter,  and  the  greater  number 
about  TXj^TTo  of  ^11  iiich. 

The  following  is  the  composition  of  the  butter  of  cow's  milk, 
according  to  Robin  and  Yerdeil : — 

Margarine    ..........     68 

Oleine 30 

Batyrine      . ^         .       2 

100 

It  is  the  last  of  these  ingredients,  the  butjrine,  which  gives  the 
peculiar  flavor  to  the  butter  of  milk. 

The  milk-globules  have  sometimes  been  described  as  if  each  one 
were  separately  covered  with  a  thin  layer  of  coagulated  casein  or 
albumen.  No  such  investing  membrane,  however,  is  to  be  seen. 
The  milk-globules  are  simply  small  masses  of  semi-fluid  fat,  sus- 
pended by  admixture  in  the  watery  and  serous  portions  of  the 
secretion,  so  as  to  make  an  opaque,  whitish  emulsion.  They  do 
not  fuse  together  when  they  come  in  contact  under  the  microscope, 
simply  because  they  are  not  quite  fluid,  but  contain  a  large  pro- 
portion of  margarine,  which  is  solid  at  ordinary  temperatures  of  the 
body,  and  is  only  retained  in  a  partially  fluid  form  by  the  oleine 
with  which  it  is  associated.  The  globules  may  be  made  to  fuse  with 
each  other,  however,  by  simply  heating  the  milk  and  subjecting  it 
to  gentle  pressure  between  two  slips  of  glass. 

When  fresh  milk  is  allowed  to  remain  at  rest  for  twelve  to  twenty- 
four  hours,  a  large  portion  of  its  fatty  matters  rise  to  the  surface, 
and  form  there  a  dense  and  rich-looking  yellowish-white  layer,  the 
cream,  which  may  be  removed,  leaving  the  remainder  still  opaline, 
but  less  opaque  than  before.  At  the  end  of  thirty-six  to  forty-eight 
hours,  if  the  weather  be  warm,  the  casein  begins  to  take  on  a 
putrefactive  change.  In  this  condition  it  exerts  a  catalytic  action 
upon  the  other  ingredients  of  the  milk,  and  particularly  upon  the 
sugar.  A  pure  watery  solution  of  milk-sugar  (C^^^^fi^^)  may  be 
kept  for  an  indefinite  length  of  time,  at  ordinary  temperatures, 
without  undergoing  any  change.  But  if  kept  in  contact  with  the 
partially  altered  casein,  it  suffers  a  catalytic  transformation,  and  is 
converted  into  lactic  acid  (CgHgOg).  This  unites  with  the  free  soda, 
and  decomposes  the  alkaline  carbonates,  forming  lactates  of  soda 
and  potassa.  After  the  neutralization  of  these  substances  has  been 
accomplished,  the  milk  loses  its  alkaline  reaction  and  begins  to  turn 
sour.     The  free  lactic  acid  then  coagulates  the  casein,  and  the  milk 


SECRETION    OF    THE    BILE.  S37 

is  curdled.  The  altered  organic  matter  also  acts  upon  tlie  olea- 
ginous ingredients,  which  are  partly  decomposed ;  and  the  milk 
begins  to  give  off  a  rancid  odor,  owing  to  the  development  of 
various  volatile  fatty  acids,  among  which  are  butyric  acid,  and  the 
like.  These  changes  are  very  much  hastened  by  a  moderately 
elevated  temperature,  and  also  by  a  highly  electric  state  of  the 
atmosphere. 

The  production  of  the  milk,  like  that  of  other  secretions,  is  liable 
to  be  much  influenced  by  nervous  impressions.  It  may  be  increased 
or  diminished  in  quantity,  or  vitiated  in  quality  by  sudden  emo- 
tions ;  and  it  is  even  said  to  have  been  sometimes  so  much  altered 
in  this  way  as  to  produce  indigestion,  diarrhoea,  and  convulsions  in 
the  infant. 

Simon  found^  that  the  constitution  of  the  milk  varies  from  day  to 
day,  owing  to  temporary  causes ;  and  that  it  undergoes  also  more 
permanent  modifications,  corresponding  with  the  age  of  the  infant. 
He  analyzed  the  milk  of  a  nursing  woman  during  a  period  of  nearly 
six  months,  commencing  with  the  second  day  after  delivery,  and 
repeating  his  examinations  at  intervals  of  eight  or  ten  days.  It 
appears,  from  these  observations,  that  the  casein  is  at  first  in  small 
quantity ;  but  that  it  increases  during  the  first  two  months,  and 
then  attains  a  nearly  uniform  standard.  The  saline  matters  also 
increase  in  a  nearly  similar  manner.  The  sugar,  on  the  contrary, 
diminishes  during  the  same  period ;  so  that  it  is  less  abundant  in 
the  third,  fourth,  fifth  and  sixth  months,  than  it  is  in  the  first  and 
second.  These  changes  are  undoubtedly  connected  with  the  in- 
creasing development  of  the  infant,  which  requires  a  corresponding 
alteration  in  the  character  of  the  food  supplied  to  it.  Finally,  the 
quantity  of  butter  in  the  milk  varies  so  much  from  day  to  day, 
owing  to  incidental  causes,  that  it  cannot  be  said  to  follow  any 
regular  course  of  increase  or  diminution. 

6.  Secretion  of  the  Bile. — The  anatomical  peculiarities  in  the 
structure  of  the  liver  are  such  as  to  distinguish  it  in  a  marked 
degree  from  the  other  glandular  organs.  Its  first  peculiarity  is 
that  it  is  furnished  principally  with  venous  blood.  For,  although 
it  receives  its  blood  from  the  hepatic  artery  as  well  as  from  the 
portal  vein,  the  quantity  of  arterial  blood  with  which  it  is  supplied 
is  extremely  small  in  comparison  with  that  which  it  receives  from 

"  Op.  cit.,  p.  337. 

22 


338 


SECRETION". 


Fi^.  108. 


the  portal  system.  The  blood  which  has  circulated  through  the 
capillaries  of  the  stomach,  spleen,  pancreas,  and  intestine  is  col- 
lected bj  the  roots  of  the  corresponding  veins,  and  discharged  into 
the  portal  vein,  which  enters  the  liver  at  the  great  transverse 
fissure  of  the  organ.  Immediately  upon  its  entrance,  the  portal 
vein  divides  into  two  branches,  right  and  left,  which  supply  the 
corresponding  portions  of  the  liver;  and  these  branches  success- 
ively subdivide  into  smaller  twigs  and  ramifications,  until  they  are 
reduced  to  the  size,  according  to  KoUiker,  of  ts^ott  of  ^^  i^icli  in 
diameter.  These  veins,  with  their  terminal  branches,  are  arranged 
in  such  a  manner  as  to  include  between  them  pentagonal  or 
hexagonal  spaces,  or  portions  of  the  hepatic  substance,  g'g  to  y'j 
of  an  inch  in  diameter  in  the  human  subject,  which  can  readily  be 
distinguished  by  the  naked  eye,  both  on  the  exterior  of  the  organ 
and  by  the  inspection  of  cut  surfaces.  The  portions  of  hepatic 
substance  included  in  this  way  between  the  terminal   branches 

of  the  portal  vein  (Fig.  108) 
are  termed  the  "acini"  or 
"lobules"  of  the  liver;  and 
the  terminal  venous  branches, 
occupying  the  spaces  between 
the  adjacent  lobules,  are  the 
"interlobular"  veins.  In  the 
spaces  between  the  lobules 
we  also  find  the  minute 
branches  of  the  hepatic  ar- 
tery, and  the  commencing 
rootlets  of  the  hepatic  ducts. 
As  the  portal  vein,  the  he- 
patic artery,  and  the  hepatic 
duct  enter  the  liver  at  the 
transverse  fissure,  they  are 
closely  invested  by  a  fibrous 
sheath,  termed  Glisson's  capsule,  which  accompanies  them  in  their 
divisions  and  ramifications.  In  some  of  the  lower  animals,  as  in  the 
pig,  this  sheath  extends  even  to  the  interlobular  spaces,  inclosing 
each  lobule  in  a  thin  fibrous  investment,  by  which  it  is  distinctly 
separated  from  the  neighboring  parts.  In  the  human  subject,  how- 
ever, Glisson's  capsule  becomes  gradually  thinner  as  it  penetrates 
the  liver,  and  disappears  altogether  before  reaching  the  interlobular 
spaces ;  so  that  here  the  lobules  are  nearly  in  contact  with  each 


Ramification  of  Portal  Vein  in  Liver. — a. 
Twig  of  portal  veiu.  d,  6.  Interlobular  veius.  c.  Acini. 


SECRETION    OF    THE    BILE.  339 

Other  by  tlieir  adjacent  surfaces,  being  separated  on]j  by  the  inter- 
lobular veins  and  the  minute  branches  of  the  hepatic  artery  and 
duct  previously  mentioned. 

From  the  sides  of  the  interlobular  veins,  and  also  from  their 
terminal  extremities,  there  are  given  off  capillary  vessels,  which 
penetrate  the  substance  of  each  lobule  and  converge  from  its  cir- 
cumference toward  its  centre,  inosculating  at  the  same  time  freely 
with  each  other,  so  as  to  form  a  minute  vascular  plexus,  the  "lobu- 
lar" capillary  plexus.  (Fig.  109.)     At  the  centre  of  each  lobule,  the 

Fig.  109. 


LoBiTLE  OF  Liver,  showing  distributioa  of  bloodvessels  ;  magnified  22  diameters —a.  fl-  la- 
terlobular  veins.  6.  Intralobular  vein,  c,  c,  c.  Lobular  capillary  plexus,  d,  d.  Twigs  of  inter- 
lobular vein  passing  to  adjacent  lobules. 

converging  capillaries  unite  into  a  small  vein  {h),  the  "  intralobu- 
lar" vein,  which  is  one  of  the  commencing  rootlets  of  the  hepatic 
vein.  These  rootlets,  uniting  successively  with  each  other,  so  as 
to  form  larger  and  larger  branches,  finally  leave  the  liver  at  its 
posterior  edge,  to  empty  into  the  ascending  vena  cava. 

Beside  the  capillary  bloodvessels  of  the  lobular  plexus,  each 
acinus  is  made  up  of  an  abundance  of  minute  cellular  bodies,  about 
tsVtt  of  an  inch  in  diameter,  the  "hepatic  cells."  (Fig.  110.)  These 
cells  have  an  irregularly  pentagonal  figure,  and  a  soft  consistency. 
They  are  composed  of  a  homogeneous  organic  substance,  in  the 
midst  of  which  are  imbedded  a  large  number  of  minute  granules, 
and  generally  several  well  defined  oil-globules.  There  is  also  a 
round  or  oval  nucleus,  with  a  nucleolus,  imbedded  in  the  substance 


340 


SECRETION. 


of  the  cell,  sometimes  more  or  less  obscured  by  tbe  granules  and 
oil  drops  with  which  it  is  surrounded. 

The  exact  mode  in  which  these  cells  are  connected  with  the 
hepatic  duct  was  for  a  long  time  the  most  obscure  point  in  the 

minute  anatomy  of  the  liver. 
^^'      '  It  has  now  been  ascertained, 

however,  by  the  researches  of 
Dr.  Leidy,  of  Philadelphia/ 
and  Dr.  Beale,  of  London,' 
that  they  are  really  contained 
in  the  interior  of  secreting 
tubules,  which  pass  off  from 
the  smaller  hepatic  ducts,  and 
penetrate  everywhere  the 
substance  of  the  lobules. 
The  cells  fill  nearly  or  com- 
pletely the  whole  cavity  of 
the  tubules,  and  the  tubules, 
themselves  lie  in  close  proxi- 
mity with  each  other,  so  as 
to  leave  no  space  between  them  except  that  which  is  occupied  by 
the  capillary  bloodvessels  of  the  lobular  plexus. 

These  cells  are  the  active  agents  in  accomplishing  the  function  of 
the  liver.  It  is  by  their  influence  that  the  blood  which  is  brought 
in  contact  with  them  suffers  certain  changes  which  give  rise  to  the 
secreted  products  of  the  organ.  The  ingredients  of  the  bile  first 
make  their  appearance  in  the  substance  of  the  cells.  They  are 
then  transuded  from  one  to  the  other,  until  they  are  at  last  dis- 
charged into  the  small  biliary  ducts  seated  in  the  interlobular 
spaces.  Bach  lobule  of  the  liver  must  accordingly  be  regarded  as 
a  mass  of  secreting  tubules,  lined  with  glandular  cells,  and  invested 
with  a  close  network  of  capillary  bloodvessels.  It  follows,  there- 
fore, from  the  abundant  inosculation  of  the  lobular  capillaries,  and 
the  manner  in  which  they  are  entangled  with  the  hepatic  tissue, 
that  the  blood,  in  passing  through  the  circulation  of  the  liver, 
comes  into  the  most  intimate  relation  with  the  glandular  cells  of 
the  organ,  and  gives  up  to  them  the  nutritious  materials  which  are 
afterward  converted  into  the  ingredients  of  the  bile. 


Hepatic   Cells.    From  the  human  subject. 


'  American  Journal  Med.  Sci.,  January,  1848. 

2  On  Some  Points  in  the  Minute  Anatomy  of  the  Liver.     London,  1856. 


EXCRETION.  341 


CHAPTER   XVII. 

EXCEETION. 

We  have  now  come  to  tlie  last  division  of  the  great  nutritive 
function,  viz.,  the  process  of  excretion.  In  order  to  understand  fairly 
the  nature  of  this  process  we  must  remember  that  all  the  component 
parts  of  a  living  organism  are  necessarily  in  a  state  of  constant 
change.  It  is  one  of  the  essential  conditions  of  their  existence  and 
activity  that  they  should  go  through  with  this  incessant  transforma- 
tion and  renewal  of  their  component  substances.  Every  living 
animal  and  vegetable,  therefore,  constantly  absorbs  certain  materials 
from  the  exterior,  which  are  modified  and  assimilated  by  the  pro- 
cess of  nutrition,  and  converted  into  the  natural  ingredients  of  the 
organized  tissues.  But  at  the  same  time  with  this  incessant  growth 
and  supply,  there  goes  on  in  the  same  tissues  an  equally  incessant 
process  of  waste  and  decomposition.  For  though  the  elements  of 
the  food  are  absorbed  by  the  tissues,  and  converted  into  musculine, 
osteine,  h83matine  and  the  like,  they  do  not  remain  permanently  in 
this  condition,  but  almost  immediately  begin  to  pass  over,  by  a  con- 
tinuance of  the  alterative  process,  into  new  forms  and  combinations, 
which  are  destined  to  be  expelled  from  the  body,  as  others  continue 
to  be  absorbed.  Thus  Spallanzani  and  Edwards  found  that  every 
organized  tissue  not  only  absorbs  oxygen  from  the  atmosphere 
and  fixes  it  in  its  own  substance;  but  at  the  same  time  exhales 
carbonic  acid,  which  has  been  produced  by  internal  metamorphosis. 
This  process,  by  which  the  ingredients  of  the  organic  tissues,  al- 
ready formed,  are  decomposed  and  converted  into  new  substances, 
is  called  the  process  of  Destructive  Assimilation. 

Accordingly  we  find  that  certain  substances  are  constantly  mak- 
ing their  appearance  in  the  tissues  and  fluids  of  the  body,  which 
did  not  exist  there  originally,  and  which  have  not  been  introduced 
with  the  food,  but  which  have  been  produced  by  the  process  of  in- 
ternal metamorphosis.  These  substances  represent  the  waste,  or 
physiological  detritus  of  the  animal  organism.     They  are  the  forms 


342  EXCRETION. 

under  wliicli  those  materials  present  themselves,  which  have  once 
formed  a  part  of  the  living  tissues,  but  which  have  become  altered 
by  the  incessant  changes  characteristic  of  organized  bodies,  and 
which  are  consequently  no  longer  capable  of  exhibiting  vital  pro- 
perties, or  of  performing  the  vital  functions.  They  are,  therefore, 
destined  to  be  removed  and  discharged  from  the  animal  frame,  and 
are  known  accordingly  by  the  name  of  Excrementitious  Substances. 

These  excrementitious  substances  have  peculiar  characters  by 
which  they  may  be  distinguished  from  the  other  ingredients  of  the 
living  body ;  and  they  might,  therefore,  be  made  to  constitute  a 
fourth  class  of  proximate  principles,  in  addition  to  the  three  which 
we  have  enumerated  in  the  preceding  chapters.  They- are  all  sub- 
stances of  definite  chemical  composition,  and  all  susceptible  of 
crystallization.  Some  of  the  most  important  of  them  contain  nitro- 
gen, while  a  few  are  non-nitrogenous  in  their  composition.  They 
originate  in  the  interior  of  living  bodies,  and  are  not  found  else- 
where, except  occasionally  as  the  result  of  decomposition.  They 
are  nearly  all  soluble  in  water,  and  are  soluble  without  exception  in 
the  animal  fluids.  They  are  formed  in  the  substance  of  the  tissues, 
from  which  they  are  absorbed  by  the  blood,  to  be  afterward  conveyed 
by  the  circulating  fluid  to  certain  excretory  organs,  particularly  the 
kidneys,  from  which  they  are  finally  discharged  and  expelled  from 
the  body.  This  entire  process,  made  up  of  the  production  of  the 
excrementitious  substances,  their  absorption  by  the  blood,  and  their 
final  elimination,  is  known  as  the  process  of  excretion. 

The  importance  of  this  process  to  the  maintenance  of  life  is  readily 
shown  by  the  injurious  effects  which  follow  upon  its  disturbance. 
If  the  discharge  of  the  excrementitious  substances  be  in  any  way 
impeded  or  suspended,  these  substances  accumulate,  either  in  the 
blood  or  in  the  tissues,  or  in  both.  In  consequence  of  this  retention 
and  accumulation,  they  become  poisonous,  and  rapidly  produce  a 
derangement  of  the  vital  functions.  Their  influence  is  principally 
exerted  upon  the  nervous  system,  through  which  they  produce 
most  frequent  irritability,  disturbance  of  the  special  senses,  deli- 
rium, insensibility,  coma,  and  finally  death.  The  readiness  with 
which  these  effects  are  produced  depends  on  the  character  of  the 
excrementitious  substance,  and  the  rapidity  with  which  it  is  pro- 
duced in  the  body.  Thus,  if  the  elimination  of  carbonic  acid  be 
stopped,  by  overloading  the  atmosphere  with  an  abundance  of  the 
same  gas,  death  takes  place  at  the  end  of  a  few  minutes ;  but  if  the 
elimination  of  urea  by  the  kidneys  be  checked,  it  requires  three  or 


UREA. 


343 


four  days  to  produce  a  fatal  result.  A  fatal  result,  however,  is  cer- 
tain to  follow,  at  the  end  of  a  longer  or  shorter  time,  if  any  one  of 
these  substances  be  compelled  to  remain  in  the  body,  and  accumu- 
late in  the  animal  tissues  and  fluids. 

The  principal  excrementitious  substances  known  to  exist  in  the 
human  body  are  as  follows : — 


1. 

Carbonic  acid     .... 

CO2 

2. 
3. 
4. 

Urea  ...... 

Creatine 

Creatinine           .... 

C,H,NA 

CgH.NaO^ 

5. 
6. 

7. 

Urate  of  soda     '.         .         .         . 
Urate  of  potassa         .         .         .         . 
Urate  of  ammonia      .         .         .         . 

NaO.C^HN^Oa+HO 

KO.CjHN^O^ 
NH,0,2C3HN202+HO 

The  physiological  relations  of  carbonic  acid  have  already  been 
studied,  at  sufficient  length,  in  the  preceding  chapters. 

The  remaining  excrementitious  substances  may  be  examined 
together  with  the  more  propriety,  since  they  are  all  ingredients  of 
a  single  excretory  fluid,  viz.,  the  urine. 


Urea. — This  is  a  neutral,  crystallizable,  nitrogenous  substance, 
very  readily  soluble  in  water,  and  easily  decomposed  by  various 
external  influences.  It  occurs 
in  the  urine  in  the  proportion 
of  30  parts  per  thousand;  in 
the  blood,  according  to  Picard,^ 
in  the  proportion  of  0.16  per 
thousand.  The  blood,  how- 
ever, is  the  source  from  which 
this  substance  is  supplied  to 
the  urine;  and  it  exists,  ac- 
cordingly, in  but  small  quan- 
tity in  the  circulating  fluid,  for 
the  reason  that  it  is  constantly 
drained  off  by  the  kidneys. 
But  if  the  kidneys  be  extir- 
pated, or  the  renal  arteries  tied, 
or  the  excretion  of  urine  sus- 
pended by  inflammation  or  otherwise,  the  urea  then  accumulates  in 
the  blood,  and  presents  itself  there  in  considerable  quantity.  It  has 
been  found  in  the  blood,  under  these  circumstances,  in  the  propor- 


Ure  A,  prepared  from  urine,  and  crystallized  by 
slow  evaporation.     (After  Lehmann.) 


'  In  Milne  Edwards,  Le9ons  sur  la  Physiologie,  &c.,  vol.  i.  p.  297. 


844  EXCRETION. 

tion  of  1.4  per  thousand.^  It  is  not  yet  known  from  wliat  source 
the  urea  is  originally  derived ;  whether  it  be  produced  in  the  blood 
itself;  or  whether  it  is  formed  in  some  of  the  solid  tissues,  and  thence 
taken  up  by  the  blood.  It  has  not  yet  been  found,  however,  in  any 
of  the  solid  tissues,  in  a  state  of  health. 

Urea  is  obtained  most  readily  from  the  urine.  For  this  purpose 
the  fresh  urine  is  evaporated  in  the  water  bath  until  it  has  a  syrupy 
consistency.  It  is  then  mixed  with  an  equal  volume  of  nitric  acid, 
which  forms  nitrate  of  urea.  This  salt,  being  less  soluble  than  pure 
urea,  rapidly  crystallizes,  after  which  it  is  separated  by  filtration 
from  the  other  ingredients.  It  is  then  dissolved  in  water  and  decom- 
posed by  carbonate  of  lead,  forming  nitrate  of  lead  which  remains 
in  solution,  and  carbonic  acid  which  escapes.  The  solution  is  then 
evaporated,  the  urea  dissolved  out  by  alcohol,  and  finally  crystal- 
lized in  a  pure  state. 

Urea  has  no  tendency  to  spontaneous  decomposition,  and  may 
be  kept,  when  perfectly  pure,  in  a  dry  state  or  dissolved  in  water, 
for  an  indefinite  length  of  time.  If  the  watery  solution  be  boiled, 
however,  the  urea  is  converted,  during  the  process  of  ebullition, 
into  carbonate  of  ammonia.  One  equivalent  of  urea  unites  with 
two  equivalents  of  water,  and  becomes  transformed  into  two  equiva- 
lents of  carbonate  of  ammonia,  as  follows : — 

C2H4N202=Urea.  NH3,C02=:Carbonate  of  ammonia. 

H,    0„=Water.  2 


C2H6N2O4  N2HeC20, 

Various  impurities,  also,  by  acting  as  catalytic  bodies,  will  in- 
duce the  same  change,  if  water  be  present.  Animal  substances  in 
a  state  of  commencing  decomposition  are  particularly  liable  to  act 
in  this  way.  In  order  that  the  conversion  of  the  urea  be  thus  pro- 
duced, it  is  necessary  that  the  temperature  of  the  mixture  be  not 
far  from  70°  to  100°  F. 

The  quantity  of  urea  produced  and  discharged  daily  by  a  healthy 
adult  is,  according  to  the  experiments  of  Lehmann,  about  500 
grains.  It  varies  to  some  extent,  like  all  the  other  secreted  and 
excreted  products,  with  the  size  and  development  of  the  body. 
Lehmann,  in  experiments  on  his  own  person,  found  the  average 
daily  quantity  to  be  487  grains.  Prof.  William  A.  Hammond,^ 
who  is  a  very  large  man,  by  similar  experiments  found  it  to  be 

'  Robin  and  Verdeil,  vol.  ii.  p.  502. 

^  American  Journal  Med.  Sci  ,  Jan.,  1855,  and  April,  1856. 


UREA.  345 

670  grains.  Dr.  John  C.  Draper'  found  it  408  grains.  No  urea  is 
to  be  detected  in  tlie  urine  of  very  young  children  f  but  it  soon 
makes  its  appearance,  and  afterward  increases  in  quantity  with  the 
development  of  the  body. 

The  daily  quantity  of  urea  varies  also  with  the  degree  of  mental 
and  bodily  activity.  Lehmann  and  Hammond  both  found  it  very 
sensibly  increased  by  muscular  exertion  and  diminished  by  repose. 
It  has  been  thought,  from  these  facts,  that  this  substance  must  be 
directly  produced  from  disintegration  of  the  muscular  tissue.  This, 
however,  is  by  no  means  certain ;  since  in  a  state  of  general  bodily 
activity  it  is  not  only  the  urea,  but  the  excretions  generally,  carbonic 
acid,  perspiration,  &c.,  which  are  increased  in  quantity  simultane- 
ously. Hammond  has  also  shown  that  continued  mental  applica- 
tion will  raise  the  quantity  of  urea  above  its  normal  standard, 
though  the  muscular  system  remain  comparatively  inactive. 

The  quantity  of  urea  varies  also  with  the  nature  of  the  food. 
Lehmann,  by  experiments  on  his  own  person,  found  that  the  quan- 
tity was  larger  while  living  exclusively  on  animal  food  than  with 
a  mixed  or  vegetable  diet ;  and  that  its  quantity  was  smallest  when 
confined  to  a  diet  of  purely  non-nitrogenous  substances,  as  starch, 
sugar,  and  oil.  The  following  table^  gives  the  result  of  these  ex- 
periments. 

Kind  op  Pood.  Daily  Quantity  op  Ukea, 

Animal 798  grains. 

Mixed 487      " 

Vegetable 337      " 

Non-nitrogenous 231      " 

Finally,  it  has  been  shown  by  Dr.  John  C.  Draper^  that  there  is 
also  a  diurnal  variation  in  the  normal  quantity  of  urea.  A  smaller 
quantity  is  produced  during  the  night  than  during  the  day ;  and 
this  difference  exists  even  in  patients  who  are  confined  to  the  bed 
during  the  whole  twenty-four  hours,  as  in  the  case  of  a  man  under 
treatment  for  fracture  of  the  leg.  This  is  probably  owing  to  the 
greater  activity,  during  the  waking  hours,  of  both  the  mental  and 
digestive  functions.  More  urea  is  produced  in  the  latter  half  than 
in  the  earlier  half  of  the  day ;  and  the  greatest  quantity  is  dis- 
charged during  the  four  hours  from  6|  to  10|  P.  M. 

Urea  exists  in  the  urine  of  the  carnivorous  and  many  of  the 

'  Nf^w  York  Journal  of  Medicine,  March,  1856. 

*  Robin  and  Verdnil,  vol.  ii.  p.  500. 

'  Lehmann,  op.  cit.,  vol.  ii.  p.  lUS.  *  Loc.  cit. 


346 


EXCRETIOlsr. 


herbivorous  quadrupeds ;  but  there  is  little  or  none  to  be  found  in 
that  of  birds  and  reptiles. 


Creatine,  crystallized  from  hot  water.   (After 
Lebmaan.) 


Creatine. — This  is  a  neutral  crystallizable  substance,  found  in 
the  muscleS;  the  blood,  and  the  urine.     It  is  soluble  in  water,  very 

slightly  soluble  in  alcohol,  and 
Fig- 112.  not  at  all  so  in  ether.     By  boil- 

ing with  an  alkali,  it  is  either 
converted  into  carbonic  acid 
and  ammonia,  or  is  decomposed 
with  the  production  of  urea  and 
an  artificial  nitrogenous  crys- 
tallizable substance,  termed  sar- 
cosine.  By  being  heated  with 
strong  acids,  it  loses  two  equiva- 
lents of  water,  and  is  converted 
into  the  substance  next  to  be 
described,  viz.,  creatinine. 

Ci'eatine  exists  in  the  urine, 
in  the  human  subject,  in  the 
proportion  of  about  1.25  parts, 
and  in  the  muscles  in  the  proportion  of  0.67  parts  per  thousand. 
Its  quantity  in  the  blood  has  not  been  determined.  In  the  muscu- 
lar tissue  it  is  simply  in  solution  in  the  interstitial  fluid  of  the  parts, 
so  that  it  may  be  extracted  by  sirnply  cutting  the  muscle  into 
small  pieces,  treating  it  with  distilled  water,  and  subjecting  it  to 

pressure.     Creatine    evidently 
Fig- 113.  originates  in  the  muscular  tis- 

sue, is  absorbed  thence  by  the 
blood,  and  is  finally  discharged 
with  the  urine. 


Creatinine. — This  is  also  a 
crystallizable  substance.  It  dif- 
fers in  composition  from  crea- 
tine by  containing  two  equiva- 
lents less  of  the  elements  of 
water.  It  is  more  soluble  in 
water  and  in  spirit  than  crea- 
tine, and  dissolves  slightly  also 
in  ether.      It   has  a  distinctly 


Creatinine, 
(After  Lehmann.) 


crystallized  from    hot  water. 


CREATININE. —  URATE    OE    SODA. 


347 


alkaline  reaction.  It  occurs,  like  creatine,  in  the  muscles,  the  blood, 
and  the  urine ;  and  is  undoubtedly  first  produced  in  the  muscular 
tissue,  to  be  discharged  finally  by  the  kidneys.  It  is  very  possible 
that  it  originates,  not  directly  from  the  muscles,  but  indirectly,  by 
transformation  of  a  part  of  the  creatine ;  since  it  may  be  artificially 
produced,  as  we  have  already  mentioned,  by  transformation  of  the 
latter  substance  under  the  influence  of  strong  acids,  and  since,  fur- 
thermore, while  creatine  is  more  abundant  in  the  muscles  than 
creatinine,  in  the  urine,  on  the  contrary,  there  is  a  larger  quantity 
of  creatinine  than  of  creatine.  Both  these  substances  have  been 
found  in  the  muscles  and  in  the  urine  of  the  lower  animals. 


Urate  of  Soda.— As  its  name  implies,  this  substance  is  a  neu- 
tral salt,  formed  by  the  union  of  soda,  as  a  base,  with  a  nitrogenous 
animal  acid,  viz.,  uric  acid  (CjHNgOgjHO).  Uric  acid  is  sometimes 
spoken  of  as  though  it  were  itself  a  proximate  principle,  and  a 
constituent  of  the  urine;  but  it  cannot  properly  be  regarded  as 
such,  since  it  never  occurs  in  a  free  state,  in  a  natural  condition  of 
the  fluids.  When  present,  it  has  always  been  produced  by  decom- 
position of  the  urate  of  soda. 

Urate  of  soda  is  readily  soluble  in  hot  water,  from  which  a  large 
portion  again  deposits  on  cooling.  It  is  slightly  soluble  in  alcohol, 
and  insoluble  in   ether.     It 

crystallizes  in  small  globu-  Fig-  314. 

lar  masses,  with  projecting, 
curved,  conical,  wart-like 
excrescences.  (Fig.  114.)  It 
dissolves  readily  in  the  alka- 
lies ;  and  by  most  acid  solu- 
tions it  is  decomposed,  with 
the  production  of  free  uric 
acid. 

Urate  of  soda  exists  in 
the  urine  and  in  the  blood. 
It  is  either  produced  origin- 
ally in  the  blood,  or  is  formed 
in  some  of  the  solid  tissues, 
and  absorbed  from  them  by 
the  circulating  fluid.     It  is 

constantly  eliminated  by  the  kidneys,  in  company  with  the  other 
ingredients  of  the  urine.     The  average  daily  quantity  of  urate  of 


Urate   of   Soda;  from  a  urinary  deposit. 


348  EXCRETION. 

soda  discharged  by  the  healthy  human  subject  is,  according  to 
Lehmann,  about  25  grains.  This  substance  exists  in  the  urine  of 
the  carnivorous  and  omnivorous  animals,  but  not  in  that  of  the  her- 
bivora.  In  the  latter,  it  is  replaced  by  another  substance,  differing 
somewhat  from  it  in  composition  and  properties,  viz.,  hippurate 
of  soda.  The  urine  of  herbivora,  however,  while  still  very  young, 
and  living  upon  the  milk  of  the  mother,  has  been  found  to  contain 
urates.  But  when  the  young  animal  is  weaned,  and  becomes  her- 
bivorous, the  urate  of  soda  disappears,  and  is  replaced  by  the  hip- 
purate. 

Urates  of  Potass  a  and  Ammonia. — The  urates  of  potassa  and 
ammonia  resemble  the  preceding  salt  very  closely  in  their  physio- 
logical relations.  They  are  formed  in  very  much  smaller  quantity 
than  the  urate  of  soda,  and  appear  like  it  as  ingredients  of  the  urine. 

The  substances  above  enumerated  closely  resemble  each  other  in 
their  most  striking  and  important  characters.  They  all  contain 
nitrogen,  are  all  cry  stall  izable,  and  all  readily  soluble  in  water. 
They  all  originate  in  the  interior  of  the  body  by  the  decomposition 
or  catalytic  transformation  of  its  organic  ingredients,  and  are  all 
conveyed  by  the  blood  to  the  kidneys,  to  be  finally  expelled  with 
the  urine.  These  are  the  substances  which  represent,  to  a  great 
extent,  the  final  transformation  of  the  organic  or  albuminoid  in- 
gredients of  the  tissues.  It  has  already  been  mentioned,  in  a  pre- 
vious chapter,  that  these  organic  or  albuminoid  substances  are  not 
discharged  from  the  body,  under  their  own  form,  in  quantity  at  all 
proportionate  to  the  abundance  with  which  they  are  introduced. 
By  far  the  greater  part  of  the  mass  of  the  frame  is  made  up  of 
organic  substances:  albumen,  musculine,  osteine,  &c.  Similar 
materials  are  taken  daily  in  large  quantity  with  the  food,  in  order 
to  supply  the  nutrition  and  waste  of  those  already  composing  the 
tissues ;  and  yet  only  a  very  insignificant  quantity  of  similar 
material  is  expelled  with  the  excretions.  A  minute  proportion  of 
volatile  animal  matter  is  exhaled  with  the  breath,  and  a  minute 
proportion  also  with  the  perspiration.  A  very  small  quantity  is 
discharged  under  the  form  of  mucus  and  coloring  matter,  with  the 
urine  and  feces ;  but  all  these  taken  together  are  entirely  insuffi- 
cient to  account  for  the  constant  and  rapid  disappearance  of  organic 
matters  in  the  interior  of  the  body.  These  matters,  in  fact,  before 
being  discharged,  are  converted  by  catalysis  and  decomposition  into 
new  substances.     Carbonic  acid,  under  which  form  3500  grains  of 


GENERAL    CHARACTERS    OF    THE    URINE.  349 

carbon  are  daily  expelled  from  the  body,  is  one  of  these  substances ; 
the  others  are  urea,  creatine,  creatinine,  and  the  urates. 

We  see,  then,  in  what  way  the  organic  matters,  in  ceasing  to  form 
a  part  of  the  living  body,  lose  their  characteristic  properties,  and 
are  converted  into  crystallizable  substances,  of  definite  chemical 
composition.  It  is  a  kind  of  retrograde  metamorphosis,  by  which 
they  return  more  or  less  to  the  condition  of  ordinary  inorganic 
materials.  These  excrementitious  matters  are  themselves  decom- 
posed, after  being  expelled  from  the  body,  under  the  influence  of 
the  atmospheric  air  and  moisture ;  so  that  the  decomposition  and 
destruction  of  the  organic  substances  are  at  last  complete. 

It  will  be  seen,  consequently,  that  the  urine  has  a  character 
altogether  peculiar,  and  one  which  distinguishes  it  completely 
from  every  other  animal  fluid.  All  the  others  are  either  nutritive 
fluids,  like  the  blood  and  milk,  or  are  destined,  like  the  secretions 
generally,  to  take  some  direct  and  essential  part  in  the  vital  opera- 
tions. Many  of  them,  like  the  gastric  and  pancreatic  juices,  are 
reabsorbed  after  they  have  done  their  work,  and  again  enter  the 
current  of  the  circulation.  But  the  urine  is  merely  a  solution  of 
excrementitious  substances.  Its  materials  exist  beforehand  in  the 
circulation,  and  are  simply  drained  away  by  the  kidneys  from 
the  blood.  There  is  a  wide  difference,  accordingly,  between  the 
action  of  the  kidneys  and  that  of  the  true  glandular  organs,  in 
which  certain  new  and  peculiar  substances  are  produced  by  the 
action  of  the  glandular  tissue.  The  kidneys,  on  the  contrary,  do 
not  secrete  anything,  properly  speaking,  and  are  not,  therefore, 
glands.  In  their  mode  of  action,  so  far  as  regards  the  excretory 
function,  they  have  more  resemblance  to  the  lungs  than  to  any 
other  of  the  internal  organs.  But  this  resemblance  is  not  complete ; 
since  the  lungs  perform  a  double  function,  absorbing  oxygen  at  the 
same  time  that  they  exhale  carbonic  acid.  The  kidneys  alone  are 
purely  excretory  in  their  office.  The  urine  is  not  intended  to 
fulfil  any  function,  mechanical,  chemical,  or  otherwise ;  but  is  des- 
tined only  to  be  eliminated  and  expelled.  Since  it  possesses  so 
peculiar  and  important  a  character,  it  will  require  to  be  carefully 
studied  in  detail. 

The  urine  is  a  clear,  watery,  amber-colored  fluid,  with  a  distinct 
acid  reaction.  It  has,  while  still  warm,  a  peculiar  odor,  which  dis- 
appears more  or  less  completely  on  cooling,  and  returns  when  the 
urine  is  gently  heated.  The  ordinary  quantity  of  urine  discharged 
daily  by  a  healthy  adult  is  about  sxxxv,  and  its  mean  specific 


850  EXCRETION, 

gravity,  1024.  Botli  its  total  quantity,  however,  and  its  mean 
specific  gravity  are  liable  to  vary  somewliat  from  day  to  day,  owing 
to  the  difibrent  proportions  of  water  and  solid  ingredients  entering 
into  its  constitution.  Ordinarily  the  water  of  the  urine  is  more 
than  sufficient  to  hold  all  the  solid  matters  in  solution ;  and  its  pro- 
portion may  therefore  be  diminished  by  accidental  causes  without 
the  urine  becoming  turbid  by  the  formation  of  a  deposit.  Under 
such  circumstances,  it  merely  becomes  deeper  in  color,  and  of  a 
higher  specific  gravity.  Thus,  if  a  smaller  quantity  of  water  than 
usual  be  taken  into  the  system  with  the  drink,  or  if  the  fluid  ex- 
halations from  the  lungs  and  skin,  or  the  intestinal  discharges,  be 
increased,  a  smaller  quantity  of  water  will  necessarily  pass  off  by 
the  kidneys ;  and  the  urine  will  be  diminished  in  quantity,  while  its 
specific  gravity  is  increased.  We  have  observed  the  urine  to  be 
reduced  in  this  way  to  eighteen  or  twenty  ounces  per  day,  its  specific 
gravity  rising  at  the  same  time  to  1030.  On  the  other  hand,  if  the 
fluid  ingesta  be  unusually  abundant,  or  if  the  perspiration  be  dimi- 
nished, the  surplus  quantity  of  water  will  pass  ofi'by  the  kidneys;  so 
that  the  amount  of  urine  in  twenty-four  hours  may  be  increased  to 
forty-five  or  forty-six  ounces,  and  its  specific  gravity  reduced  at 
the  same  time  to  1020  or  even  1017.  Under  these  conditions  the 
total  amount  of  solid  matter  discharged  daily  remains  about  the 
same.  The  changes  above  mentioned  depend  simply  upon  the 
fluctuating  quantity  of  water,  which  may  pass  off  by  the  kidneys 
in  larger  or  smaller  quantity,  according  to  accidental  circumstances. 
In  these  purely  normal  or  physiological  variations,  therefore,  the 
entire  quantity  of  the  urine  and  its  mean  specific  gravity  vary 
always  in  an  inverse  direction  with  regard  to  each  other ;  the  former 
increasing  while  the  latter  diminishes,  and  vice  versa.  If,  however,  it 
should  be  found  that  both  the  quantity  and  specific  gravity  of  the 
urine  were  increased  or  diminished  at  the  same  time,  or  if  either 
one  were  increased  or  diminished  while  the  other  remained  station- 
ary, such  an  alteration  would  show  an  actual  change  in  the  total 
amount  of  solid  ingredients,  and  would  indicate  an  unnatural  and 
pathological  condition.  This  actually  takes  place  in  certain  forms 
of  disease. 

The  amount  of  variation  in  the  quantity  of  water,  even,  may  be 
so  great  as  to  constitute  by  itself  a  pathological  condition.  Thus, 
in  hysterical  attacks  there  is  sometimes  a  very  abundant  flow  of 
limpid,  nearly  colorless  urine,  with  a  specific  gravity  not  over  1005 
or  1006.     On  the  other  hand,  in  the  onset  of  febrile  attacks,  the 


DIURNAL    VARIATIONS    OF    THE    URINE.  351 

quantity  of  water  is  often  so-  much,  diminished  that  it  is  no  longer 
sufficient  to  retain  in  solution  all  the  solid  ingredients  of  the  urine, 
and  the  urate  of  soda  is  thrown  down,  after  cooling,  as  a  fine  red 
or  yellowish  sediment.  -So  long,  however,  as  the  variation  is  con- 
fined within  strictly  physiological  limits,  all  the  solid  ingredients 
are  held  in  solution,  and  the  urine  remains  clear. 

There  is  also,  in  a  state  of  health,  a  diurnal  variation  of  the  urine, 
both  in  regard  to  its  specific  gravity  and  its  degree  of  acidity. 
The  urine  is  generally  discharged  from  the  bladder  five  or  six 
times  during  the  twenty-four  hours,  and  at  each  of  these  periods 
shows  more  or  less  variation  in  its  physical  characters.  We  have 
found  that  the  urine  which  collects  in  the  bladder  during  the 
night,  and  is  first  discharged  in  the  morning,  is  usually  dense, 
highly  colored,  of  a  strongly  acid  reaction,  and  a  high  specific 
gravity.  That  passed  during  the  forenoon  is  pale,  and  of  a  low 
specific  gravity,  sometimes  not  more  than  1018  or  even  1015,  It 
is  at  the  same  time  neutral  or  slightly  alkaline  in  reaction.  Toward 
the  middle  of  the  day,  its  density  and  depth  of  color  increase,  and 
its  acidity  returns.  All.  these  properties  become  more  strongly 
marked  during  the  afternoon  and  evening,  and  toward  night  the 
urine  is  again  deeply  colored  and  strongly  acid,  and  has  a  specific 
gravity  of  1028  or  1030. 

The  following  instances  will  serve  to  show  the  general  characters* 
of  this  variation : — 

Observation  Fihst.     March  20t'h. 
Urine  of  1st  discharge,  acid,         sp.  gr.  1025. 
"     2d  "  alkaline,       "       1015. 

"     3d  "  neutral,         "       1018. 

"     4th        "  acid,  "       1018. 

"     5th        "  acid,  "      1027. 

Observation  Second.     March  2\st. 
Urine  of  1st  discharge,  acid,  sp.  gr.  1029. 

"     2d  "  neutral,         "       1022. 

"     3d  "  neutral,         «       1025. 

"     4th        "  acid,  "       1027. 

"     5th        "  acid,  "       1030. 

These  variations  do  not  always  follow  the  perfectly  regular 
course  manifested  in  the  above  instances,  since  they  are  somewhat 
liable,  as  we  have  already  mentioned,  to  temporary  modification 
from  accidental  causes  during  the  day ;  but  their  general  tendency 
nearly  always  corresponds  with  that  given  above. 

It  is  evident,  therefore,  that  whenever  we  wish  to  test  the  sDecific 


852  EXCRETION. 

gravity  and  acidity  of  the  urine  in  cases  of  disease,  it  will  not  be 
sufficient  to  examine  any  single  specimen  taken  at  random ;  but  all 
tbe  different  portions  discharged  during  the  day  should  be  collected 
and  examined  together.  Otherwise,  we  should  incur  the  risk  of 
regarding  as  a  permanently  morbid  symptom  what  might  be 
nothing  more  than  a  purely  accidental  and  temporary  variation. 

The  chemical  constitution  of  the  urine  as  it  is  discharged  from  the 
bladder,  according  to  the  analyses  of  Berzelius,  Lehmann,  Becquerel, 
and  others,  is  as  follows : — 

Composition  of  the  XJkike. 

Water 938.00 

Urea 30.00 

Creatine 1.25 

Creatinine 1.50 

Urate  of  soda         -v 

"     potassa     \ 1.80 

"     ammonia  J 
Coloring  matter  and  1  oq 

Mucus  y 

Biphosphate  of  soda 
Phosphate  of  soda 

"  potassa       • 12.45 

"  magnesia 

«  lime 

Chlorides  of  sodium  and  potassium 7.80 

Sulphates  of  soda  and  potassa 6.90 

1000.00 

"We  need  not  repeat  that  the  proportionate  quantity  of  these 
different  ingredients,  as  given  above,  is  not  absolute,  but  only 
approximative;  and  that  they  vary,  from  time  to  time,  within 
certain  physiological  limits,  like  the  ingredients  of  all  other  animal 
fluids. 

The  urea,  creatine,  creatinine  and  urates  have  all  been  suffi- 
ciently described  above.  The  mucus  and  coloring  matter,  unlike 
the  other  ingredients  of  the  urine,  belong  to  the  class  of  organic 
substances  proper.  They  are  both  present,  as  may  be  seen  by  the 
analysis  quoted  above,  in  a  very  small  quantity.  The  coloring 
matter,  or  urosacine,  is  in  solution  in  a  natural  condition  of  the 
urine,  but  it  is  apt  to  be  entangled  by  any  accidental  deposits  whicK 
may  be  thrown  down,  and  more  particularly  by  those  consisting  of 
the  urates.  These  deposits,  from  being  often  strongly  colored  red 
or  pink  by  the  urosacine  thus  thrown  down  with  them,  are  known 
under  the  name  of  "  brick-dust"  sediments. 

The  mucus  of  the  urine  comes  from  the  lining  membrane  of  the 


REACTIONS    OF    THE    URINE.  353 

urinary  bladder.  When  first  discharged  it  is  not  visible,  owing  to 
its  being  uniformly  disseminated  through  the  urine  by  mechanical 
agitation ;  but  if  the  fluid  be  allowed  to  remain  at  rest  for  some 
hours  in  a  cylindrical  glass  vessel,  the  mucus  collects  at  the  bottom, 
and  may  then  be  seen  as  a  light  cottony  cloud,  interspersed  often 
with  minute  semi-opaque  points.  It  plays,  as  we  shall  hereafter 
see,  a  very  important  part  in  the  subsequent  fermentation  and 
decomposition  of  the  urine. 

Biphosphate  of  soda  exists  in  the  urine  by  direct  solution,  since  it  is 
readily  soluble  in  water.  It  is  this  salt  which  gives  to  the  urine  its 
acid  reaction,  as  there  is  no  free  acid  present,  in  the  recent  condition. 
It  is  probably  derived  from  the  neutral  phosphate  of  soda  in  the 
blood  which  is  decomposed  by  the  uric  acid  at  the  time  of  its  form- 
ation ;  producing,  on  the  one  hand,  a  urate  of  soda,  and  converting 
a  part  of  the  neutral  phosphate  of  soda  into  the  acid  biphosphate. 

The  phosphates  of  lime  and  magnesia,  or  the  "  earthy  phosphates," 
as  they  are  called,  exist  in  the  urine  by  indirect  solution.  Though 
insoluble,  or  very  nearly  so,  in  pure  water,  they  are  held  in  solu- 
tion in  the  urine  by  the  acid  phosphate  of  soda,  above  described. 
They  are  derived  from  the  blood,  in  which  they  exist  in  considera- 
ble quantity.  When  the  urine  is  alkaline,  these  phosphates  are 
deposited  as  a  light-colored  precipitate,  and  thus  communicate  a 
turbid  appearance  to  the  fluid.  When  the  urine  is  neutral,  they 
may  still  be  held  in  solution,  to  some  extent,  by  the  chloride  of 
sodium,  which  has  the  property  of  dissolving  a  small  quantity  of 
phosphate  of  lime. 

The  remaining  ingredients,  phosphates  of  soda  and  potassa,  sul- 
phates and  chlorides,  are  all  derived  from  the  blood,  and  are  held 
directly  in  solution  by  the  water  of  the  urine." 

The  urine,  constituted  by  the  above  ingredients,  forms,  as  we 
have  already  described,  a  clear  amber-colored  fluid,  with  a  reaction 
for  the  most  part  distinctly  acid,  sometimes  neutral,  and  occasion- 
ally slightly  alkaline.  In  its  healthy  condition  it  is  affected  by 
chemical  and  physical  reagents  in  the  following  manner. 

Boiling  the  urine  does  not  produce  any  visible  change,  provided 
its  reaction  be  acid.  If  it  be  neutral  or  alkaline,  and  if,  at  the  same 
time,  it  contain  a  larger  quantity  than  usual  of  the  earthy  phos- 
phates, it  will  become  turbid  on  boiling;  since  these  salts  are  less 
soluble  at  a  high  than  at  a  low  temperature. 

The  addition  of  nitric  or  other  mineral  acid  produces  at  first  only 
23 


854 


EXCRETION. 


a  slight  darkening  of  the  color,  owing  to  the  action  of  the  acid  upon 
the  organic  coloring  matter  of  the  urine.  If  the  mixture;  however, 
be  allowed  to  stand  for  some  time,  the  urates  of  soda,  potassa,  &;c., 
will  be  decomposed,  and  pure  uric  acid,  which  is  very  insoluble, 
will  be  deposited  in  a  crystalline  form  upon  the  sides  and  bottom 
of  the  glass  vessel.  The  crystals  of  uric  acid  have  most  frequently 
the  form  of  transparent  rhomboidal  plates,  or  oval  laminse  with 
pointed  extremities.  They  are  usually  tinged  of  a  yellowish  hue 
by  the  coloring  matter  of  the  urine  which  is  united  with  them 
at  the  time  of  their  deposit.  They  are  frequently  arranged  in 
radiated  clusters,  or  small  spheroidal  masses,  so  as  to  present  the 

appearance  of  minute  calcu- 
Fig.  115-  lous  concretions.     (Fig.  115.) 

The  crystals  vary  very  much 
in  size  and  regularity,  ac- 
cording to  the  time  occupied 
in  their  formation. 

If  a  free  alkali,  such  as 
potassa  or  soda,  be  added  to 
the  urine  so  as  to  neutralize 
its  acid  reaction,  it  becomes 
immediately  turbid  from  a 
deposit  of  the  earthy  phos- 
phates, which  are  insoluble 
in  alkaline  fluids. 

The  addition  of  nitrate  of 
baryta,  chloride  of  barium 
or  subacetate  of  lead  to  healthy  urine,  produces  a  dense  precipi- 
tate, owing  to  the  presence  of  the  alSaline  sulphates. 

Nitrate  of  silver  produces  a  precipitate  with  the  chlorides  of 
sodium  and  potassium. 

Subacetate  of  lead  and  nitrate  of  silver  precipitate  also  the  or- 
ganic substances,  mucus  and  coloring  matter,  present  in  the  urine. 
All  the  above  reactions,  it  will  be  seen,  are  owing  to  the  presence 
of  the  natural  ingredients  of  the  urine,  and  do  not,  therefore,  indi- 
cate any  abnormal  condition  of  the  excretion. 

Beside  the  properties  mentioned  above,  the  urine  has  several 
others  which  are  of  some  importance,  and  which  have  not  been 
usually  noticed  in  previous  descriptions.  It  contains,  among  other 
ingredients,  certain  organic  substances  which  have  the  power  of 
interfering  with  the  mutual  reaction  of  starch  and  iodine,  and  even 


Uric  Acid  ;  deposited  li-oin  urine. 


REACTIONS    OF    THE    URINE.  355 

of  decomposing-  the  iodide  of  starch,  after  it  has  once  been  formed. 
This  peculiar  action  of  the  urine  was  first  noticed  and  described 
by  us  in  1856."  If  5j  of  iodine  water  be  mixed  with  a  solution 
of  starch,  it  strikes  an  opaque  blue  color ;  but  if  3j  of  fresh  urine 
be  afterward  added  to  the  mixture,  the  color  is  entirely  destroyed 
at  the  end  of  four  or  five  seconds.  If  fresh  urine  be  mixed  with 
four  or  five  times  its  volume  of  iodine  water,  and  starch  be 
subsequently  added,  no  union  takes  place  between  the  starch  and 
iodine,  and  no  blue  color  is  produced.  In  these  instances,  the  iodine 
unites  with  the  animal  matters  of  the  urine  in  preference  to  com- 
bining with  the  starch,  and  is  consequently  prevented  from  striking 
its  ordinary  blue  color  with  the  latter.  This  interference  occurs 
whether  the  urine  be  acid  or  alkaline  in  reaction.  In  all  cases  in 
which  iodine  exists  in  the  urine,  as  for  example  where  it  hatj  been 
administered  as  a  medicine,  it  is  under  the  form  of  an  organic  com- 
bination ;  and  in  order  to  detect  its  presence  by  means  of  starch,  a 
few  drops  of  nitric  acid  must  be  added  at  the  same  time,  so  as  to 
destroy  the  organic  matters,  after  which  the  blue  color  immediately 
appears,  if  iodine  be  present.  This  reaction  with  starch  and  iodine 
belongs  also,  to  some  extent,  to  most  of  the  other  animal  fluids,  as 
the  saliva,  gastric  and  pancreatic  juices,  serum  of  the  blood,  &c. ; 
but  it  is  most  strongly  marked  in  the  urine. 

Another  remarkable  property  of  the  urine,  also  dependent  on  its 
organic  ingredients,  is  that  of  interfering  with  Trommer's  test  for 
grape  sugar.  If  clarified  honey  be  mixed  with  fresh  urine,  and  sul- 
phate of  copper  with  an  excess  of  potassa  be  afterward  added,  the 
mixture  takes  a  dingy,  grayish-blue  color.  On  boiling,  the  color 
turns  yellowish  or  yellowish-brown,  but  the  suboxide  of  copper  is 
not  deposited.  In  order  to  remove  the  organic  matter  and  detect 
the  sugar,  the  urine  must  be  first  treated  with  an  excess  of  animal 
charcoal  and  filtered.  By  this  means  the  organic  substances  are 
retained  upon  the  filter,  while  the  sugar  passes  through  in  solution, 
and  may  then  be  detected  as  usual  by  Trommer's  test. 

Accidental  Ingredients  of  the  Urine. — Since  the  urine,  in 
its  natural  state,  consists  of  materials  which  are  already  prepared  in 
the  blood,  and  which  merely  pass  out  through  the  kidneys  by  a 
kind  of  filtration,  it  is  not  surprising  that  most  medicinal  and 
poisonous  substances,  introduced   into  the  circulation,  should   be 

'  American  Joamal  Med.  Sci.,  April,  1856. 


856  EXCRETIOIS". 

expelled  from  the  body  by  the  same  channel.  Those  substances 
which  tend  to  unite  strongly  with  the  animal  matters,  and  to  form 
with  them  insoluble  compounds,  such  as  the  preparations  of  iron, 
lead,  silver,  arsenic,  mercury,  &c,,  are  least  liable  to  appear  in  the 
urine.  They  may  occasionally  be  detected  in  this  fluid  when  they 
have  been  given  in  large  doses,  but  when  administered  in  moderate 
quantity  are  not  usually  to  be  found  there.  Most  other  substances, 
however,  accidentally  present  in  the  circulation,  pass  off  readily  by 
the  kidneys,  either  in  their  original  form,  or  after  undergoing  cer- 
tain chemical  modifications. 

The  salts  of  the  organic  acids,  such  as  lactates,  acetates,  malates, 
&c.,  of  soda  and  potassa,  when  introduced  into  the  circulation,  are 
replaced  by  the  carbonates  of  the  same  bases,  and  appear  under 
that  form  in  the  urine.  The  urine  accordingly  becomes  alkaline 
from  the  presence  of  the  carbonates,  whenever  the  above  salts  have 
been  taken  in  large  quautity,  or  after  the  ingestion  of  fruits  and 
vegetables  which  contain  them.  We  have  already  spoken  (Chap.  II.) 
of  the  experiments  of  Lehmann,  in  which  he  found  the  urine  exhi- 
bitino-  an  alkaline  reaction,  a  very  few  minutes  after  the  administra- 
tion of  lactates  and  acetates.  In  one  instance,  by  experimenting 
upon  a  person  with  congenital  extroversion  of  the  bladder,  in  whom 
the  orifices  of  the  ureters  were  exposed,^  he  found  that  the  urine 
became  alkaline  in  the  course  of  seven  minutes  after  the  ingestion 
of  half  an  ounce  of  acetate  of  potassa. 

The  jswre  alkalies  and  their  carbonates,  according  to  the  same  ob- 
server, produce  a  similar  effect.  Bicarbonate  of  potassa,  for  example, 
administered  in  doses  of  two  or  three  drachms,  causes  the  urine 
to  become  neutral  in  from  thirty  to  forty-five  minutes,  and  alkaline 
in  the  course  of  an  hour.  It  is  in  this  way  that  certain  "  anti-cal- 
culous"  or  "  anti-lithic"  nostrums  operate,  when  given  with  a  view 
of  dissolving  concretions  in  the  bladder.  These  remedies,  which 
are  usually  strongly  alkaline,  pass  into  the  urine,  and  by  giving  it 
an  alkaline  reaction,  produce  a  precipitation  of  the  earthy  phos- 
phates. Such  a  precipitate,  however,  so  far  from  indicating  the 
successful  disintegration  and  discharge  of  the  calculus,  can  only 
tend  to  increase  its  size  by  additional  deposit. 

Ferrocyanide  of  potassium,  when  introduced  into  the  circulation, 
appears  readily  in  the  urine.     Bernard^  observed  that  a  solution  of 

'  Pliysiological  Chemisty,  vol.  ii.  p.  133. 

^  Leqoiis  de  Physiologie  Experimentale,  1856,  p.  111. 


ACCIDENTAL    INGREDIENTS    OF    THE    URINE.  357 

this  salt,  after  being  injected  into  the  duct  of  the  submaxillary 
gland,  could  be  detected  in  the  urine  at  the  end  of  twenty  minutes. 

Iodine,  in  all  its  combinations,  passes  out  by  the  same  channel. 
We  have  found  that  after  the  administration  of  half  a  drachm  of 
the  syrup  of  iodide  of  iron,  iodine  appears  in  the  urine  at  the  end 
of  thirty  minutes,  and  continues  to  be  present  for  nearly  twenty- 
four  hours.  In  the  case  of  two  patients  who  had  been  taking  iodide 
of  potassium  freely,  one  of  them  for  two  months,  the  other  for  six 
weeks,  the  urine  still  contained  iodine  at  the  end  of  three  days 
after  the  suspension  of  the  medicine.  In  three  days  and  a  half, 
however,  it  was  no  longer  to  be  detected.  Iodine  appears  also, 
after  being  introduced  into  the  circulation,  both  in  the  saliva  and 
the  perspiration. 

Quinine,  when  taken  as  a  remedy,  has  also  been  detected  in  the 
urine.  Ether  passes  out  of  the  circulation  in  the  same  way.  We 
have  observed  the  odor  of  this  substance  very  perceptibly  in  the 
urine,  after  it  had  been  inhaled  for  the  purpose  of  producing  anaes- 
thesia. The  hile-pigm.ent  passes  into  the  urine  in  great  abundance 
in  some  cases  of  jaundice,  so  that  the  urine  may  have  a  deep  yellow 
or  yellowish  brown  tinge,  and  may  even  stain  linen  clothes,  with 
which  it  comes  in  contact,  of  a  similar  color.  The  saline  biliary 
substances,  viz.,  glyko-cholate  and  tauro-cholate  of  soda,  have  occa- 
sionally, according  to  Lehmann,  been  also  found  in  the  urine.  In 
these  instances  the  biliary  matters  are  reabsorbed  from  the.  hepatic 
ducts,  and  afterward  conveyed  by  the  blood  to  the  kidneys. 

Sugar. — When  sugar  exists  in  unnatural  quantity  in  the  blood, 
it  passes  out  with  the  urine.  We  have  repeatedly  found  that  if 
sugar  be  artificially  introduced  into  the  circulation  in  rabbits,  or 
injected  into  the  subcutaneous  areolar  tissue  so  as  to  be  absorbed  by 
the  blood,  it  is  soon  discharged  by  the  kidneys.  It  has  been  shown 
by  Bernard'  that  the  rapidity  with  which  this  substance  appears  in 
the  urine  under  these  circumstances  varies  with  the  quantity  in- 
jected and  the  kind  of  sugar  used  for  the  experiment.  If  a  solution 
of  15  grains  of  glucose  be  injected  into  the  areolar  tissue  of  a  rabbit 
weighing  a  little  over  two  pounds,  it  is  entirely  destroyed  in  the 
circulation,  and  does  not  pass  out  with  the  urine.  A  dose  of  23 
grains,  however,  injected  in  the  same  way,  appears  in  the  urine  at 
the  end  of  two  hours,  30  grains  in  an  hour  and  a  half,  38  grains  in 
an  hour,  and  188  grains  in  fifteen  minutes.     Again,  the  kind  of 

'  Le.ons  de  Phjs.  Exp.,  1855,  p.  214  et  seq. 


858  EXCEETION. 

sugar  used  makes  a  difference  in  this  respect.  For  while  15  grains 
of  glucose  may  be  injected  without  passing  out  by  the  kidneys, 
TJ  grains  of  cane  sugar,  introduced  in  the  same  way,  fail  to  be  com- 
pletely destroyed  in  the  circulation,  and  may  be  detected  in  the 
urine.  In  certain  forms  of  disease  (diabetes),  where  sugar  accu- 
mulates in  the  blood,  it  is  eliminated  by  the  same  channel ;  and  a 
saccharine  condition  of  the  nrine,  accompanied  by  an  increase  in 
its  quantity  and  specific  gravity,  constitutes  the  most  characteristic 
feature  of  the  disease. 

Finally,  albumen  sometimes  shows  itself  in  the  urine  in  conse- 
quence of  various  morbid  conditions.  Most  acute  inflammations 
of  the  internal  organs,  as  pneumonia,  pleurisy,  &c.,  are  liable  to  be 
accompanied,  at  their  outset,  by  a  congestion  of  the  kidneys,  which 
produces  a  temporary  exudation  of  the  albuminous  elements  of  the 
blood.  Albumen  has  been  found  in  the  urine,  according  to  Simon, 
Becquerel,  and  others,  in  pericarditis,  pneumonia,  pleurisy,  bron- 
chitis, hepatitis,  inflammation  of  the  brain,  peritonitis,  metritis,  &c. 
We  have  observed  it,  as  a  temporary  condition,  in  pneumonia  and 
after  amputation  of  the  thigh.  Albuminous  urine  also  occurs  fre- 
quently in  pregnant  women,  and  in  those  affected  with  abdominal 
tumors,  where  the  pressure  upon  the  renal  veins  is  sufficient  to 
produce  passive  congestion  of  the  kidneys.  When  the  renal  con- 
gestion is  spontaneous  in  its  origin,  and  goes  on  to  produce  actual 
degeneration  of  the  tissue  of  the  kidneys,  as  in  Bright's  disease,  the 
same  symptom  occurs,  and  remains  as  a  permanent  condition.  In 
all  such  instances,  however,  as  the  above,  where  foreign  ingredients 
exist  in  the  urine,  these  substances  do  not  originate  in  the  kidneys 
themselves,  but  are  derived  from  the  blood,  in  the  same  manner  as 
the  natural  ingredients  of  the  excretion. 

Changes  in  the  TJeine  dueing  Decomposition. — When  the 
urine  is  allowed  to  remain  exposed,  after  its  discharge,  at  ordinary 
temperatures,  it  becomes  decomposed,  after  a  time,  like  any  other 
animal  fluid;  and  this  decomposition  is  characterized  by  certain 
changes  which  take  place  in  a  regular  order  of  succession,  as  fol- 
lows : — 

After  a  few  hours  of  repose,  the  mucus  of  the  urine,  as  we  have 
mentioned  above,  collects  near  the  bottom  of  the  vessel  as  a  light, 
nearly  transparent,  cloudy  layer.  This  mucus,  being  an  organic 
substance,  is  liable  to  putrefaction;  and  if  the  temperature  to  which 
it  is  exposed  be  between  60°  and  100°  F.,  it  soon  becoines  altered, 


ACID    FERMENTATION    OF    THE    URINE.  359 

and  communicates  these  alterations  more  or  less  rapidly  to  the  super- 
natant fluid.  The  first  of  these  changes  is  called  the  acid  fermenta- 
tion of  the  urine.  It  consists  in  the  production  of  a  free  acid,  usually 
lactic  acid,  from  some  of  the  undetermined  animal  matters  con- 
tained in  the  excretion.  This  fermentation  takes  place  very  early ; 
within  the  first  twelve,  twenty-four,  or  forty-eight  hours,  according 
to  the  elevation  of  the  surrounding  temperature.  Perfectly  fresh 
urine,  as  we  have  already  stated,  contains  no  free  acid,  its  acid 
reaction  with  test  paper  being  dependent  entirely  on  the  presence 
of  biphosphate  of  soda.  Lactic  acid  nevertheless  has  been  so  fre- 
quently found  in  nearly  fresh  urine  as  to  lead  some  eminent 
chemists  (Berzelius,  Lehmann)  to  regard  it  as  a  natural  constituent 
of  the  excretion.  It  has  been  subsequently  found,  however,  that 
urine,  though  entirely  free  from  lactic  acid  when  first  passed,  may 
frequently  present  traces  of  this  substance  after  some  hours'  expo- 
sure to  the  air.  The  lactic  acid  is  undoubtedly  formed,  in  these 
cases,  by  the  decomposition  of  some  animal  substance  contained  in 
the  urine.  Its  production  in  this  way,  though  not  constant,  seems 
to  be  sufficiently  frequent  to  be  regarded  as  a  normal  process. 

In  consequence  of  the  presence  of  this  acid,  the  urates  are  par- 
tially decomposed ;  and  a  crystalline  deposit  of  free  uric  acid  slowly 
takes  place,  in  the  same  manner  as  if  a  little  nitric  or  muriatic  acid 
had  been  artificially  mixed  with  the  urine.  It  is  for  this  reason 
that  urine  which  is  abundant  in  the  urates  frequently  shows  a  de- 
posit of  crystallized  uric  acid  some  hours  after  it  has  been  passed, 
though  it  may  have  been  perfectly  free  from  deposit  at  the  time 
of  its  emission. 

During  the  period  of  the  "  acid  fermentation,"  there  is  reason  to 
believe  that  oxali.c  acid  is  also  sometimes  produced,  in  a  similar 
manner  with  the  lactic.  It  is  very  certain  that  the  deposit  of  oxa- 
late of  lime,  fe,r  from  being  a  dangerous  or  even  morbid  symptom, 
as  it  was  at  one  time  regarded,  is  frequently  present  in  perfectly 
normal  urine  after  a  day  or  two  of  exposure  to  the  atmosphere. 
We  have  often  observed  it,  under  these  circamstances,  when  no 
morbid  symptom  could  be  detected  in  connection  either  with  the 
kidneys  or  with  any  other  bodily  organ.  Now,  whenever  oxalic 
acid  is  formed  in  the  urine,  it  must  necessarily  be  deposited  under 
the  form  of  oxalate  of  lime ;  since  this  salt  is  entirely  insoluble 
both  in  water  and  in  the  urine,  even  when  heated  to  the  boiling 
point.  It  is  difficult  to  understand,  therefore,  when  oxalate  of  lime 
is  found  as  a  deposit  in  the  urine,  how  it  can  previously  have  been 


860 


EXCRETION. 


Fig.  116. 


held  in  solution.  Its  oxalic  acid  is  in  all  probability  gradually 
formed,  as  we  have  said,  in  the  urine  itself;  uniting,  as  fast  as  it  is 
produced,  with  the  lime  previously  in  solution,  and  thus  appearing 
as  a  crystalline  deposit  of  oxalate  of  lime.  It  is  much  more  probable 
that  this  is  the  true  explanation,  since,  in  the  cases  to  which  we 
allude,  the  crystals  of  oxalate  of  lime  grow,  as  it  were,  in  the  cloud 
of  mucus  which  collects  at  the  bottom  of  the  vessel,  while  the 
supernatant  fluid  remains  clear.     These  crystals  are  of  minute  size, 

transparent,  and  colorless, 
and  have  the  form  of  regular 
octohedra,  or  double  quad- 
rangular pyramids,  united 
base  to  base.  (Fig.  116.)  They 
make  their  appearance  usu- 
ally about  the  commence- 
ment of  the  second  day,  the 
urine  at  the  same  time  con- 
tinuing clear  and  retaining 
its  acid  reaction.  This  depo- 
sit is  of  frequent  occurrence 
when  no  substance  contain- 
ing oxalic  acid  or  oxalates 
has  been  taken  with  the  food. 
At  the  end  of  some  days 
the  changes  above  described 
come  to  an  end,  and  are  succeeded  by  a  diSerent  process  known  as 
the  alkaline  fermentation.  This  consists  essentially  in  the  decom- 
position or  metamorphosis  of  urea  into  carbonate  of  ammonia. 
As  the  alteration  of  the  mucus  advances,  it  loses  the  power  of  pro-' 
ducing  lactic  and  oxalic  acids,  and  becomes  a  ferment  capable  of 
acting  by  catalysis  upon  the  urea,  and  of  exciting  its  decomposition 
as  above.  We  have  already  mentioned  that  urea  may  be  converted 
into  carbonate  of  ammonia  by  prolonged  boiling  or  by  contact 
with  decomposing  animal  substances.  In  this  conversion,  the  urea 
unites  with  the  elements  of  two  equivalents  of  water ;  and  conse- 
quently it  is  not  susceptible  of  the  transformation  when  in  a  dry 
state,  but  only  when  in  solution  or  supplied  with  a  sufficient  quan- 
tity of  moisture.  The  presence  of  mucus,  in  a  state  of  incipient 
decomposition,  is  also  necessary,  to  act  the  part  of  a  catalytic 
body.  Consequently  if  the  urine,  when  first  discharged,  be  passed 
through  a  succession  of  close  filters,  so  as  to  separate  its  mucus,  it 


Oxalate  of  Lime  ;  deposited  from  healthy  urine, 
during  the  acid  fermentation. 


ALKALINE    FERMENTATIOX    OF    THE    URINE.  361 

may  be  afterward  kept,  for  an  indefinite  time,  without  alteration. 
But  under  ordinary  circumstances,  the  mucus,  as  soon  as  its  putre- 
faction has  commenced,  excites  the  decomposition  of  the  urea,  and 
carbonate  of  ammonia  begins  to  be  developed. 

The  first  portions  of  the  ammoniacal  salt  thus  produced  begin  to 
neutralize  the  biphosphate  of  soda,  so  that  the  acid  reaction  of  the 
urine  diminishes  in  intensity.  This  reaction  gradually  becomes 
weaker,  as  the  fermentation  proceeds,  until  it  at  last  disappears 
altogether,  and  the  urine  becomes  neutral.  The  production  of 
carbonate  of  ammonia  still  continuing,  the  reaction  of  the  fluid 
then  becomes  alkaline,  and  its  alkalescence  grows  more  strongly 
pronounced  with  the  constant  accumulation  of  the  ammoniacal  salt. 

The  rapidity  with  which  this  alteration  proceeds  depends  on  the 
character  of  the  urine,  the  quantity  and  quality  of  the  mucus  which 
it  contains,  and  the  elevation  of  the  surrounding  temperature.  The 
urine  passed  early  in  the  forenoon,  which  is  often  neutral  at  the 
time  of  its  discharge,  will  of  course  become  alkaline  more  readily 
than  that  which  has  at  first  a  strongly  acid  reaction.  In  the  summer, 
urine  will  become  alkaline,  if  freely  exposed,  on  the  third,  fourth, 
o.r  fifth  day ;  while  in  the  winter,  a  specimen  kept  in  a  cool  place 
may  still  be  neutral  at  the  end  of  fifteen  days.  In  cases  of  paralysis 
of  the  bladder,  on  the  other  hand,  accompanied  with  cystitis,  where 
the  mucus  is  increased  in  quantity  and  altered  in  quality,  and  the 
urine  is  retained  in  the  bladder  for  ten  or  twelve  hours  at  the  tem- 
perature of  the  body,  the  change  may  go  on  much  more  rapidly,  so 
that  the  urine  may  be  distinctly  alkaline  and  ammoniacal  at  the 
time  of  its  discharge.  In  these  cases,  however,  it  is  really  acid 
when  first  secreted  by  the  kidneys,  and  becomes  alkaline  while 
retained  in  the  interior  of  the  bladder. 

The  first  effect  of  the  alkaline  condition  of  the  urine,  thus  pro. 
duced,  is  the  precipitation  of  the  earthy  phosphates.  These  salts, 
being  insoluble  in  neutral  and  alkaline  fluids,  begin  to  precipitate  as 
soon  as  the  natural  acid  reaction  of  the  urine  has  fairly  disappeared, 
and  thus  produce  in  the  fluid  a  whitish  turbidity.  This  precipitate 
slowly  settles  upon  the  sides  and  bottom  of  the  vessel,  or  is  partly 
entangled  with  certain  animal  matters  which  rise  to  the  surface  and 
form  a  thin,  opaline  scum  upon  the  urine.  There  are  no  crystals 
to  be  seen  at  this  time,  but  the  deposit  is  entirely  amorphous  and 
granular  in  character. 

The  next  change  consists  in  the  production  of  two  new  double 
salts  by  the  action  of  carbonate  of  ammonia  on  the  phosphates  of 


362 


EXCEETION. 


soda  and  magnesia.  One  of  these  is  the  "triple  phosphate,"  phos- 
phate of  magnesia  and  ammonia  (2MgO,NHp,POj  +  2HO).  The 
other  is  the  phosphate  of  soda  and  ammonia  (NaO,]S[H40,HO;POj4- 
8H0).  The  phosphate  of  magnesia  and  ammonia  is  formed  from 
the  phosphate  of  magnesia  in  the  urine  (3MgO,POj  +  7HO)  by 
the  replacement  of  one  equivalent  of  magnesia  by  one  of  am- 
monia. The  crystals  of  this  salt  are  very  elegant  and  charac- 
teristic. They  show  themselves  throughout  all  parts  of  the  mix- 
ture ;  growing  gradually  in  the  mucus  at  the  bottom,  adhering  to 

the  sides  of  the  glass,  and 
^^'       '  scattered    abundantly    over 

the  film  which  collects  upon 
the  surface.  By  their  refract- 
ive power,  they  give  to  this 
film  a  peculiar  glistening 
and  iridescent  appearance, 
which  is  nearly  always  visi- 
ble at  the  end  of  six  or  seven 
'days.  The  crystals  are  per- 
fectly colorless  and  transpa- 
rent, and  have  the  form  of 
triangular  prisms,  generally 
with    bevelled    extremities. 

Phosphate   of    Magnesia    and    Ammonia;      (Fig.  117.)     Frequently,  also 
deposited  from  healthy  urine,  during  alkalmefermen-      ^^^-j.    ^^  ^^^    angles    are 

tation.  °  ° 

replaced  by  secondary  facets. 
They  are  insoluble  in  alkalies,  but  are  easily  dissolved  by  acids, 
even  in  a  very  dilute  form.  At  first  they  are  of  minute  size,  but 
gradually  increase,  so  that  after  seven  or  eight  days  they  may 
become  visible  to  the  naked  eye. 

The  phosphate  of  soda  and  ammonia  is  formed,  in  a  similar 
manner  to  the  above,  by  the  union  of  ammonia  with  the  phosphate 
of  soda  previously  existing  in  the  urine.  Its  crystals  resemble 
very  much  those  just  described,  except  that  their  prisms  are  of  a 
quadrangular  form,  or  some  figure  derived  from  it.  They  are 
intermingled  with  the  preceding  in  the  putrefying  urine,  and  are 
affected  in  the  same  way  by  chemical  reagents. 

As  the  putrefaction  of  the  urine  continues,  the  carbonate  of  am- 
monia which  is  produced,  after  saturating  all  the  other  ingredients 
with  which  it  is  cslpable  of  entering  into  combination,  begins  to 
be  given  off  in  a  free  form. 


The  urine  then  acquires  a  strong 


RENOVATIOX    BY    NUTRITIVE    PROCESS. 


863 


ammoniacal  odor ;  and  a  piece  of  moistened  test  paper,  held  a  little 
above  its  surface,  will  have  its  color  immediately  turned  by  the 
alkaline  gas  escaping  from  the  fluid.  This  is  the  source  of  the 
ammoniacal  vapor  which  is  so  freely  given  off  from  stables  and  from 
dung  heaps,  or  wherever  urine  is  allowed  to  remain  and  decompose. 
This  process  continues  until  all  the  urea  has  been  destroyed,  and 
until  the  products  of  its  decomposition  have  either  united  with 
other  substances,  or  have  finally  escaped  in  a  gaseous  form. 


Eenovatiojst  of  the  Body  by  the  Nutritive  Process. — We 
can  now  estimate,  from  the  foregoing  details,  the  entire  quantity  of 
material  assimilated  and  decomposed  by  the  living  body.  For  we 
have  already  seen  how  much  food  is  taken  into  the  alimentary  canal 
and  absorbed  by  the  blood  after  digestion,  and  how  much  oxygen 
is  appropriated  from  the  atmosphere  in  the  process  of  respiration. 
We  have  also  learned  the  amount  of  carbonic  acid  evolved  with  the 
breath,  and  that  of  the  various  excretory  substances  discharged  from 
the  body.  The  following  table  shows  the  absolute  quantity  of  these 
different  ingredients  of  the  ingesta  and  egesta,  compiled  from  the 
results  of  direct  experiment  which  have  already  been  given  in  the 
foregoing  pages. 


Absorbed  during  24  hours. 


Discharged  during  24  hours. 


Oxygen      . 

1.019  lbs. 

Carbonic  acid  . 

1.535  lbs 

Water 

4.735     " 

Aqueous  vapor 

1.155     " 

Albuminous  matter  . 

.396     " 

Perspiration     . 

1.930     " 

Starch 

.660     « 

W^ater  of  the  urine 

2.020     " 

Fat  . 

.220     " 

Urea  and  salts 

.110     " 

Salts 

.040     " 

Feces 

.320     " 

7.070 


7.070 


Eather  more  than  seven  pounds,  therefore,  are  absorbed  and  dis- 
charged daily  by  the  healthy  adult  human  subject ;  and,  for  a  "man 
having  the  average  weight  of  140  pounds,  a  quantity  of  material, 
equal  to  the  weight  of  the  entire  body,  thus  passes  through  the 
system  in  the  course  of  twenty  days. 

It  is  evident,  also,  that  this  is  not  a  simple  phenomenon  of  thgr 
passage,  or  filtration,  of  foreign  substances  through  the  animal 
frame.  The  materials  which  are  absorbed  actually  combine  with 
the  tissues,  and  form  a  part  of  their  substance ;  and  it  is  only  after 
undergoing  subsequent  decomposition,  that  they  finally  make  their 
appearance  in  the  excretions.  None  of  the  solid  ingredients  of  the 
food  arc  discharged   under  their  own  form  in  the  urine,  viz.,  as 


364  EXCRETION. 

starcli,  fat,  or  albumen ;  but  thej  are  replaced  by  urea  and  other 
crystallizable  substances,  of  a  difierent  nature.  Even  the  carbonic 
acid  exhaled  by  the  breath,  as  experience  has  taught  us,  is  not  pro- 
duced by  a  direct  oxidation  of  carbon ;  but  originates  by  a  steady 
process  of  decomposition,  throughout  the  tissues  of  the  body,  some- 
what similar  to  that  by  which  it  is  generated  in  the  decomposition 
of  sugar  by  fermentation.  These  phenomena,  therefore,  indicate  an 
actual  change  in  the  substance  of  which  the  body  is  composed,  and 
show  that  its  entire  ingredients  are  incessantly  renewed  under  the 
influence  of  the  vital  operations. 


SECTIOI^  II. 
NERVOUS    SYSTEM. 


CHAPTER    I. 


GENERAL    STRUCTURE    AND    FUNCTIONS    OF    THE 
NERVOUS    SYSTEM. 

In  entering  upon  the  study  of  the  nervous  system,  we  commence 
the  examination  of  an  entirely  different  order  of  phenomena  from 
those  which  have  thus  far  engaged  our  attention.  Hitherto  we 
have  studied  the  physical  and  chemical  actions  taking  place  in  the 
body  and  constituting  together  the  process  of  nutrition.  We  have 
seen  how  the  lungs  absorb  and  exhale  different  gases;  how  the 
stomach  dissolves  the  food  introduced  into  it,  and  how  the  tissues 
produce  and  destroy  different  substances  by  virtue  of  the  varied 
transformations  which  take  place  in  their  interior.  In  all  these 
instances,  we  have  found  each  organ  and  each  tissue  possessing 
certain  properties  and  performing  certain  functions,  of  a  physical 
or  chemical  nature,  which  belong  exclusively  to  it,  and  are  charac- 
teristic of  its  action. 

The  functions  of  the  nervous  system,  however,  are  neither  phy- 
sical nor  chemical  in  their  nature.  They  do  not  correspond,  in 
their  mode  of  operation,  with  any  known  phenomena  belonging  to 
these  two  orders.  The  nervous  system,  on  the  contrary,  acts  only 
upon  other  organs,  in  some  unexplained  manner,  so  as  to  excite  or 
modify  the  functions  peculiar  to  them.  It  is  not  therefore  an  appa- 
ratus which  acts  for  itself,  but  is  intended  entirely  for  the  purpose 
of  influencing,  in  an  indirect  manner,  the  action  of  other  organs. 
Its  object  is  to  connect  and  associate  the  functions  of  different 

(  365  ) 


366  GENERAL    STRUCTURE    AND    FUNCTIONS 

parts  of  the  body,  and  to  cause  them  to  act  in  harmony  with  each 
other. 

This  object  may  be  more  fully  exemplified  as  follows : — 
Each  organ  and  tissue  in  the  body  has  certain  properties  peculiar 
to  it,  which  may  be  called  into  activity  by  the  operation  of  a  stimu- 
lus or  exciting  cause.  This  capacity,  which  all  the  organs  possess, 
of  reacting  under  the  influence  of  a  stimulus,  is  called  their  excita- 
bility, or  irritability.  We  have  often  had  occasion  to  notice  this  pro- 
perty of  irritability,  in  experiments  related  in  the  foregoing  pages. 
We  have  seen,  for  example,  that  if  the  heart  of  a  frog,  after  being 
removed  from  the  body,  be  touched  with  the  point  of  a  needle,  it 
immediately  contracts,  and  repeats  the  movement  of  an  ordinary 
pulsation.  If  the  leg  of  a  frog  be  separated  from  the  thigh,  its 
integument  removed,  and  the  poles  of  a  galvanic  battery  brought 
in  contact  with  the  exposed  surface  of  the  muscles,  a  violent  con- 
traction takes  place  every  time  the  electric  circuit  is  completed. 
In  this  instance,  the  stimulus  to  the  muscles  is  supplied  by  the 
electric  discharge,  as,  in  the  case  of  the  heart  above  mentioned,  it  is 
supplied  by  the  contact  of  the  steel  needle ;  and  in  both,  a  muscu- 
lar contraction  is  the  immediate  consequence.  If  we  introduce  a 
metallic  catheter  into  the  empty  stomach  of  a  dog  through  a  gastric 
fistula,  and  gently  irritate  with  it  the  mucous  membrane,  a  secretion 
of  gastric  juice  at  once  begins  to  take  place ;  and  if  food  be  intro- 
duced the  fluid  is  poured  out  in  still  greater  abundance.  We  know 
also  that  if  the  integument  be  exposed  to  contact  with  a  heated 
body,  or  to  friction  with  an  irritating  liquid,  an  excitement  of  the 
circulation  is  at  once  produced,  which  again  passes  away  after  the 
removal  of  the  irritating  cause. 

In  all  these  instances  we  find  that  the  organ  which  is  called  into 
^.ctivity  is  excited  by  the  direct  application  of  some  stimulus  to  its 
own  tissues.  But  this  is  not  usually  the  manner  in  which  the  dif- 
ferent functions  are  excited  during  life.  The  stimulus  which  calls 
into  action  the  organs  of  the  living  body  is  usually  not  direct,  but 
indirect  in  its  operation.  Yery  often,  two  organs  which  are  situ- 
ated in  distant  parts  of  the  body  are  connected  with  each  other  by 
such  a  sympathy,  that  the  activity  of  one  is  influenced  by  the 
condition  of  the  other.  The  muscles,  for  example,  are  almost  never 
called  into  action  by  an  external  stimulus  operating  directly  upon 
their  own  fibres,  but  by  one  which  is  applied  to  some  other  organ, 
either  adjacent  or  remote.  Thus  the  peristaltic  action  of  the  mus- 
cular coat  of  the  intestine  commences  when  the  food  is  brought  in 


OF    THE    NERVOUS    SYSTEM.  367 

contact  with  its  nnlcous  membrane.  The  lachrymal  gland  is  excited 
to  increased  activity  by  anything  which  causes  irritation  of  the 
conjunctiva.  In  all  such  instances,  the  physiological  connection 
between  two  diflferent  organs  is  established  through  the  medium  of 
the  nervous  system. 

The  function  of  the  nervous  system  may  therefore  be  defined,  in 
the  simplest  terms,  as  follows :  It  is  intended  to  associate  the  different 
parts  of  the  body  in  such  a  manner,  that  stimulus  applied  to  one  organ 
m,ay  excite  the  activity  of  another. 

The  instances  of  this  mode  of  action  are  exceedingly  numerous. 
Thus,  the  light  which  falls  upon  the  retina  produces  a  contraction 
of  the  pupil.  The  presence  of  food  in  the  stomach  causes  the  gall- 
bladder to  discharge  its  contents  into  the  duodenum.  The  expul- 
sive efforts  of  coughing  are  excited  by  a  foreign  body  entangled  in 
the  glottis. 

It  is  easy  to  understand  the  great  importance  of  this  function, 
particularly  in  the  higher  animals  and  in  man,  whose  organization 
is  an  exceedingly  complicated  one.  For  the  different  organs  of 
the  body,  in  order  to  preserve  the  integrity  of  the  whole  frame, 
must  not  only  act  and  perform  their  functions,  but  they  must  act  in 
harmony  with  each  other,  and  at  the  right  time,  and  in  the  right 
direction.  The  functions  of  circulation,  of  respiration,  and  of 
digestion,  are  so  mutually  dependent,  that  if  their  actions  do  not 
take  place  harmoniously,  and  in  proper  order,  a  serious  disturb- 
ance must  inevitably  follow.  When  the  muscular  system  is  ex- 
cited by  unusual  exertion,  the  circulation  is  also  quickened.  The 
blood  arrives  more  rapidly  at  the  heart,  and  is  sent  in  greater 
quantity  to  the  lungs.  If  the  movements  of  respiration  were  not 
accelerated  at  the  same  time,  through  the  connections  of  the  nerv- 
ous system,  there  would  immediately  follow  deficiency  of  aeration, 
vascular  congestion,  and  derangement  of  the  circulation.  If  the 
iris  were  not  stimulated  to  contract  by  the  influence  of  the  light 
falling  on  the  retina,  the  delicate  expansion  of  the  optic  nerve 
would  be  dazzled  by  any  unusual  brilliancy,  and  vision  would  be 
obscured  or  confused.  In  all  the  higher  animals,  therefore,  where 
the  different  functions  of  the  body  are  performed  by  distinct  organs, 
situated  in  different  parts  of  the  frame,  it  is  necessary  that  their 
action  should  be  thus  regulated  and  harmonized  by  the  operation 
of  the  nervous  system. 


368  GENEEAL    STRUCTURE    AND    FUNCTIONS 

The  manner  in  which  this  is  accomplished  is  as  follows : — 

The  nervous  system,  however  simjAe  or  however  complicated  it 
may  be,  consists  always  of  two  different  kinds  of  tissue,  which  are 
distinguished  from  each  other  by  their  color,  their  structure,  and 
their  mode  of  action.  One  of  these  is  known  as  the  white  substance, 
or  the  fibrous  tissue.  It  constitutes  the  whole  of  the  substance  of 
the  nervous  trunks  and  branches,  and  is  found  in  large  quantity  on 
the  exterior  of  the  spinal  cord,  and  in  the  central  parts  of  the  brain 
and  cerebellum.  In  the  latter  situations,  it  is  of  a  soft  consistency, 
like  curdled  cream,  and  of  a  uniform,  opaque  white  color.  In 
the  trunks  and  branches  of  the  nerves  it  has  the  same  opaque 
white  color,  but  is  at  the  same  time  of  a  firmer  consistency,  owing 
to  its  being  mingled  with  condensed  areolar  tissue.  Examined  by 
the  microscope,  the  white  substance  is  seen  to  be  composed  every- 
where of  minute  fibres  or  filaments,  the  "ultimate  nervous  fila- 
ments," running  in  a  direction  very  nearly  parallel  with  each  other. 
These  filaments  are  cylindrical  in  shape,  and  vary  considerably  in 
size.  Those  which  are  met  with  in  the  spinal  cord  and  the  brain 
are  the  smallest,  and  have  an  average  diameter  of  to^tto  of  an 
inch.  In  the  trunks  and  branches  of  the  nerves  they  average  aii'o  rr 
of  an  inch. 

The  structure  of  the  ultimate  nervous  filament  is  as  follows: 
The  exterior  of  each  filament  consists  of  a  colorless,  transparent 
tubular  membrane,  which  is  seen  with  some  difficulty  in  the  natural 
condition  of  the  fibre,  owing  to  the  extreme  delicacy  of  its  texture, 
and  to  its  cavity  being  completely  filled  with  a  substance  very 
similar  to  it  in  refractive  power.  In  the  interior  of  this  tubular 
membrane  there  is  contained  a  thick,  semi-fluid  nervous  matter, 
which  is  Avhite  and  glistening  by  reflected  light,  and  is  called  the 
"white  substance  of  Schwann,"  Finally,  running  longitudinally 
through  the  central  part  of  each  filament,  is  a  narrow  ribbon- 
shaped  cord,  of  rather  firm  consistency,  and  of  a  semi-transparent 
grayish  color.  This  central  portion  is  called  the  "  axis  cylinder," 
or  the  "  flattened  band."  It  is  enveloped  everywhere  by  the  semi- 
fluid white  substance,  and  the  whole  invested  by  the  external  tubu- 
lar membrane. 

When  nervous  matter  is  prepared  for  the  microscope  and  exa- 
mined by  transmitted  light,  two  remarkable  appearances  are  ob- 
served in  its  filaments,  produced  by  the  contact  of  foreign  sub- 
stances. In  the  first  place  the  unequal  pressure,  to  which  the  fila- 
ments are  accidentally  subjected  in  the  process  of  dissection  and 


OF    THE    NERVOUS    SYSTEM. 


369 


Fk'.  118. 


preparation,  produces  an  irregularly  bulging  or  varicose  appearance 
in  them  at  various  points,  owing  to  the  readiness  with  which  the 
semi-fluid  white  substance  in  their  interior  is  displaced  in  different 
directions.  (Fig.  118.)  Sometimes  spots  may  be  seen  here  and 
there,  where  the  nervous  matter  has  been  entirely  pressed  apart  in 
the  centre  of  a  filament,  so 
that  there  appears  to  be  an 
entire  break  in  its  continuity, 
while  the  investing  mem- 
brane may  be  still  seen,  pass- 
ing across  from  one  portion 
to  the  other.  When  a  nerv- 
ous filament  is  torn  across 
under  the  microscope  and 
subjected  to  pressure,  a  cer- 
tain quantity  of  the  semi- 
fluid white  substance  is 
pressed  out  from  its  torn 
extremity,  and  may  be  en- 
tirely separated  from  it,  so 
as  to  present  itself  under  the      nervous  filaments  from  white  substanje  oi 

f,  .  ,       ,  ,     ,      brain. — a,  a,  a.  Soft  substance   of  the  filaments  pressed 

tOrm  Ot  irregularly  rounded     out,  and  floating  m  irregularly  rounded  drops. 

drops  of  various  sizes  (a,  a, 

a),  scattered  over  the  field  of  the  microscope.  The  varicose  appear- 
ance above  alluded  to  is  more  frequently  seen  in  the  smaller  nerv- 
ous filaments  from  the  brain  and  spinal  cord,  owing  to  their  soft 
consistency  and  the  readiness  with  which  they  yield  to  pressure. 

The  second  effect  produced  by  the  artificial  preparation  of  the 
nervous  matter  is  a  partial  coagulation  of  the  white  substance  of 
Schwann.  In  its  natural  condition  this  substance  has  the  same 
consistency  throughout,  and  appears  perfectly  transparent  and 
homogeneous  by  transmitted  light.  As  soon,  however,  as  the  nerv- 
ous filament  is  removed  from  its  natural  situation,  and  brought  in 
contact  with  air,  water,  or  other  unnatural  fluids,  the  soft  substance 
immediately  under  the  investing  membrane  begins  to  coagulate. 
It  increases  in  consistency,  and  at  the  same  time  becomes  more 
highly  refractive;  so  that  it  presents  on  each  side,  immediately 
underneath  the  investing  membrane,  a  thin  layer  of  a  peculiar 
glistening  aspect.  (Fig.  119.)  At  first,  this  change  takes  place 
only  in  the  outer  portions  of  the  white  substance  of  Schwann. 
The  coagulating  process,  however,  subsequently  goes  on,  and 
24 


370 


GENERAL    STRUCTURE    AND    FUNCTIONS 


Fig.  119. 


gradually  advances  from  the  edges  of  the  filament  toward  its 
centre,  until  its  entire  thickness  after  a  time  presents  the  same 
appearance.  The  effect  of  this  process  can  also  be  seen  in  those 
portions  of  the  white  substance  which  have  been  pressed  out  from 
the  interior  of  the  filaments,  and  which  float  about  in  the  form  of 

drops.  (Fig.  118,  a.)  These 
drops  are  always  covered 
with  a  layer  of  coagulated 
material  which  is  thicker 
and  more  opaque  in  propor- 
tion to  the  length  of  time 
which  has  elapsed  since  the 
commencement  of  the  alter- 
ation. 

The  nervous  filaments 
have  essentially  the  same 
structure  in  the  brain  and 
spinal  cord  as  in  the  nervous 
trunks  and  branches ;  only 
they  are  of  much  smaller 
size  in  the  former  than  in 
the  latter  situation.  In  the 
nervous  trunks  and  branches, 
however,  outside  the  cranial 
and  spinal  cavities,  there 
exists,  superadded  to  the 
nervous  filaments  and  interwoven  with  them,  a  large  amount  of 
condensed  areolar  or  fibrous  tissue,  which  protects  them  from 
injury,  and  gives  to  this  portion  of  the  nervous  system  a  peculiar 
density  and  resistance.  This  difference  in  consistency  between  the 
white  substance  of  the  nerves  and  that  of  the  brain  and  spinal  cord 
is  owing,  therefore,  exclusively  to  the  presence  of  ordinary  fibrous 
tissue  in  the  nerves,  while  it  is  wanting  in  the  brain  and  spinal 
cord.  The  consistency  of  the  nervous  filaments  themselves  is  the 
same  in  each  situation. 

The  nervous  filaments  are  arranged,  in  the  nervous  trunks  and 
branches,  in  a  direction  nearly  parallel  with  each  other.  A  certain 
number  of  them  are  collected  in  the  form  of  a  bundle,  which  is 
invested  with  a  layer  of  fibrous  tissue,  in  which  run  the  small 
bloodvessels,  destined  for  the  nutrition  of  the  nerve.  These  pri- 
mary bundles  are  again  united  into  secondary,  the  secondary  into 


Nervous  Filaments  from  sciatic  nerve,  shoTring 
their  coagulation.  —  At  ri,  the  torn  extremity  of  a 
nervous  filament  with  the  axis  cylinder  (b)  protruding 
from  it.  At  e,  the  white  suhstance  of  Schwann  is  nearly 
separated  by  accidental  compression,  but  the  axis- 
cylinder  passes  across  the  ruptured  portion.  The  out- 
line of  the  tubular  membrane  is  also  seen  at  c  on  the 
outside  of  the  nervous  filament. 


OF    THE    NERVOUS    SYSTEM. 


371 


tertiary,  &c.  A  nerve,  therefore,  consists  of  a  large  bundle  of  ulti- 
mate filaments,  associated  with  each  other  in  larger  or  smaller 
packets,  and  bound  together  by  the  investing  fibrous  layers.  When 
a  nerve  is  said  to  become  branched  or  "  divided"  in  any  part  of  its 
course,  this  division  merely  implies  that  some  of  its  filaments  leave 
the  bundles  with  which  they  were 
previously  associated,  and  pursue  Fig-  120. 

a  different  direction.  (Fig.  120.) 
A  nerve  which  originates,  for  ex- 
ample, from  the  spinal  cord  in  the 
region  of  the  neck,  and  runs  down 
the  upper  extremity,  dividing  and 
subdividing,  to  be  finally  distri- 
buted to  the  integument  and  mus- 
cles of  the  hand,  contains  at  its 
point  of  origin  all  the  filaments 
into  which  it  is  afterward  divided, 
and  which  are  merely  separated 
at  successive  points  from  the 
main  bundle.  The  ultimate  fila- 
ments, accordingly,  are  continu- 
ous throughout,  and  do  not  them- 
selves divide  at  any  point  between 
their  origin  and  their  final  distri- 
bution. 

When  a  nerve,  furthermore,  is 
said  to  "  inosculate"  with  another 
nerve,  as  when  the  infra-orbital 
inosculates  with  the  facial,  or  the 
cervical   nerves   inosculate  with 

each  other,  this  means  simply  that  some  of  the  filaments  composing 
the  first  nervous  bundle  separate  from  it,  and  cross  over  to  form  a 
part  of  the  second,  while  some  of  those  belonging  to  the  second 
cross  over  and  join  the  first  (Fig.  121) ;  but  the  individual  filaments 
in  each  instance  remain  continuous  and  preserve  their  identity 
throughout.  This  fact  is  of  great  physiological  importance;  since 
the  white  or  fibrous  nerve-substance  is  everywhere  simply  an 
organ  of  transmission.  It  serves  to  convey  the  nervous  impulse  in 
various  directions,  from  without  inward,  or  from  within  outward ; 
and  as  each  nervous  filament  acts  independently  of  the  others,  it 
will  convey  an  impression   or  a  stimulus  continuously  from  its 


Division  of  a  Nekvk,  showing  portion  of 
nervous  trunk  ("),  aud  the  separation  of  its 
filatneutii  (b,  c,  d,  t). 


070 


GENERAL    STRUCTURE    AND    FUNCTIONS 


origin  to  its  termination,  and  will  always  have  tbe  same  character 
and  function  in  every  part  of  its  course. 

The  other  variety  of  nervous  matter  is  known  as  the  gray  sub- 
stance.    It  is  sometimes  called  "cineritious  matter,"  and  sometimes 


Fig.  121. 


Inosculation  of  N  u  k  v  e  s . 


"  vesicular  neurine  "     It  is  found  in  the  central  parts  of  the  spinal 
cord,  at  the  base  of  the  brain  in  isolated  masses,  and  is  also  spread 

out  as  a  continuous  layer  on 
^^'  the  external  portions  of  the 

cerebrum  and  cerebellum. 
It  also  constitutes  the  sub- 
stance of  all  the  ganglia  of 
the  great  sympathetic.  Ex- 
amined by  the  microscope,  it 
consists  of  vesicles  or  cells,  of 
various  forms  and  sizes,  im- 
bedded in  a  grayish,-  granular, 
intercellular  substance,  and 
containing,  also,  very  fre- 
quently, granules  of  grajdsh 
pigmentary  matter.  It  is  to 
the  presence  of  this  granular 

Nbrv«   Cblls,   intermiagled    with  fibres;  fron>  ■  ^     ^^^     ^^^^    ^^^^    ^f 

semilunar  ganglion  of  cat.  ^ji^myj^u 


OF    THE    NERVOUS    SYSTEM.  373 

nervous  matter  owes  the  ashy  or  "  cineritious"  color  from  which  it 
derives  its  name.  The  cells  composing  it  vary  in  size,  according 
to  Kolliker,  from  4t)V(7  l^o  g-^jj  of  an  inch.  The  largest  of  them  have 
a  very  distinct  nucleus  and  nucleolus.  (Fig.  122.)  Many  of  them 
are  provided  with  long  processes  or  projections,  which  are  sometimes 
divided  into  two  or  three  smaller  branches.  These  cells  are  inter- 
mingled, in  all  the  collections  of  gray  matter,  with  nervous  filaments, 
and  are  entangled  with  their  extremities  in  such  a  manner  that  it 
is  exceedingly  difficult  to  ascertain  the  exact  nature  of  the  anato- 
mical relations  existing  between  them.  It  is  certain  that  in  some 
instances  the  slender  processes  running  out  from  the  nervous  vesi- 
cles become  at  last  continuous  with  the  filaments;  but  it  is  not 
known  whether  this  be  the  case  in  all  or  even  in  a  majority  of 
instances.  The  extremities  of  the  filaments,  however,  are  at  all 
events  brought  into  very  close  relation  with  the  vesicles  or  cells  of 
the  gray  matter. 

Every  collection  of  gray  matter,  whatever  be  its  situation  or 
relative  size  in  the  nervous  system,  is  called  a  ganglion  or  nervous 
centre.  Its  function  is  to  receive  impressions  conveyed  to  it  by  the 
nervous  filaments,  and  to  send  out  by  them  impulses  which  are  to 
be  transmitted  to  distant  organs.  The  ganglia,  therefore,  originate 
nervous  power,  so  to  speak ;  while  the  filaments  and  the  nerves 
only  transmit  it.  Now  we  shall  find  that,  in  the  structure  of  every 
nervous  system,  the  ganglia  are  connected,  first  with  the  differenc 
organs,  by  bundles  of  filaments  which 
are  called  nerves ;  and  secondly  with  Fig'  123. 

each  other,  by  other  bundles  which 
are  termed  commissures.  The  entire 
system  is  accordingly  made  up  of 
ganglia,  nerves,  and  commissures. 

The  simplest  form  of  nervous 
system  is  probably  that  found  in 
the  five-rayed  starfish.  This  animal 
belongs  to  the  type  known  as  radiata; 
that  is,  animals  whose  organs  radiate 
from  a  central  point,  so  as  to  form  a 
circular  series  of  similar  parts,  each 
organ  being  repeated  at  different  nervocs  system  of  starfish., 
points   of  the   circumference.     Tke 

starfish  (Fig.  123)  consists  of  a  central  mass,  with  five  arms  or 
limbs  radiating  from  it.     In  tlie  centre  is  the  mouth,  and  immedi- 


374  GENERAL    STRUCTURE    AND    FUNCTIONS 

ately  beneath  it  the  stomach  or  digestive  cavity,  which  sends  pro- 
longations into  every  one  of  the  projecting  limbs.  There  is  also 
contained  in  each  limb  a  portion  of  the  glandular  and  muscular 
systems,  and  the  whole  is  covered  by  a  sensitive  integument.  The 
nervous  system  consists  of  five  similar  ganglia,  situated  in  the 
central  portion,  at  the  base  of  the  arms.  These  ganglia  are  con- 
nected with  each  other  by  commissures,  so  as  to  form  a  nervous 
collar  or  chain,  surrounding  the  orifice  of  the  digestive  cavity. 
Each  ganglion  also  sends  off  nerves,  the  filaments  of  which  are 
distributed  to  the  organs  contained  in  the  corresponding  limb. 

We  have  already  stated  that  the  proper  function  of  the  nervous 
system  is  to  enable  a  stimulus,  acting  upon  one  organ,  to  produce 
motion  or  excitement  in  another.  This  is  accomplished,  in  the 
starfish,  in  the  following  manner : — 

When  any  stimulus  or  irritation  is  applied  to  the  integument  of 
one  of  the  arms,  it  is  transmitted  by  the  nerves  of  the  integument 
to  the  ganglion  situated  near  the  mouth.  Arrived  here,  it  is 
received  by  the  gray  matter  of  the  ganglion,  and  immediately  con- 
verted into  an  impulse  which  is  sent  out  by  other  filaments  to  the 
muscles  of  the  corresponding  limb;  and  a  muscular  contraction  and 
movement  consequently  take  place.  The  muscles  therefore  contract 
in  consequence  of  an  irritation  which  has  been  applied  to  the  skin. 
This  is  called  the  "  reflex  action"  of  the  nervous  system ;  because  the 
stimulus  is  first  sent  inward  by  the  nerves  of  the  integument,  and 
then  returned  or  reflected  back  from  the  ganglion  upon  the  muscles. 
It  must  be  recollected  that  this  action  does  not  necessarily  indicate 
any  sensation  or  volition,  nor  even  any  consciousness  on  the  part  of 
the  animal.  The  function  of  the  gray  matter  is  simply  to  receive 
the  impulse  conveyed  to  it,  and  to  reflect  or  send  back  another ; 
and  this  may  be  accomplished  altogether  involuntarily,  and  without 
the  existence  of  any  conscious  perception. 

Where  the  irritation  applied  to  the  integument  is  of  an  ordinary 
character  and  not  very  intense,  it  is  simply  reflected,  as  above 
described,  from  the  corresponding  ganglion  back  to  the  same  limb. 
But  if  it  be  of  a  peculiar  character,  or  of  greater  intensity  than  usual, 
it  may  be  also  transmitted  by  the  commissures  to  the  neighboring 
ganglia ;  and  so  two,  three,  four,  or  even  all  five  of  the  limbs  may 
be  set  in  motion  by  a  stimulus  applied  to  the  integument  of  one  of 
them.  Now,  as  all  the  limbs  of  the  animal  have  the  same  structure 
and  contain  the  same  organs,  their  action  will  also  be  the  same ; 
and  the  effects  of  this  communication  of  the  stimulus  from  one  to 


OF    THE    NERVOUS    SY8TEM. 


375 


the  other  by  means  of  commissures  will  be  a  repetition,  or  rather 
a  simultaneous  production  of  similar  movements  in  different  parts 
of  the  body.  According  to  the  character  and  intensity,  therefore, 
of  the  original  stimulus,  it  will  be  followed  by  a  response  from 
one,  several,  or  all  of  the  different  parts  of  the  animal  frame. 

It  will  be  seen  also  that  there  are  two  kinds  of  nervous  filaments, 
differing  essentially  in  their  functions.  One  set  of  these  fibres  run 
from  the  sensitive  surfaces  to  the  ganglion,  and  convey  the  nervous 
impression  inward.  These  are  called  sensitive  fibres.  The  other 
set  run  from  the  ganglion  to  the  muscles,  and  carry  the  nervous 
impression  outward.     These  are  called  motor  fibres. 

In  the  starfish,  where  the  body  is  composed  of  a  repetition  of  simi- 
lar parts  arranged  round  a  common  centre,  and  where  all  the  limbs 
are  precisely  alike  in  structure,  the  several  ganglia  composing  the 
nervous  system  are  also  similar  to  each  other,  and  act  in  the  same 
way.  But  in  animals  which  are  constructed  upon  a  different  plan, 
and  whose  bodies  are  composed  of  distinct  organs,  situated  in  dif- 
ferent regions,  we  find  that  the  nervous  ganglia,  presiding  over 
the  function  of  these  organs,  present  a  corresponding  degree  of 
dissimilarity. 

In  Aplysia,  for  example,  which  belongs  to  the  type  of  mollusca. 
or  soft-bodied  animals,  the  digestive  apparatus  consists  of  a  mouth, 
an  oesophagus,  a  triple  stomach,  and  a  some- 
what convoluted  intestine.  The  liver  is 
large,  and  placed  on  one  side  of  the  body, 
while  the  gills,  in  the  form  of  vascular 
laminge,  occupy  the  opposite  side.  There 
are  both  testicles  and  ovaries  in  the  same 
animal,  the  male  and  female  functions  co- 
existing, as  in  many  other  invertebrate 
species.  All  the  organs,  furthermore,  are 
here  arranged  without  any  reference  to  a 
regular  or  symmetrical  plan.  The  body  is 
covered  with  a  muscular  mantle,  which  ex- 
pands at  the  ventral  surface  into  a  tolerably 
well-developed  "  foot,"  or  organ  of  locomo- 
tion, by  which  the  animal  is  enabled  to 
change   its  position  and   move   from  one      nebvous      ststrm     op 

,         ,.,       ,  ^i  Apr.TsiA.  — 1.       Digestive    or 

lOCahty  to  another.  ocsoplmKeal  ganglion.     2.     Cere- 

The  nervous  system  of  this  animal  is  con-    '"•'^'  g^iff'ion.    3,  3.  redai  or 

-  .  locomotory  ganglia.      4.    Respi- 

structed  upon  a  plan  correspondmg  with    ratory  gangiiou. 


Fig.  124. 


376 


GENEEAL    STRUCTURE    AND    FUNCTIONS 


that  of  the  entire  body.  (Fig.  124.)  There  is  a  small  ganglion  (i) 
situated  anteriorly,  which  sends  nerves  to  the  commencement  of  the 
digestive  apparatus,  and  is  regarded  as  the  oesophageal  or  digestive 
ganglion.  Immediately  behind  it  is  a  larger  one  (2)  called  the 
cephalic  or  cerebral  ganglion,  which  sends  nerves  to  the  organs  of 
special  sense,  and  which  is  regarded  as  the  seat  of  volition  and 
general  sensation  for  the  entire  body.  Following  this  is  a  pair  of 
ganglia  (3,  3),  the  pedal  or  locomotory  ganglia,  which  supply  the 
muscular  mantle  and  its  foot-like  expansion,  and  which  regulate 
the  movement  of  these  organs.  Finally,  another  ganglion  (4),  situ- 
ated at  the  posterior  part  of  the  body,  sends  nerves  to  the  branchiae 
or  gills,  and  is  termed  the  branchial  or  respiratory  ganglion.  All 
these  nervous  centres  are  connected  by  commissures  with  the  central 
or  cerebral  ganglion,  and  may  therefore  act  either  independently 
or  in  association  with  each  other,  by  means  of  these  connecting  fibres. 
In  the  third  type  of  animals,  again,  viz.,  the  articulata,  the  gene- 
ral plan  of  structure  of  the  body  is  different  from 
Fig.  125.  the  foregoing,  and  the  nervous  system  is  accord- 

ingly modified  to  correspond  with  it.  In  these 
animals,  the  body  is  composed  of  a  number  of 
rings  or  sections,  which  are  articulated  with  each 
other  in  linear  series.  A  very  good  example  of 
this  type  may  be  found  in  the  common  centipede, 
or  scolopendra.  Here  the  body  is  composed  of 
twenty -two  successive  and  nearly  similar  articu- 
lations, each  of  which  has  a  pair  of  legs  attached, 
and  contains  a  portion  of  the  glandular,  respira- 
tory, digestive  and  reproductive  apparatuses. 
The  animal,  therefore,  consists  of  a  repetition  of 
similar  compound  parts,  arranged  in  a  longitudi- 
nal chain  or  series.  The  only  exceptions  to  this 
similarity  are  in  the  first  and  last  articulations. 
The  first  is  large,  and  contains  the  mouth ;  the 
last  is  small,  and  contains  the  anus.  The  first 
articulation,  which  is  called  the-  "head,"  is  also 
furnished  with  eyes,  with  antennae,  and  with  a 
pair  of  jaws,  or  mandibles. 

The  nervous  system  of  the  centipede  (Fig.  125), 
corresponding  in  structure  with  the  above  plan, 
consists  of  a  linear  series  of  nearly  equal  and  similar  ganglia  arranged 
in  pairs,  situated  upon  the  median  line,  along  the  ventral  surface  of 


NERVOtre   System 
OF  Ckstipede. 


OF   THE    NERVOUS    SYSTEM.  377 

tlie  alimentary  canal.  Each  pair  of  ganglia  is  connected  witli  the 
integument  and  muscles  of  its  own  articulation  by  sensitive  and 
motor  filaments ;  and  with  those  which  precede  and  follow  by  a 
double  cord  of  longitudinal  commissural  fibres.  In  the  first  articu- 
lation, moreover,  or  the  head,  the  ganglia  are  larger  than  elsewhere, 
and  send  nerves  to  the  antennse  and  to  the  organs  of  special  sense. 
This  pair  is  termed  the  cerebral  ganglion,  or  the  "  brain." 

A  reflex  action  may  take  place,  in  these  animals,  through  either 
one  or  all  of  the  ganglia  composing  the  nervous  chain.  An  im- 
pression received  by  the  integument  of  any  part  of  the  body  may 
be  transmitted  inward  to  its  own  ganglion  and  thence  reflected 
immediately  outward,  so  as  to  produce  a  movement  of  the  limbs 
belonging  to  that  articulation  alone;  or  it  may  be  propagated, 
through  the  longitudinal  commissures,  forward  or  backward,  and 
produce  simultaneous  movements  in  several  neighboring  articula- 
tions ;  or,  finally,  it  may  be  propagated  quite  up  to  the  anterior  pair 
of  ganglia  or  "  brain,"  where  its  reception  will  be  accompanied  with 
consciousness,  and  a  voluntary  movement  reflected  back  upon  any 
or  all  of  the  limbs  at  once.  The  organs  of  special  sense,  also,  com- 
municate directly  with  the  cerebral  ganglia ;  and  impressions  con- 
veyed through  them  may  accordingly  give  rise  to  movements  in 
any  distant  part  of  the  body.  In  these  animals  the  ventral  ganglia, 
or  those  which  simply  stand  as  a  medium  of  communication  be- 
tween the  integument  and  the  muscles,  are  nearly  similar  through- 
out ;  while  the  first  pair,  or  those  which  receive  the  nerves  of  special 
sense,  and  which  exercise  a  general  controlling  power  over  the  rest 
of  the  nervous  system,  are  distinguished  from  the  remainder  by  a 
well-marked  preponderance  in  size. 

In  the  centipede  it  will  be  noticed  that  nearly  all  the  organs  and 
functions  are  distributed  in  an  equal  degree  throughout  the  whole 
length  of  the  body.  The  organs  of  special  sense  alone,  with  those 
of  mastication  and  the  functions  of  perception  and  volition,  are 
confined  to  the  head.  The  ganglia  occupying  this  part  are  there- 
fore the  only  ones  which  are  distinguished  by  any  external  pecu- 
liarities ;  the  remainder  being  nearly  uniform  both  in  size  and 
activity.  In  some  kinds  of  articulated  animals,  however,  particular 
functions  are  concentrated,  to  a  greater  or  less  extent,  in  particular 
parts  of  the  body;  and  the  nervous  ganglia  which  preside  over 
them  are  modified  in  a  corresponding  manner.  In  the  insects, 
for  example,  the  body  is  divided  into  three  distinct  sections,  viz : 
the   head,  containing  the  organs  of  prehension,  mastication,  tact 


878  GENERAL    STRUCTURE    AND    FUNCTIONS 

and  special  sense ;  fhe  chest,  upon  which  are  concentrated  the  or- 
gans of  locomotion,  the  legs  and  wings ;  and  the  abdomen,  contain- 
ing the  greater  part  of  the  alimentary  canal,  together  with  the 
glandular  and  generative  organs.  As  the  insects  have  a  greater 
amount  of  intelligence  and  activity  than  the  centipedes  and  other 
worm-like  articulata,  and  as  the  organs  of  special  sense  are  more 
perfect  in  them,  the  cerebral  ganglia  are  also  unusually  developed, 
and  are  evidently  composed  of  several  pairs,  connected  by  commis- 
sures so  as  to  form  a  compound  mass.  As  the  organs  of  locomo- 
tion, furthermore,  instead  of  being  distributed,  as  in  the  centipede, 
throughout  the  entire  length  of  the  animal,  are  concentrated  upon 
the  chest,  the  locomotory  ganglia  also  preponderate  in  size  in  this 
region  of  the  body ;  while  the  ganglia  which  preside  over  the  secre- 
tory and  generative  functions  are  situated  together,  in  the  cavity  of 
the  abdomen. 

All  the  above  parts,  however,  are  connected,  in  the  same  manner 
as  previously  described,  with  the  anterior  or  cerebral  pair  of  gan- 
glia. In  all  articulate  animals,  moreover,  the  general  arrangement 
of  the  body  is  symmetrical.  The  right  side  is,  for  the  most  part, 
precisely  like  the  left,  as  well  in  the  internal  organs  as  in  the  ex- 
ternal covering  and  the  locomotory  appendages.  The  only  marked 
variation  between  different  parts  of  the  body  is  in  an  antero-pos- 
terior  direction ;  owing  to  different  organs  being  concentrated,  in 
some  cases,  in  the  head,  chest,  and  abdomen. 

Finally,  in  the  vertebrate  type  of  animals,  comprising  man,  the 
quadrupeds,  birds,  reptiles,  and  fish,  the  external  parts  of  the  body, 
together  with  the  locomotory  apparatus  and  the  organs  of  special 
sense,  are  symmetrical,  as  in  the  articulata ;  but  the  internal  organs, 
especially  those  concerned  in  the  digestive  and  secretory  functions, 
are  unsymmetrical  and  irregular,  as  in  the  molluscs.  The  organs 
of  respiration,  however,  are  nearly  symmetrical  in  the  vertebrata, 
for  the  reason  that  the  respiratory  movements,  upon  which  the 
function  of  these  organs  is  immediately  dependent,  are  performed 
by  muscles  belonging  to  the  general  locomotory  apparatus.  The 
nervous  system  of  the  vertebrata  partakes,  accordingly,  of  the  struc- 
tural arrangement  of  the  organs  under  its  control.  That  portion 
which  presides  over  the  locomotory,  respiratory,  sensitive,  and  in- 
tellectual functions  forms  a  system  by  itself,  called  the  cerebrospinal 
system.  This  system  is  arranged  in  a  manner  very  similar  to  that 
of  the  articulata.  It  is  composed  of  two  equal  and  symmetrical 
halves,  running  along  the  median  line  of  the  body,  the  different 


OF    THE    NERVOUS    SYSTEM. 


379 


parts  of  whicli  are  connected  by  transverse  and  longitudinal  com- 
missures. Its  ganglia  occupy  the  cavities  of  the  cranium  and  the 
spinal  canal,  and  send  out  their  nerves  through  openings  in  the 
bony  walls  of  these  cavities. 

The  other  portion  of  the  nervous  system  of  vertebrata  is  that 
which  presides  over  the  functions  of  vegetative  life.  It  is  called 
the  ganglionic  or  great  sympathetic  system.  Its  ganglia  are  situated 
anteriorly  to  the  spinal  column,  in  the  visceral  cavities  of  the  body, 
and  are  connected,  like  the  others,  by  transverse  and  longitudinal 
commissures.  This  part  of  the  nervous  system  is  symmetrical  in 
the  neck  and  thorax,  but  is  uusymmetrical  in  the  abdomen,  where 
it  attains  its  largest  size  and  its  most  complete  development. 

The  vertebrate  animals,  as  a  general  rule,  are  very  much  superior 
to  the  other  classes,  in  intelligence  and  activity,  as  well  as  in  the 
variety  and  complicated  character  of  their  motions;  while  their 
nutritive    or   vegetative  functions, 
on  the  other  hand,  are  not  particu-  Fig-  126. 

larly  well  developed.  Accordingly 
we  find  that  in  these  animals  the 
cerebro-spinal  system  of  nerves 
preponderates  very  much,  in  im- 
portance and  extent,  over  that  of 
the  great  sympathetic.  The  quan- 
tity of  nervous  matter  contained 
in  the  brain  and  spinal  cord  is, 
even  in  the  lowest  vertebrate  ani- 
mal, very  much  greater  than  that 
contained  in  the  system  of  the  great 
sympathetic;  and  this  preponder- 
ance increases,  in  the  higher  classes, 
just  in  proportion  to  their  supe- 
riority in  intelligence,  sensation, 
power  of  motion,  and  other  func- 
tions of  a  purely  animal  character. 

The  spinal  cord  is  yQTj  nearly 
alike  in  the  different  classes  of  ver- 
tebrate animals.  It  is  a  nearly 
cylindrical  cord,  running  from  one 
end  of  the  spinal  canal  to  the  other, 
and  connected  at  its  anterior  ex- 
tremity with  the  ganglia  of  the  brain.  (Fig,  126.)     It  is  divided, 


Cerrbro-spina  L  System  of  Man. 
— 1.  Cerebrum.  2.  Cerebt-Uurn.  ^,^,'i.  Spinil 
cord  and  nerves.  4,  4.  Brachial  nerves 
S,  0.  Sacral  uorveB. 


380  GENERAL    STRUCTURE    AND    FUNCTIONS 

by  an  anterior  and  posterior  median  fissure,  into  two  lateral  halves, 
which  still  remain  connected  with  each  other  by  a  central  mass  or 
commissure.  Its  inner  portions  are  occupied  by  gray  matter, 
which  forms  a  continuous  ganglionic  chain,  running  from  one  ex- 
tremity of  the  cord  to  the  other.  Its  outer  portions  are  composed 
of  white  substance,  the  filaments  of  which  run  for  the  most  part  in 
a  longitudinal  direction,  connecting  the  different  parts  of  the  cord 
with  each  other,  and  the  cord  itself  with  the  ganglia  of  the  brain. 

The  spinal  nerves  are  given  off  from  the  spinal  cord  at  regular 
intervals,  and  in  symmetrical  pairs;  one  pair  to  each  successive 
portion  of  the  body.  Their  filaments  are  distributed  to  the  integu- 
ment and  muscles  of  the  corresponding  regions.  In  serpents,  where 
locomotion  is  performed  by  simple,  alternate,  lateral  movements 
of  the  spinal  column,  the  spinal  cord  and  its  nerves  are  of  the 
same  size  throughout.  But  in  the  other  vertebrate  classes,  where 
there  exist  special  organs  of  locomotion,  such  as  fore  and  hind 
legs,  wings,  and  the  like,  the  spinal  cord  is  increased  in  size  at 
the  points  where  the  nerves  of  these  organs  are  given  off;  and  the 
nerves  themselves,  which  supply  the  limbs,  are  larger  than  those 
originating  from  other  parts  of  the  spinal  cord.  Thus,  in  the  hu- 
man subject  (Fig.  126),  the  cervical  nerves,  which  go  to  the  arms, 
and  the  sacral  nerves,  which  are  distributed  to  the  legs,  are  larger 
than  the  dorsal  and  lumbar  nerves.  They  form,  also,  by  frequent 
inosculation,  two  remarkable  plexuses,  before  entering  their  corre- 
sponding limbs,  viz.,  the  bra- 

^'^'  ^'^'^' chial  plexus  above,  and  the 

sacral  plexus  below.  The 
cord  itself,  moreover,  pre- 
sents two  enlargements  at 
the  point  of  origin  of  these 
nerves,  viz.,  the  cervical  en- 
largement from  which  the 
brachial  nerves  (4,  4)  are 
given  off,  and  the  lumbar 

Transverse  Section  of  Spi.val  Cokj>. -a,b.  Spinal  enlargement  from  which  the 
nerves  of  right  and  left  sides,  showing  their  two  roots.  gacral  nerVCS  (s,  o)  Originate. 
tZ.  Origin  of  anterior  root.     «.  Origin  of  posterior  root.  __     ,  .       ,  ,   , 

c.  Ganglion  of  posterior  root.  If  the  spiual  cord  De  exa- 

mined in  transverse  section 
(Fig.  127),  it  will  be  seen  that  the  gray  matter  in  its  central  portion 
forms  a  double  crescentic-shaped  mass,  with  the  concavity  of  the 
crescents  turned  outward.     These  crescentic  masses  of  gray  matter, 


OF    THE    NERVOUS    SYSTEM.  381 

occupying  the  two  lateral  halves  of  the  cord,  are  united  with  each 
other  by  a  transverse  band  of  the  same  substance,  which  is  called 
the  gray  commissure  of  the  cord.  Directly  in  front  of  this  is  a  trans- 
verse band  of  white  substance,  connecting  in  a  similar  manner  the 
white  portions  of  the  two  lateral  halves.  It  is  called  the  white 
commissure  of  the  cord. 

The  spinal  nerves  originate  from  the  cord  on  each  side  by  two 
distinct  roots ;  one  anterior,  and  one  posterior.  The  anterior  root 
(Fig.  127,  d)  arises  from  the  surface  of  the  cord  near  the  extremity 
of  the  anterior  peak  of  gray  matter.  The  posterior  root  (e)  origi- 
nates at  the  point  corresponding  with  the  posterior  peak  of  gray 
matter.  Both  roots  are  composed  of  a  considerable  number  of 
ultimate  nervous  filaments,  united  with  each  other  in  parallel 
bundles.  The  posterior  root  is  distinguished  by  the  presence  of  a 
small  ganglion  (c),  which  appears  to  be  incorporated  with  it,  and 
through  which  its  fibres  pass.  There  is  no  such  ganglion  on  the 
anterior  root.  The  two  roots  unite  with  each  other  shortly  after 
leaving  the  cavity  of  the  spinal  canal,  and  mingle  their  filaments 
in  a  single  trunk. 

It  will  be  seen,  on  referring  to  the  diagram  (Fig.  127),  that  each 
lateral  half  of  the  spinal  cord  is  divided  into  two  portions,  an 
anterior  and  a  posterior  portion.  The  posterior  peak  of  gray  mat- 
ter comes  quite  up  to  the  surface  of  the  cord,  and  it  is  just  at  this 
point  (e)  that  the  posterior  roots  of  the  nerves  have  their  origin. 
The  whole  of  the  white  substance  included  between  this  point  and 
the  posterior  median  fissure  is  called  the  posterior  column  of  the 
cord.  That  which  is  included  between  the  same  point  and  the 
anterior  median  fissure  is  the  anterior  column  of  the  cord.  The 
white  substance  of  the  cord  may  then  be  regarded  as  consisting 
for  the  most  part  of  four  longitudinal  bundles  of  nervous  filaments, 
viz.,  the  right  and  left  anterior,  and  the  right  and  left  posterior 
columns.  The  posterior  median  fissure  penetrates  deeply  into  the 
substance  of  the  cord,  quite  down  to  the  gray  matter,  so  that  the 
posterior  columns  appear  entirely  separated  from  each  other  in  a 
transverse  section ;  while  the  anterior  median  fissure  is  more  shal- 
low and  stops  short  of  the  gray  matter,  so  that  the  anterior  columns 
are  connected  with  each  other  by  the  white  commissure  above  men- 
tioned. 

By  the  encephahn  we  mean  the  whole  of  that  portion  of  the 
cerebro-spinal  system  which  is  contained  in  the  cranial  cavity.  It 
is  divided  into  three  principal  parts,  viz.,  the  cerebrum,  cerebellum, 


382 


GENERAL   STRUCTURE    AND    FUNCTIONS 


Fig.  128. 


and  medulla  oblongata.  The  anatomy  of  these  parts,  though  some- 
what complicated,  can  be  readily  understood  if  it  be  recollected 
that  they  are  simply  a  double  series  of  nervous  ganglia,  connected  with 
each  other  and  with  the  spinal  cord  hy  transverse  and  longitudinal 
commissures.  The  number  and  relative  size  of  these  ganglia,  in 
different  kinds  of  animals,  depend  upon  the  perfection  of  the  bodily 
organization  in  general,  and  more  especially  on  that  of  the  intelli- 
gence and  the  special  senses.  They  are  most  readily  described  by 
commencing  with  the  simpler  forms  and  terminating  with  the  more 
complex. 

The  brain  of  the  Alligator  (Fig.  128)  consists  of  five  pair  of 
ganglia,  ranged  one  behind  the  other  in  the  interior  of  the  cranium. 
The  first  of  these  are  two  rounded  masses  (i),  lying  just  above  and 

behind  the  nasal  cavities,  which  distri- 
bute their  nerves  upon  the  Schneiderian 
mucous  membrane.  These  are  the  olfac- 
tory ganglia.  They  are  connected  with 
the  rest  of  the  brain  by  two  long  and 
slender  commissures,  the  "  olfactory  com- 
missures." The  next  pair  (2)  are  some- 
what larger  and  of  a  triangular  shape, 
when  viewed  from  above  downward. 
They  are  termed  the  "  cerebral  ganglia," 
or  the  hemispheres.  Immediately  follow- 
ing them  are  two  quadrangular  masses  (3) 
which  give  origin  to  the  optic  nerves,  and 
are  therefore  called  the  optic  ganglia. 
They  are  termed  also  the  "  optic  tuber- 
cles ;"  and  in  some  of  the  higher  animals, 
where  they  present  an  imperfect  division 
into  four  nearly  equal  parts,  they  are 
known  as  the  "  tubercula  quadrigemina." 
Behind  them,  we  have  a  single  triangular  collection  of  nervous 
matter  (4),  which  is  called  the  cerebellum.  Finally,  the  upper  por- 
tion of  the  cord,  just  behind  and  beneath  the  cerebellum,  is  seen  to 
be  enlarged  and  spread  out  laterally,  so  as  to  form  a  broad  oblong 
mass  (5),  the  medulla  oblongata.  It  is  from  this  latter  portion  of  the 
brain  that  the  pneumogastric  or  respiratory  nerves  originate,  and 
its  ganglia  are  therefore  sometimes  termed  the  "  pneumogastric"  or 
"  respiratory"  ganglia. 

It  will  be  seen  that  the  posterior  columns  of  the  cord,  as  they 


Brain  op  Alligator. —1.  Ol- 
factory ganglia.  2.  Heinispherps.  3. 
Optic  tubercles.  4.  Cerebellum.  5. 
Medulla  oblongata. 


OF    THE    NERVOUS    SYSTEM. 


383 


diverge  laterally  in  order  to  form  tlie  medulla  oblongata,  leave  be- 
tween them  an  open  space,  which  is  continuous  with  the  posterior 
median  fissure  of  the  cord.  This  space  is  known  as  the  ''  fourth 
ventricle."  It  is  partially  covered  in  by  the  backward  projection 
of  the  cerebellum,  but  in  the  alligator  is  still  somewhat  open  pos- 
teriorly, presenting  a  kind  of  chasm  or  gap  between  the  two  lateral 
halves  of  the  medulla  oblongata. 

The  successive  ganglia  which  compose  the  brain,  being  arranged 
in  pairs  as  above  described,  are  separated  from  each  other  on  the 
two  sides  by  a  longitudinal  median  fissure,  which  is  continuous 
with  the  posterior  median  fissure  of  the  cord.  In  the  brain  of  the 
alligator  this  fissure  appears  to  be  interrupted  at  the  cerebellum  ; 
but  in  the  higher  classes,  where  the  lateral  portions  of  the  cerebel- 
lum are  more  highly  developed,  as  in  the  human  subject  (Fig.  126), 
they  are  also  separated  from  each  other  posteriorly  on  the  median 
line,  and  the  longitudinal  median  fissure  is  complete  throughout. 

In  lirds,  the  hemispheres  are  of  much  larger  size  than  in  rep- 
tiles, and  partially  conceal  the  optic  ganglia.  The  cerebellum, 
also,  is  very  well  developed  in  this  class,  and  presents  on  its  sur- 
face a  number  of  transverse  foldings  or  convolutions  by  which 
the  quantity  of  gray  matter  which 
it  contains  is  considerably  in- 
creased. The  cerebellum  here 
extends  so  far  backward  as  almost 
completely  to  conceal  the  medulla 
oblongata  and  the  fourth  ven- 
tricle. 

In  the  quadrupeds,  the  hemis- 
pheres and  cerebellum  attain  a 
still  greater  size  in  proportion  to 
the  remaining  parts  of  the  brain. 
There  are  also  two  other  pairs  of 
ganglia,  situated  beneath  the  he- 
mispheres, and  between  them  and 
the  tubercula  quadrigemina. 
These  are  the  corpora  striata  in 
front  and  the  optic  thalami  behind. 
In  Fig.  129  is  shown  the  brain  of 
the  rabbit,  with  the  hemispheres 
laid  open  and  turned  aside,  so  as  to  show  the  internal  parts  in  their 
natural  situation.     The  olfactory  ganglia  are  seen  in  front  ( i )  con- 


Fig.  129. 


Brain  of  Rabbit,  viewed  from  above. — 
1.  Olfactory  ganglia.  2.  Hemisplieres,  turned 
aside.  3.  Corpora  Ktriata.  4.  Optic  thalami. 
6.  Tubercula  quadrigemina.     6.  Cerebellum. 


884 


GENERAL    STRUCTURE   AND    FUNCTIONS 


nected  with  tlie  remaining  parts  "by  tte  olfactory  commissures.  The 
separation  of  the  hemispheres  (2,  2)  shows  the  corpora  striata  (3)  and 
the  optic  thalami  (4).  Then  come  the  tubercula  quadrigemina  (5), 
which  are  here  composed,  as  above  mentioned,  of  four  rounded 
masses  nearly  equal  in  size.  The  cerebellum  (e)  is  considerably  en- 
larged by  the  development  of  its  lateral  portions,  and  shows  an 
abundance  of  transverse  convolutions.  It  conceals  from  view  the 
fourth  ventricle  and  most  of  the  medulla  oblongata. 

In  other  species  of  quadrupeds  the  hemispheres  increase  in  size 
so  as  to  project  entirely  over  the  olfactory  ganglia  in  front,  and  to 
cover  in  the  tubercula  quadrigemina  and  the  cerebellum  behind. 
The  surface  of  the  hemispheres  also  becomes  covered  with  nume- 
rous convolutions,  which  are  curvilinear  and  somewhat  irregular 
in  form  and  direction,  instead  of  being  transverse,  like  those  of  the 
cerebellum.  In  man,  the  development  of  the  hemispheres  reaches 
its  highest  point ;  so  that  they  preponderate  altogether  in  size  over 
the  rest  of  the  ganglia  constituting  the  brain.  In  the  human  brain, 
accordingly,  when  viewed  from  above  downward,  there  is  nothing 
to  be  seen  but  the  convex  surfaces  of  the  hemispheres ;  and  even 
in  a  posterior  view,  as  seen  in  Fig.  126,  they  conceal  everything 
but  a  portion  of  the  cerebellum.  All  the  remaining  parts,  how- 
ever, exist  even  here,  and  have  the  same  connections  and  relative 
situation  as  in  other  instances.  They  may 
best  be  studied  in  the  following  order. 

As  the  spinal  cord,  in  the  human  subject, 
passes  upward  into  the  cranial  cavity,  it  en- 
larges into  the  medulla  oblongata  as  already 
described.  The  medulla  oblongata  presents 
on  each  side  three  projections,  two  anterior 
and  one  posterior.  The  middle  projections 
on  its  anterior  surface  (Fig.  130,  1,  1),  which 
are  called  the  anterior  pyramids,  are  the  con- 
tinuation of  the  anterior  columns  of  the  cord. 
They  pass  onward,  underneath  the  transverse 
fibres  of  the  pons  Yarolii,  run  upward  to  the 
corpora  striata,  pass  through  these  bodies, 
and  radiate  upward  and  outward  from  their 
external  surface,  to  terminate  in  the  gray 
matter  of  the  hemispheres.  The  projections 
immediately  on  the  outside  of  the  anterior  pyramids,  in  the  medulla 
oblongata,  are  the  olivary  bodies  (2,  2).     They  contain  in  their  in- 


Fig.  130. 


Medulla  Oblonrata 
OF  HrMAN  Brain,  ante- 
rior view  — 1,  1.  Anterior  py- 
ramids. 2,  2.  Olivary  bodies. 
S,  3.  Bestirorm  bodies.  4.  De- 
cussation of  the  anterior  co- 
lumns. The  medalla  oblong- 
ata is  seen  terminated  above 
by  the  transverse  fibres  of  the 
pons  Varolii. 


OF    THE    NERVOUS    SYSTEif,  385 

terior  a  thin  layer  of  gray  matter  folded  upon  itself,  the  functions 
and  connections  of  which  are  but  little  understood,  and  are  not 
apparently,  of  very  great  importance. 

The  anterior  columns  of  the  cord  present,  at  the  lower  part  of  the 
medulla  oblongata,  a  remarkable  interchange  or  crossing  of  their 
fibres  (4).  The  fibres  of  the  left  anterior  column  pass  across  the 
median  line  at  this  spot,  and  becoming  continuous  with  the  right 
anterior  pyramid,  are  finally  distributed  to  the  right  side  of  the 
cerebrum ;  while  the  fibres  of  the  right  anterior  column,  passing 
over  to  the  left  anterior  pyramid,  are  distributed  to  the  left  side  of 
the  cerebrum.  This  interchange  or  crossing  of  the  nervous  fibres 
is  known  as  the  decussation  of  the  anterior  columns  of  the  cord. 

The  posterior  columns  of  the  cord,  as  they  diverge  on  each  side 
of  the  fourth  ventricle,  form  the  posterior  and  lateral  projections  of 
the  medulla  oblongata  (3,  3).  They  are  sometimes  called  the  "res- 
tiform  bodies,"  and  are  extremely  important  parts  of  the  brain. 
They  consist  in  great  measure  of  the  longitudinal  filaments  of 
the  posterior  columns,  which  pass  upward  and  outward,  and  are 
distributed  partly  to  the  gray  matter  of  the  cerebellum.  The 
remainder  then  pass  forward,  underneath  the  tubercula  quadri- 
gemina,  into  and  through  the  optic  thalami ;  and  radiating  thence 
upward  and  outward,  are  distributed,  like  the  continuation  of  the 
anterior  columns,  to  the  gray  matter  of  the  cerebrum.  The  resti- 
form  bodies,  however,  in  passing  upward  to  the  cerebellum,  are 
supplied  with  some  fibres  from  the  anterior  columns  of  the  cord, 
which,  leaving  the  lower  portion  of  the  anterior  pyramids,  join  the 
restiform  bodies,  and  are  distributed  with  them  to  the  cerebellum. 
From  this  description  it  will  be  seen  that  both  the  cerebrum  and 
the  cerebellum  are  supplied  with  filaments  from  both  the  anterior 
and  posterior  columns  of  the  cord. 

In  the  substance  of  each  restiform  body,  moreover,  there  is  im- 
bedded a  ganglion  which  gives  origin  to  the  pneumogastric  nerve, 
and  presides  over  the  functions  of  respiration.  This  ganglion  is 
surrounded  and  covered  by  the  longitudinal  fibres  passing  upward 
from  the  cord  to  the  cerebellum,  but  may  be  discovered  by  cutting 
into  the  substance  of  the  restiform  body,  in  which  it  is  buried.  It 
is  the  first  important  ganglion  met  with,  in  dissecting  the  brain 
from  below  upward. 

While  the  anterior  columns  are  passing  beneath  the  pons  Varolii, 
they  form,  together  with  the  continuation  of  the  posterior  columns 
and  the  transverse  fibres  of  the  pons  itself,  a  rounded  prominence 
25 


386 


GENERAL    STRUCTURE    AND    FUNCTIONS 


or  tuberosity,  which  is  known  by  the  name  of  the  tuber  annulare. 
In  the  deeper  portions  of  this  protuberance  there  is  situated,  among 
the  lono-itudinal  fibres,  another  collection  of  gray  matter,  which 
though  not  of  large  size,  has  very  important  functions  and  connec- 
tions.    This  is  known  as  the  ganglion  of  the  tuber  annulare. 

Situated  almost  immediately  above  these  parts  we  have  the  cor- 
pora striata  in  front,  and  the  optic  thalami  behind,  nearly  equal  in 
size,  and  giving  passage,  as  above  described,  to  the  fibres  of  the 
anterior  and  posterior  columns.  Behind  them  still,  and  on  a  little 
lower  level,  are  the  tubercula  quadrigemina,  giving  origin  to  the 
optic  nerves.  The  olfactory  ganglia  rest  upon  the  cribriform  plate 
of  the  ethmoid  bone,  and  send  the  olfactory  filaments  through  the 
perforations  in  this  plate,  to  be  distributed  upon  the  mucous  mem- 
brane of  the  upper  and  middle  turbinated  bones.  The  cerebellum 
covers  in  the  fourth  ventricle  and  the  posterior  surface  of  the 
medulla  oblongata ;  and  finally  the  cerebrum,  which  has  attained 
the  size  of  the  largest  ganglion  in  the  cranial  cavity,  extends  so  far 
in  all  directions,  forward,  backward,  and  laterally,  as  to  form  a  con- 
voluted arch  or  vault,  completely  covering  all  the  remaining  parts 
of  the  encephalon. 

The  entire  brain  may  tlierefore  be  regarded  as  a  connected  series 

of  ganglia,  the  arrangement  of 
which  is  shown  in  the  accompany- 
ing diagram.  (Fig.  131.)  These 
ganglia  occur  in  the  following 
order,  counting  from  before  back- 
ward: 1st.  The  olfactory  gan- 
glia. 2d.  The  cerebrum  or  hemi- 
spheres. 3d.  The  corpora  striata. 
4th.  The  optic  thalami.  oth.  The 
tubercula  quadrigemina.  6th. 
The  cerebellum.  7th.  The  gan- 
glion of  the  tuber  annulare.  And 
8th.  The  ganglion  of  the  medulla 
oblongata.  Of  these  ganglia, 
only  the  hemispheres  and  cere- 
bellum are  convoluted,  while  the 
remainder  are  smooth  and  round- 
ed or  somewhat  irregular  in 
shape.  The  course  of  the  fibres 
coming  from  the  anterior  and  posterior  columns  of  the  cord  is  also 


Fig.  131. 


Diagram  ofHoMAS  Brain,  in  vertical  sec- 
tion; showing  the  situation  of  the  different  gan- 
glia, and  the  course  of  the  fibres.  1.  Olfactory 
ganglion.  2.  Hemisphere.  3.  Corpus  striatum. 
4.  Optic  thalamus.  5,  Tubercula  quadrigemina. 
6.  Cerebellum.  7.  Ganglion  of  tuber  annulare. 
8.  Ganglion  of  medulla  oblongata. 


OF    THE    NERVOUS    SYSTEM.  387 

to  be  seen  in  the  accompanying  figure.  A  portion  of  the  anterior 
fibres,  we  have  already  observed,  pass  upward  and  backward,  with 
the  restiform  bodies,  to  the  cerebellum ;  while  the  remainder  run 
forward  through  the  tuber  annulare  and  the  corpus  striatum,  and 
then  radiate  to  the  gray  matter  of  the  cerebrum.  The  posterior 
fibres,  constituting  the  restiform  body,  are  distributed  partly  to  the 
cerebellum,  and  then  pass  forward,  as  previously  described,  under- 
neath the  tubercula  quadrigemina  to  the  optic  thalmi,  whence  they 
are  also  finally  distributed  to  the  gray  matter  of  the  cerebrum. 

The  cerebrum  and  cerebellum,  each  of  which  is  divided  into  two 
lateral  halves  or  "  lobes,"  by  the  great  longitudinal  fissure,  are  both 
provided  with  transverse  commissures,  by  which  a  connection  is 
established  between  their  right  and  left  sides.  The  great  trans- 
verse commissure  of  the  cerebrum  is  that  layer  of  white  substance 
which  is  situated  at  the  bottom  of  the  longitudinal  fissure,  and 
which  is  generally  known  by  the  name  of  the  "  corpus  callosum." 
It  consists  of  nervous  filaments,  which  originate  from  the  gray 
matter  of  one  hemisphere,  converge  to  the  centre,  where  they  be- 
come parallel,  cross  the  median  line,  and  are  finally  distributed  to 
the  corresponding  parts  of  the  hemisphere  upon  the  opposite  side. 
The  transverse  commissure  of  the  cerebellum  is  the  pons  Varolii. 
Its  fibres  converge  from  the  gray  matter  of  the  cerebellum  on  one 
side,  and  pass  across  to  the  opposite ;  encircling  the  tuber  annulare 
with  a  band  of  parallel  curved  fibres,  to  which  the  name  of  "  pons 
Varolii"  has  been  given  from  their  resemblance  to  an  arched  bridge. 

The  cerebro-spinal  system,  therefore,  consists  of  a  series  of  gan- 
glia situated  in  the  cranio-spinal  cavities,  connected  with  each  other 
by  transverse  and  longitudinal  commissures,  and  sending  out  nerves 
to  the  corresponding  parts  of  the  body.  The  spinal  cord  supplies 
the  integument  and  muscles  of  the  neck,  trunk,  and  extremities ; 
while  the  ganglia  of  the  brain,  besides  supplying  the  corresponding 
parts  of  the  head,  preside  also  over  the  organs  of  special  sense,  and 
perform  various  other  functions  of  a  purely  nervous  character. 


388  OF    NEBVOUS   IRRITABILITY 


CHAPTER    II. 

OF   NERVOUS  IRRITABILITY  AND   ITS  MODE    OF 

ACTION. 

We  have  already  mentioned,  in  a  previous  chapter,  that  every 
organ  in  the  body  is  endowed  with  the  property  of  irritability  ;  that 
is,  the  property  of  reacting  in  some  peculiar  manner  when  subjected 
to  the  action  of  a  direct  stimulus.  Thus  the  irritability  of  a  gland 
shows  itself  by  increased  secretion,  that  of  the  capillary  vessels  by 
congestion,  that  of  the  muscles  by  contraction.  Now  the  irritability 
of  the  muscles,  indicated  as  above  by  their  contraction,  is  extremely 
serviceable  as  a  means  of  studying  and  exhibiting  nervous  pheno- 
mena. We  shall  therefore  commence  this  chapter  by  a  study  of 
some  of  the  more  important  facts  relating  to  muscular  irritability. 

Tlie  irritability  of  the  muscles  is  a  j^roperty  inherent  in  the  muscular 
fibre  itself.  The  existence  of  muscular  irritability  cannot  be  ex- 
plained by  any  known  physical  or  chemical  laws,  so  far  as  they 
relate  to  inorganic  substances.  It  must  be  regarded  simply  as  a 
peculiar  property,  directly  dependent  on  the  structure  and  consti- 
tution of  the  muscular  fibre ;  just  as  the  property  of  emitting  light 
belongs  to  phosphorus,  or  that  of  combining  with  metals  to  oxygen. 
This  property  may  be  called  into  action  by  various  kinds  of  stimu- 
lus ;  as  by  pinching  the  muscular  fibre,  or  pricking  it  with  the  point 
of  a  needle,  the  application  of  an  acid  or  alkaline  solution,  or  the 
discharge  of  a  galvanic  battery.  All  these  irritating  applications 
are  immediately  followed  by  contraction  of  the  muscular  fibre. 
This  contraction  will  even  take  place  under  the  microscope,  when 
the  fibre  is  entirely  isolated,  and  removed  from  contact  with  any 
other  tissue ;  showing  that  the  properties  of  contraction  and  irrita- 
bility reside  in  the  fibre  itself,  and  are  not  communicated  to  it  by 
other  parts. 

Muscular  irritability  continues  for  a  certain  time  after  death.  The 
stoppage  of  respiration  and  circulation  does  not  at  once  destroy 
the  vital  properties  of  the  tissues,  but  nearly  all  of  them  retain 


AN'D    ITS    IIODE    OF    ACTION. 


389 


these  properties  to  a  certain  extent  for  some  time  afterward.  It  is 
only  when  the  constitution  of  the  tissues  has  become  altered  hy 
being  deprived  of  blood,  and  by  the  consequent  derangement  of 
the  nutritive  process,  that  their  characteristic  properties  are  finally 
lost.  Thus,  in  the  muscles,  irritability  and  contractility  may  be 
easily  shown  to  exist  for  a  short  time  after  death  by  applying  to 
the  exposed  muscular  fibre  the  same  kind  of  stimulus  that  we  have 
already  found  to  affect  it  during  life.  It  is  easy  to  see,  in  the 
muscles  of  the  ox,  after  the  animal  has  been  killed,  flayed,  and 
eviscerated,  different  bundles  of  muscular  fibres  contracting  irregu- 
larly for  a  long  time,  where  they  are  exposed  to  the  contact  of  the 
air.  Eyen  in  the  human  subject  the  same  phenomenon  may  be 
seen  in  cases  of  amputation ;  the  exposed  muscles  of  the  amputated 
limb  frequently  twitching  and  quivering  for  many  minutes  after 
their  separation  from  the  body. 

The  duration  of  muscular  irritability,  after  death,  varies  consider- 
ably in  different  classes  of  animals.  It  disappears  most  rapidly 
in  those  whose  circulation  and  respiration  are  naturally  the  most 
active ;  while  it  continues  for  a  longer  time  in  those  whose  circula- 
tion and  respiration  are  sluggish.  Thus  in  birds  the  muscular 
irritability  continues  only  a  few  minutes  after  the  death  of  the 
animal.  In  quadrupeds  it  lasts  somewhat  longer ; 
while  in  reptiles  it  remains,  under  favorable  cir- 
cumstances, for  many  hours.  The  cause  of  this 
difference  is  probably  that,  in  birds  and  quadrupeds, 
the  tissues  being  very  vascular,  and  the  molecular 
changes  of  nutrition  going  on  with  rapidity,  the 
constitution  of  the  muscular  fibre  becomes  so 
rapidly  altered  after  the  circulation  has  ceased, 
that  its  irritability  soon  disappears.  In  reptiles, 
on  the  other  hand,  the  tissues  are  less  vascular 
than  in  birds  and  quadrupeds,  and  all  the  nutritive 
changes  go  on  more  slowly.  Eespiration  and  cir- 
culation can  therefore  be  dispensed  with  for  a  longer 
period,  before  the  constitution  of  the  tissues  be- 
comes so  much  altered  as  to  destroy  altogether 
their  vital  properties. 

Owing  to  this  peculiarity  of  the  cold-blooded 
animals,  their  tissues  may  be  used  with  great  ad- 
vantage for  purposes  of  experiment.     If  a  frog's  leg,  for  example, 
be  separated  from  the  body  of  the  animal  (Fig.  1B2),  the  skin 


Fig.  132. 


Frog's  Lr,o,  with 
poles  of  galvauic  bat- 
tery applied  to  the 
muscles  at  a,  b. 


3y0  -  OF    NERVOUS    IRRITABILITY 

removed,  and  the  poles  of  a  galvanic  apparatus  applied  to  tlie  sur- 
face of  the  muscle  (a,  /;),  a  contraction  takes  place  every  time  the 
circuit  is  completed  and  a  discharge  passed  through  the  tissues  of 
the  limb.  The  leg  of  the  frog,  prepared  in  this  way,  may  be  em- 
ployed for  a  long  time  for  the  purpose  of  exhibiting  the  effect  of 
various  kinds  of  stimulus  upon  the  muscles.  All  the  mechanical 
and  chemical  irritants  which  we  have  mentioned,  pricking,  pinching, 
cauterization,  galvanism,  &c.,  act  with  more  or  less  energy  and 
promptitude,  though  the  most  efficient  of  all  is  the  electric  discharge. 

Continued  irritation  exhausts  the  irritahility  of  the  muscles.  It  is 
found  that  the  irritability  of  the  muscles  wears  out  after  death  more 
rapidly  if  they  be  artificially  excited,  than  if  they  be  allowed  to 
remain  at  rest.  During  life,  the  only  habitual  excitant  of  mus- 
cular contraction  is  the  peculiar  stimulus  conveyed  by  the  nerves. 
After  death  this  stimulus  may  be  replaced  or  imitated,  to  a  certain 
extent,  by  other  irritants ;  but  their  application  gradually  exhausts 
the  contractility  of  the  muscle  and  hastens  its  final  disappearance. 
Under  ordinary  circumstances,  the  post-mortem  irritability  of  the 
muscle  remains  until  the  commencement  of  cadaveric  rigidity. 
"When  this  has  become  fairly  established,  the  muscles  will  no  longer 
contract  under  the  application  of  an  artificial  stimulus. 

Certain  poisonous  substances  have  the  power  of  destroying  the 
irritability  of  the  muscles  by  a  direct  action  upon  their  tissue. 
Sulphocyanide  of  potassium,  for  example,  introduced  into  the  cir- 
culation in  sufficient  quantity  to  cause  death,  destroys  entirely  the 
muscular  irritability,  so  that  no  contraction  can  afterward  be  pro- 
duced by  the  application  of  an  external  stimulant. 

Nervous  Irritahility. — The  irritability  of  the  nerves  is  the  pro- 
perty by  which  they  may  be  excited  by  an  external  stimulus,  so  as 
to  be  called  into  activity  and  excite  in  their  turn  other  organs  to 
which  their  filaments  are  distributed.  When  a  nerve  is  irritated, 
therefore,  its  power  of  reaction,  or  its  irritability,  can  only  be  esti- 
mated by  the  degree  of  excitement  produced  in  the  organ  to  which 
the  nerve  is  distributed.  A  nerve  running  from  the  integument  to 
the  brain  produces,  when  irritated,  a  painful  sensation;  one  dis- 
tributed to  a  glandular  organ  produces  increased  secretion ;  one  dis- 
tributed to  a  muscle  produces  contraction.  Of  all  these  effects, 
muscular  contraction  is  found  to  be  the  best  test  and  measure  of 
nervous  irritability,  for  purposes  of  experiment.  Sensation  cannot 
of  course  be  relied  on  for  this  purpose,  since  both  consciousness  and 
volition  are  abolished  at  the  time  of  death.     The  activity  of  the 


AND    ITS    MODE    OF    ACTION. 


891 


Fig.  133. 


glandular  organs,  owing  to  the  stoppage  of  the  circulation,  disappears 
also  very  rapidly,  or  at  least  cannot  readily  be  demonstrated.  The 
contractility  of  the  muscles,  however,  lasts,  as  we  have  seen,  for  a 
considerable  time  after  death,  and  may  accordingly  be  employed 
■with  great  readiness  as  a  test  of  nervous  irritability.  The  manner 
of  its  employment  is  as  follows : — 

The  leg  of  a  frog  is  separated  from  the  body  and  stripped  of  its 
integument;  the  sciatic  nerve  having  been  previously  dissected 
out  and  cut  off'  at  its  point  of  emergence  from  the 
spinal  canal,  so  that  a  considerable  portion  of  it 
remains  in  connection  with  the  separated  limb. 
(Fig.  133.)  If  the  two  poles  of  a  galvanic  appa- 
ratus be  now  placed  in  contact  with  different 
points  (a  b)  of  the  exposed  nerve,  and  a  discharge 
allowed  to  pass  between  them,  at  the  moment 
of  discharge  a  sudden  contraction  takes  place  in 
the  muscles  below.  It  will  be  seen  that  this  ex- 
periment is  altogether  different  from  the  one  re- 
presented in  Fig.  132.  In  that  experiment  the 
galvanic  discharge  passes  through  the  muscles 
themselves,  and  acts  upon  them  by  direct  stim- 
ulus. Here,  however,  the  discharge  passes  only 
from  a  to  6  through  the  tissues  of  the  nerve,  and 
acts  directly  upon  the  nerve  alone ;  while  the 
nerve,  acting  upon  the  muscles  by  its  own  pecu- 
liar agency,  causes  in  this  way  a  muscular  con- 
traction. It  is  evident  that  in  order  to  produce 
this  effect,  two  conditions  are  equally  essential :  1st. 
The  irritability  of  the  muscles ;  and  2d.  The  irri- 
tability of  the  nerve.  So  long,  therefore,  as  the 
muscles  are  in  a  healthy  condition,  their  contraction,  under  the 
influence  of  a  stimulus  applied  to  the  nerve,  demonstrates  the  irri- 
tability of  the  latter,  and  may  be  used  as  a  convenient  measure  of 
its  intensity. 

Tlie  irritability  of  the  nerve  continues  after  death.  The  knowledge 
of  this  fact  follows  from  what  has  just  been  said  with  regard  to  ex- 
perimenting upon  the  frog's  leg,  prepared  as  above.  The  irrita- 
bility of  the  nerve,  like  that  of  the  muscle,  depends  directly  upon 
its  anatomical  structure  and  constitution ;  and  so  long  as  these  re- 
main unimpaired,  the  nerve  will  retain  its  vital  properties,  though 
respiration  and  circulation  may  have  ceased.     For  the  same  reason, 


Frog's  Leo,  with 
sciatic  neive  (N)  at- 
tached.— a  b.  Poles  of 
galvanic  battery,  ap- 
plied to  nerve. 


392  OF    NERVOUS    IRRITABILITY 

also,  as  that  given  above  with  regard  to  the  muscles,  nervous  irri- 
tability lasts  much  longer  after  death  in  the  cold-blooded  than  in 
the  warm-blooded  animals.  Various  artificial  irritants  may  be  em- 
ployed to  call  it  into  activity.  Pinching  or  pricking  the  exposed 
nerve  with  steel  instruments,  the  application  of  caustic  liquids,  and 
the  passage  of  galvanic  discharges,  all  have  this  effect.  The  electric 
current,  however,  is  much  the  best  means  to  employ  for  this  pur- 
pose, since  it  is  more  delicate  in  its  operation  than  the  others,  and 
will  continue  to  succeed  for  a  longer  time. 

The  nerve  is,  indeed,  so  exceedingly  sensitive  to  the  electric  cur- 
rent, that  it  will  respond  to  it  when  insensible  to  all  other  kinds  of 
stimulus.  A  frog's  leg  freshly  prepared  with  the  nerve  attached, 
as  in  Fig.  133,  will  react  so  readily  whenever  a  discharge  is  passed 
through  the  nerve,  that  it  forms  an  extremely  delicate  instrument 
for  detecting  the  presence  of  electric  currents  of  low  intensity,  and 
has  even  been  used  for  this  purpose  by  Matteucci,  under  the  name 
of  the  "  galvanoscopic  frog."  It  is  only  necessary  to  introduce  the 
nerve  as  part  of  the  electric  circuit ;  and  if  even  a  very  feeble  cur- 
rent be  present,  it  is  at  once  betrayed  by  a  muscular  contraction. 

The  superiority  of  electricity  over  other  means  of  exciting  nerv- 
ous action,  such  as  mechanical  violence  or  chemical  agents,  pro- 
bably depends  upon  the  fact  that  the  latter  necessarily  alter  and 
disintegrate  more  or  less  the  substance  of  the  nerve,  so  that  its  irri- 
tability soon  disappears.  The  electric  current,  on  the  other  hand, 
excites  the  nervous  irritability  without  any  marked  injury  to  the 
substance  of  the  nervous  fibre.  Its  action  may,  therefore,  be  con- 
tinued for  a  longer  period. 

Nervous  irritability,  like  that  of  the  muscles,  is  exhausted  by  repeated 
excitement.  If  a  frog's  leg  be  prepared  as  above,  with  the  sciatic 
nerve  attached,  and  allowed  to  remain  at  rest  in  a  damp  and  cool 
place,  where  its  tissue  will  not  become  altered  by  desiccation,  the 
nerve  will  remain  irritable  for  many  hours ;  but  if  it  be  excited, 
soon  after  its  separation  from  the  body,  by  repeated  galvanic  shocks, 
it  soon  begins  to  react  with  diminished  energy,  and  becomes  gra- 
dually less  and  less  irritable,  until  it  at  last  ceases  to  exhibit  any 
further  excitability.  If  it  be  now  allowed  to  remain  for  a  time  at 
rest,  its  irritability  will  be  partially  restored ;  and  muscular  contrac- 
tion will  again  ensue  on  the  application  of  a  stimulus  to  the  nerve. 
Exhausted  a  second  time,  and  a  second  time  allowed  to  repose,  it 
will  again  recover  itself;  and  this  may  even  be  repeated  several 
times  in  succession.     At  each  repetition,  however,  the  recovery  of 


AND    ITS    MODE    OF    ACTION.  393 

nervous  irritability  is  less  complete,  until  it  finally  disappears  alto- 
gether, and  can  no  longer  be  recalled. 

Various  accidental  circumstances  tend  to  diminish  or  destroy 
nervous  irritability.  The  action  of  the  woorara  poison,  for  example, 
destroys  at  once  the  irritability  of  the  nerves ;  so  that  in  animals 
killed  by  this  substance,  no  muscular  contraction  takes  place  on 
irritating  the  nervous  trunk.  Severe  and  sudden  mechanical  inju- 
ries often  have  the  same  effect ;  as  where  death  is  produced  by 
violent  and  extensive  crushing  or  laceration  of  the  body  or  limbs. 
Such  an  injury  produces  a  general  disturbance,  or  shoch  as  it  is 
called,  which  affects  the  entire  nervous  system,  and  destroys  oi 
suspends  its  irritability.  The  effects  of  such  a  nervous  shock  may 
frequently  be  seen  in  the  human  subject  after  railroad  accidents, 
where  the  patient,  though  very  extensively  injured,  may  remain 
for  some  hours  without  feeling  the  pain  of  his  wounds.  It  is  only 
after  reaction  has  taken  place,  and  the  activity  of  the  nerves  has 
been  restored,  that  the  patient  begins  to  be  sensible  of  pain. 

It  will  often  be  found,  on  preparing  the  frog's  leg  for  experiment 
as  above,  that  immediately  after  the  limb  has  been  separated  from 
the  body  and  the  integument  removed,  the  nerve  is  destitute  of 
irritability.  Its  vitality  has  been  suspended  by  the  violence  in- 
flicted in  the  preparatory  operation.  In  a  few  moments,  however, 
if  kept  under  favorable  conditions,  it  recovers  from  the  shock,  and 
regains  its  natural  irritability. 

The  action  of  the  galvanic  current  upon  the  nerves,  as  first  shown 
by  the  experiments  of  Matteucci,  is  in  many  respects  peculiar.  If 
the  current  be  made  to  traverse  the  nerve  in  the  natural  direction 
of  its  fibres,  viz.,  from  its  origin  towards  its  distribution,  as  from  a 
to  h  in  Fig.  133,  it  is  called  the  direct  current.  If  it  be  made  to 
pass  in  the  contrary  direction,  as  from  h  to  a,  it  is  called  the  inverse 
current.  When  the  nerve  is  fresh  and  exceedingly  irritable,  a 
mascular  contraction  takes  place  at  both  the  commencement  and 
termination  of  the  current,  whether  it  be  direct  or  inverse.  But 
very  soon  afterward,  when  the  activity  of  the  nerve  has  become 
somewhat  diminished,  it  will  be  found  that  contraction  takes  place 
only  at  the  commencement  of  the  direct  and  at  the  termination  of  the 
inverse  current.  This  may  readily  be  shown  by  preparing  the  two 
legs  of  the  same  frog  in  such  a  manner  that  they  remain  connected 
with  each  other  by  the  sciatic  nerves  and  that  portion  of  the  spinal 
column  from  which  these  nerves  take  their  origin.  The  two  legs, 
so  prepared,  should  be  placed  each  in  a  vessel  of  water,  with  the 


394 


OF    NERVOUS   IRRITABILITY 


nervous  connection  hanging  between.  (Fig.  134.)  If  the  positive 
pole,  a,  of  the  battery  be  now  placed  in  the  vessel  which  holds  leg 
No.  1,  and  the  negative  pole,  h,  in  that  containing  leg  No.  2,  it  will 
be  seen  that  the  galvanic  current  will  traverse  the  two  legs  in  op- 
posite directions.  In  No.  1,  it  will  pass  in  a  direction  contrary  to 
the  course  of  its  nervous  fibres,  that  is,  it  will  be  for  this  leg  an 

Fiff.  134. 


inverse  current ;  while  in  No.  2  it  will  pass  in  the  same  direction 
with  that  of  the  nervous  fibres,  that  is,  it  will  be  for  this  \Qg  a  direct 
current.  It  will  now  be  found  that  at  the  moment  when  the  cir- 
cuit is  completed,  a  contraction  takes  place  in  No.  2  by  the  direct 
current,  while  No.  1  remains  at  rest ;  but  at  the  time  the  circuit  is 
broken,  a  contraction  is  produced  in  No.  1  by  the  inverse  current, 
but  no  movement  takes  place  in  No.  2.  A  succession  of  alternate 
contractions  may  thus  be  produced  in  the  two  legs  by  repeatedly 
closing  and  opening  the  circuit.  If  the  position  of  the  poles,  a,  h, 
be  reversed,  the  efi:'ects  of  the  current  will  be  changed  in  a  corre- 
sponding manner. 

After  a  nerve  has  become  exhausted  by  the  direct  current,  it  is 
still  sensitive  to  the  inverse ;  and  after  exhaustion  by  the  inverse, 
it  is  still  sensitive  to  the  direct.  It  has  even  been  found  by  Mat- 
teucci  that  after  a  nerve  has  been  exhausted  for  the  time  by  the  direct 
current,  the  return  of  its  irritability  is  hastened  by  the  subsequent 
passage  of  the  inverse  current ;  so  that  it  will  become  again  sensi- 
tive to  the  direct  current  sooner  than  if  allowed  to  remain  at  rest. 
Nothing,  accordingly,  is  so  exciting  to  a  nerve  as  the  passage  of 
direct  and  inverse  currents,  alternating  with  each  other  in  rapid 
succession.     Such  a  mode  of  applying  the  electric  stimulus  is  that 


AND   ITS    MODE    OF    ACTION.  895 

usually  adopted  in  the  galvanic  machines  used  in  medical  practice, 
for  the  treatment  of  certain  paralytic  affections.  In  these  machines, 
the  electric  circuit  is  alternately  formed  and  broken  with  great 
rapidity,  thus  producing  the  greatest  effect  upon  the  nerves  with 
the  smallest  expenditure  of  electricity.  Such  alternating  currents, 
however,  if  very  powerful,  exhaust  the  nervous  irritability  more 
rapidly  and  completely  than  any  other  kind  of  irritation ;  and  in 
an  animal  killed  by  the  action  of  a  battery  used  in  this  manner,  the 
nerves  may  be  found  to  be  entirely  destitute  of  irritability  from  the 
moment  of  death. 

The  irritability  of  the  nerves  is  distinct  from  that  of  the  muscles;  and 
the  two  may  be  destroyed  or  suspended  independently  of  each  other. 
When  the  frog's  leg  has  been  prepared  and  separated  from  the 
body,  with  the  sciatic  nerve  attached,  the  muscles  contract,  as  we 
have  seen,  whenever  the  nerve  is  irritated.  The  irritability  of  the 
nerve,  therefore,  is  manifested  in  this  instance  only  through  that  of 
the  muscle,  and  that  of  the  muscle  is  called  into  action  only  through 
that  of  the  nerve.  The  two  properties  may  be  separated  from  each 
other,  however,  by  the  action  of  woorara,  which  has  the  power,  as 
first  pointed  out  by  Bernard,  of  destroying  the  irritability  of  the 
nerve  without  affecting  that  of  the  muscles.  If  a  frog  be  poisoned 
by  this  substance,  and  the  leg  prepared  as  above,  the  poles  of  a 
galvanic  battery  applied  to  the  nerve  will  produce  no  effect ;  show- 
ing that  the  nervous  irritability  has  ceased  to  exist.  But  if  the 
galvanic  discharge  be  passed  directly  through  the  muscles,  contrac- 
tion at  once  takes  place.  The  muscular  irritability  has  survived 
that  of  the  nerves,  and  must  therefore  be  regarded  as  essentially 
distinct  from  it. 

It  will  be  recollected,  on  the  other  hand,  that  in  cases  of  death 
from  the  action  of  sulphocyanide  of  potassium,  the  muscular  irri- 
tability is  itself  destroyed ;  so  that  no  contractions  occur,  even  when 
the  galvanic  discharge  is  made  to  traverse  the  muscular  tissue. 

There  are,  therefore,  two  kinds  of  paralysis :  first,  a  muscular 
paralysis,  in  which  the  muscular  fibres  themselves  are  directly 
affected ;  and  second,  a  nervous  paralysis,  in  which  the  affection  is 
confined  to  the  nervous  filaments,  the  muscles  retaining  their  natural 
properties,  and  being  still  capable  of  contracting  under  the  influence 
of  a  direct  stimulus. 

Nature  of  the  Nervous  Force. — The  special  endowment  by  which 
a  nerve  acts  and  manifests  its  vitality  is  a  peculiar  one,  inherent  in 
the  anatomical  structure  and  constitution  of  the  nervous  tissue.  It  is 


896  OF    NERVOUS    IRRITABILITY 

manifested,  in  tlie  foregoing  experiments,  by  its  effect  upon  the  con- 
tractile muscles.  But  we  shall  hereafter  see  that  this  is,  in  reality, 
only  one  of  its  results,  and  that  it  shows  itself,  during  life,  by  a 
variety  of  other  influences.  Thus  it  produces,  in  one  case,  sensa- 
tion ;  in  another,  muscular  contraction ;  in  another,  increased  or 
modified  glandular  activity;  in  another,  alterations  in  the  pheno- 
mena of  the  circulation.  The  force,  however,  which  is  exerted  by 
a  nerve  in  a  state  of  activity,  and  which  brings  about  these  changes, 
is  not  directly  appreciable  in  any  way  by  the  senses,  and  can  be 
judged  of  only  by  its  secondary  effects.  We  understand  enough 
of  its  mode  of  operation,  to  know  that  it  is  not  identical  with  the 
forces  of  chemical  affinity,  of  mechanical  action,  or  of  electricity. 

And  yet,  by  acting  upon  the  organs  to  which  the  nerves  are 
distributed,  it  will  finally  produce  phenomena  of  all  these  different 
kinds.  By  the  intervention  of  the  muscles,  it  results  in  mechanical 
action;  and  by  its  influence  upon  the  glands  and  bloodvessels,  it 
causes  chemical  alterations  in  the  animal  fluids  of  the  most  import- 
ant character. 

It  will  even  produce  well-marked  electrical  phenomena,  which 
in  some  cases  are  so  decided,  as  to  have  long  attracted  the  attention 
of  physiologists. 

It  has  been  fully  demonstrated  that  certain  fish  (gymnotus  and 
torpedo)  have  the  power  of  generating  electricity,  and  of  producing 
electric  discharges,  which  are  often  sufficiently  powerful  to  kill 
small  animals  that  may  come  within  their  reach.  That  the  force 
generated  by  these  animals  is  in  reality  electricity,  is  beyond  a 
doubt.  It  is  conducted  by  the  same  bodies  which  serve  as  con- 
ductors for  electricity,  and  is  stopped  by  those  which  are  non-con- 
ductors of  the  same.  All  the  ordinary  phenomena  produced  bj 
the  electric  current,  viz :  the  heating  and  melting  of  a  fine  con- 
ducting wire,  the  induction  of  secondary  currents  and  of  magnetism, 
the  decomposition  of  saline  solutions,  and  even  the  electric  spark, 
have  all  been  produced  by  the  force  generated  by  these  animals. 
There  is,  accordingly,  no  room  for  doubt  as  to  its  nature. 

The  electrical  phenomena,  in  these  cases,  are  produced  by  certain 
organs  which  are  called  into  activity  by  the  nervous  influence. 

The  electrical  organs  of  the  gymnotus  and  torpedo  occupy  a  con- 
siderable portion  of  the  body,  and  are  largely  supplied  with  nerves 
which  regulate  their  function.  If  these  nerves  be  divided,  tied,  or 
injured  in  any  way,  the  electrical  organ  is  weakened  or  paralyzed, 
just  as  the  muscles  would  suffer  if  the  nerves  distributed  to  them 


AND   ITS    MODE    OF    ACTION.  397 

were  subjected  to  a  similar  violence.  The  electricity  produced  by 
these  animals,  accordingly,  is  not  supplied  by  the  nerves,  but  by  a 
special  generating  organ,  the  action  of  which  is  regulated  by  nerv- 
ous influence. 

Moreover,  the  experiments  of  Longet  and  Matteucci^  have  shown 
that  no  electrical  current  is  to  be  detected  in  a  living  nerve,  even 
when  in  a  state  of  activity.  The  electrical  phenomenon,  when  it 
exists,  is  only  a  secondary  effect,  and  is  not  the  active  force  residing 
in  the  nervous  tissue.  This  force  is  special  in  its  nature,  and  is 
regulated  by  laws  peculiar  to  itself. 

'  Longet,  Traite  de  Physiologie.     Paris,  1850,  vol.  ii.  p.  130. 


398  THE    SPINAL    COED. 


CHAPTER    III. 

THE    SPINAL    CORD. 

We  have  already  seen  that  the  spinal  cord  is  a  long  ganglion, 
covered  with  longitudinal  bundles  of  nervous  filaments,  and  occu- 
pying the  cavity  of  the  spinal  canal.  It  sends  out  nerves  which 
supply  the  muscles  and  integument  of  at  least  nine-tenths  of  the 
whole  body,  viz.,  those  of  the  neck,  trunk,  and  extremities.  All 
these  parts  of  the  body  are  endowed  with  two  very  remarkable 
properties,  the  exercise  of  which  depends,  directly  or  indirectly, 
upon  the  integrity  and  activity  of  the  spinal  cord,  viz.,  the  power 
of  sensation  and  the  power  of  motion.  Both  these  properties  are 
said  to  reside  in  the  nervous  system,  because  they  are  so  readily 
influenced  by  its  condition,  and  are  so  closely  connected  with  its 
physiological  action.  We  shall  therefore  commence  the  study  of 
the  spinal  cord  with  an  examination  of  these  two  functions,  and  of 
the  situation  which  they  occupy  in  the  nervous  system. 

Sensation. — The  power  of  sensation,  or  sensibility,  is  the  power 
by  which  we  are  enabled  to  receive  impressions  from  external 
objects.  These  impressions  are  usually  of  such  a  nature  that  we 
can  derive  from  them  some  information  in  regard  to  the  qualities 
of  external  objects  and  the  effect  which  they  may  produce  upon 
our  own  systems.  Thus,  by  bringing  a  foreign  body  into  contact 
with  the  skin,  we  feel  that  it  is  hard  or  soft,  rough  or  smooth,  cold 
or  warm.  We  can  distinguish  the  separate  impressions  produced 
by  several  bodies  of  a  similar  character,  and  we  can  perceive  whe- 
ther either  one  of  them,  while  in  contact  with  the  skin,  be  at  rest 
or  in  motion.  This  power,  which  is  generally  distributed  over  the 
external  integument,  is  dependent  on  the  nervous  filaments  rami- 
fying in  its  tissue.  For  if  the  nerves  distributed  to  any  part  of  the 
body  be  divided,  the  power  of  sensation  in  the  corresponding  region 
is  immediately  lost. 


SENSATION.  399 

The  sensibility,  thus  distributed  over  the  integument,  varies  in 
its  acuteness  in  different  parts  of  the  body.  Thus,  the  extremities 
of  the  fingers  are  more  sensitive  to  external  impressions  than  the 
general  surface  of  the  limbs  and  trunk.  The  surfaces  of  the  fingers 
which  lie  in  contact  with  each  other  are  more  sensitive  than  their 
dorsal  or  palmar  surfaces.  The  point  of  the  tongue,  the  lips,  and 
the  orifices  of  most  of  the  mucous  passages  are  endowed  with  a 
sensibility  which  is  more  acute  than  that  of  the  general  integument. 

If  the  impression  to  which  these  parts  are  subjected  be  harsh  or 
violent  in  its  character,  or  of  such  a  nature  as  to  injure  the  texture 
of  the  integument  or  its  nerves,  it  then  produces  a  sensation  o^  pain. 
It  is  essential  to  notice,  however,  that  the  sensation  of  pain  is  not 
a  mere  exaggeration  of  ordinary  sensitive  impressions,  but  is  one 
of  quite  a  different  character,  which  is  superadded  to  the  others,  or 
takes  their  place  altogether.  Just  in  proportion  as  the  contact  of  a 
foreign  body  becomes  painful,  our  ordinary  perceptions  of  its  phy- 
sical properties  are  blunted,  and  the  sense  of  suffering  predominates 
over  ordinary  sensibility.  Thus  if  the  integument  be  gently  touched 
with  the  blade  of  a  knife  we  easily  feel  that  it  is  hard,  cold,  and 
smooth ;  but  if  an  incision  be  made  with  it  in  the  skin,  we  lose  all 
distinct  perception  of  these  qualities,  and  feel  only  the  suffering 
produced  by  the  incision.  We  perceive,  also,  the  difference  in 
temperature  between  cold  and  warm  substances  brought  in  contact 
with  the  skin,  so  long  as  this  difference  is  moderate  in  degree ;  but 
if  a  foreign  body  be  excessively  cold  or  excessively  hot,  we  can 
no  longer  appreciate  its  temperature  by  the  touch,  but  only  its 
injurious  and  destructive  effect.  Thus  the  sensation  caused  by 
touching  frozen  carbonic  acid  is  the  same  with  that  produced  by  a 
red-hot  metal.  Both  substances  blister  the  surface,  but  their  actual 
temperatures  cannot  be  distinguished. 

It  is,  therefore,  a  very  important  fact  in  this  connection,  that  the 
sensibility  to  pain  is  distinct  from  the  po  wer  of  ordinary  sensation.  This 
distinction  was  first  fully  established  by  M.  Beau,  of  Paris,  who  has 
shown  conclusively  that  the  sensibility  to  pain  may  be  diminished 
or  suspended,  while  ordinary  sensation  remains.  This  is  often  seen 
in  patients  who  are  partially  under  the  influence  of  ether  or  chlo- 
roform. The  etherization  may  be  carried  to  such  an  extent  that 
the  patient  may  be  quite  insensible  to  the  pain  of  a  surgical  opera- 
tion, and  yet  remain  perfectly  conscious,  and  even  capable  of  feeling 
the  incisions,  ligatures,  &c.,  though  he  does  not  suffer  from  them. 
It  not  unfrequently  happens,  also,  when  opium  has  been  adminis- 


400  THE    SPINAL    CORD. 

tered  for  the  relief  of  neuralgia,  that  the  pain  is  completely  abolished 
by  the  influence  of  the  drug,  while  the  patient  retains  completely 
his  consciousness  and  his  ordinary  sensibility. 

In  all  cases,  however,  if  the  influence  of  the  narcotic  be  pushed 
to  its  extreme,  both  kinds  of  sensibility  are  suspended  together,  and 
the  patient  becomes  entirely  unconscious  of  external  impressions. 

Motion, — Wherever  muscular  tissue  exists,  in  any  part  of  the 
body,  we  find  the  power  of  motion,  owing  to  the  contractility  of 
the  muscular  fibres.  But  this  power  of  motion,  as  we  have  already 
seen,  is  dependent  on  the  nervous  system.  The  excitement  which 
causes  the  contraction  of  the  muscles  is  transmitted  to  them  by  the 
nervous  filaments  ;  and  if  the  nerve  supplying  a  muscle  or  a  limb 
be  divided  or  seriously  injured,  these  parts  are  at  once  paralyzed 
and  become  incapable  of  voluntary  movement.  A  nerve  which, 
when  irritated,  acts  directly  upon  a  muscle,  producing  contraction, 
is  said  to  be  excitable;  and  its  excitability,  acting  through  the  mus- 
cle, produces  motion  in  the  part  to  which  it  is  distributed. 

The  excitability  of  various  nerves,  however,  often  acts  -during 
life  upon  other  organs,  beside  the  muscles ;  and  the  ultimate  effect 
varies,  of  course,  with  the  properties  of  the  organ  which  is  acted 
upon.  Thus,  the  nervous  excitement  transmitted  to  a  muscle  pro- 
duces contraction,  while  that  transmitted  to  a  gland  produces  an 
increased  secretion,  and  that  conveyed  to  a  vascular  surface  causes 
congestion.  In  all  such  instances,  the  effect  is  produced  by  an 
influence  transmitted  by  the  nerve  directly  to  the  organ  which  is 
called  into  activity. 

But  in  all  the  external  parts  of  the  body  muscular  contraction 
is  the  most  marked  and  palpable  effect  produced  by  the  direct 
iutiuence  of  nervous  excitement.  We  find,  therefore,  that  so  far 
as  we  have  yet  examined  it,  the  nervous  action  shows  itself  princi- 
pally in  two  distinct  and  definite  forms ;  first,  as  sensibility,  or  the 
power  of  sensation,  and  second,  as  excitability  or  the  power  of  pro- 
ducing motion. 

Distinct  Seat  of  Sensation  and  Motion  in  the  Nervous 
System. — Sensation  and  motion  are  usually  the  first  functions 
which  suffer  by  any  injury  inflicted  on  the  nervous  system.  As  a 
general  rule,  they  are  both  suspended  or  impaired  at  the  same  time> 
and  in  a  nearly  equal  degree.  In  a  fainting  fit,  an  attack  of  apo- 
plexy, concussion  or  compression  of  the  brain  or  spinal  cord,  or  a 


DISTINCT    SEAT    OF    SENSATION    AND    MOTION.  401 

•wound  of  any  kind  involving  the  nerves  or  nervous  centres,  insen- 
sibility and  loss  of  motion  usually  appear  simultaneously.  It  is 
difficult,  therefore,  under  ordinary  conditions,  to  trace  out  the 
separate  action  of  these  two  functions,  or  to  ascertain  the  precise 
situation  occupied  by  each. 

This  difficulty,  however,  may  be  removed  by  examining  sepa- 
rately different  parts  of  the  nervous  system.  In  the  instances 
mentioned  above,  the  injury  which  is  inflicted  is  comparatively  an 
extensive  one,  and  involves  at  the  same  time  many  adjacent  parts. 
But  instances  sometimes  occur  in  which  the  two  functions,  sensa- 
tion and  motion,  are  affected  independently  of  each  other,  owing  to 
the  peculiar  character  and  situation  of  the  injury  inflicted.  Sensa- 
tion may  be  impaired  without  loss  of  motion,  and  loss  of  motion 
may  occur  without  injury  to  sensation.  In  tic  douloureux,  for 
example,  we  have  an  exceedingly  painful  affection  of  the  sensitive 
parts  of  the  face,  without  any  impairment  of  its  power  of  motion-, 
and  in  facial  paralysis  we  often  see  a  complete  loss  of  motion  affect- 
ing one  side  of  the  face,  while  the  sensibility  of  the  part  remains 
altogether  unimpaired. 

The  above  facts  first  gave  rise  to  the  belief  that  sensation  and 
motion  might  occupy  distinct  parts  of  the  nervous  system;  since  it 
would  otherwise  be  difficult  to  understand  how  the  two  could  be 
affected  independently  of  each  other  by  anatomical  lesions.  It  has 
accordingly  been  fully  established  by  the  labors  of  Sir  Charles  Bell, 
Miiller,  Panizza,  and  Longet,  that  the  two  functions  do  in  reality 
occupy  distinct  parts  of  the  nervous  system. 

If  any  one  of  the  spinal  nerves,  in  the  living  animal,  after  being 
exposed  at  any  part  of  its  course  outside  the  spinal  canal,  be  divided, 
ligatured,  bruised,  or  otherwise  seriously  injured,  paralysis  of  motion 
and  loss  of  sensation  lare  immediately  produced  in  that  part  of  the 
body  to  which  the  nerve  is  distributed.  If,  on  the  other  hand,  the 
same  nerve  be  pricked,  galvanized,  or  otherwise  gently  irritated,  a 
painful  sensation  and  convulsive  movements  are  produced  in  the 
same  parts.  The  nerve  is  therefore  said  to  be  both  sensitive  and 
excitable ;  sensitive,  because  irritation  of  its  fibres  produces  a  pain- 
ful sensation,  and  excitable,  because  the  same  irritation  causes  mus- 
cular contraction  in  the  parts  below. 

The  result  of  the  experiment,  however,  will  be  different  if  it  be 

tried  upon  the  parts  situated  inside  the  spinal  canal,  and  particularly 

upon  the  anterior  and  posterior  roots  of  the  spinal  nerves.     If  an 

irritation  be  applied,  for  example,  to  the  anterior  root  of  a  spinal 

26 


402  •  THE    SPINAL    CORD. 

nerve,  in  the  living  aninna],  convulsive  movements  are  produced  in 
the  parts  below,  but  there  is  no  painful  sensation.  The  anterior 
root  accordingly  is  said  to  be  excitable,  but  not  sensitive.  If  the 
posterior  root,  on  the  other  hand,  be  irritated,  acute  pain  is  pro- 
duced, but  no  convulsive  movements.  The  posterior  root  is  there- 
fore sensitive,  but  not  excitable.  A  similar  result  is  obtained  by  a 
complete  division  of  the  two  roots.  Division  of  the  anterior  root 
produces  paralysis  of  motion,  but  no  insensibility ;  division  of  the 
posterior  root  produces  complete  loss  of  sensibility,  but  no  muscular 
paralysis. 

We  have  here,  then,  a  separate  localization  of  sensation  and 
motion  in  the  nervous  system ;  and  it  is  accordingly  easy  to  under- 
stand how  one  may  be  impaired  without  injury  to  the  other,  or 
how  both  may  be  simultaneously  affected,  according  to  the  situation 
and  extent  of  the  anatomical  lesion. 

The  two  roots  of  a  spinal  nerve  differ  from  each  other,  further- 
more, in  their  mode  of  transmitting  the  nervous  impulse.  If  the 
posterior  root  be  divided  (Fig.  135)  at  a  b,  and  an  irritation  applied 

Fig,  135. 


Diairram  of  Spinal  Cord  and    Neeves.      The  posterior  root  is  seen  divided  at  n,  h,  the 
anteiiur  at  c,  d. 

to  the  separated  extremity  (a),  no  effect  will  be  produced ;  but  if 
the  irritation  be  applied  to  the  attached  extremity  (h),  a  painful 
sensation  is  immediately  the  result.  The  nervous  force,  therefore, 
travels  in  the  posterior  root  from  without  inward,  but  cannot  pass 
from  within  outward.  If  the  anterior  root,  on  the  other  hand,  be 
divided  at  c,  d,  and  its  attached  extremity  {d)  irritated,  no  effect 


SENSIBILITY    AND    EXCITABILITY    IN    SPINAL    CORD.      403 

follows ;  but  if  the  separated  extremity  (c)  be  irritated,  convulsive 
movements  instantly  take  place.  The  nervous  force,  consequently, 
travels  in  the  anterior  root  from  within  outward,  but  cannot  pass 
from  without  inward. 

The  same  thing  is  true  with  regard  to  the  transmission  of  sensa- 
tion and  motion  in  the  spinal  nerves  outside  the  spinal  canal.  If 
one  of  these  nerves  be  divided  in  the  living  animal,  and  its  attached 
extremity  irritated,  pain  is  produced,  but  no  convulsive  motion ;  if 
the  irritation  be  applied  to  its  separated  extremity,  muscular  con- 
tractions follow,  but  no  painful  sensation. 

There  are,  therefore,  two  kinds  of  filaments  in  the  spinal  nerves, 
not  distinguishable  by  the  eye,  but  entirely  distinct  in  their  charac- 
ter and  function,  viz.,  the  "sensitive"  filaments,  or  those  which 
convey  sensation,  and  the  "  motor"  filaments,  or  those  which  excite 
movement.  These  filaments  "are  never  confounded  with  each  other 
in  their  action,  nor  can  they  perform  each  other's  functions.  The 
sensitive  filaments  convey  the  nervous  force  only  in  a  centripetal, 
the  motor  only  in  a  centrifugal  direction.  The  former  preside  over 
sensation,  and  have  nothing  to  do  with  motion ;  the  latter  preside 
over  motion,  and  have  nothing  to  do  with  sensation.  Within  the 
spinal  canal  the  two  kinds  of  filaments  are  separated  from  each 
other,  constituting  the  anterior  and  posterior  roots  of  each  spinal 
nerve;  but  externally  they  are  mingled  together  in  a  common 
trunk.  While  the  anterior  and  posterior  roots,  therefore,  are  ex- 
clusively sensitive  or  exclusively  motor,  the  spinal  nerves  beyond 
the  junction  of  the  roots  are  called  mixed  nerves,  because  they  con- 
tain at  the  same  time  motor  and  sensitive  filaments.  The  mixed 
nerves  accordingly  preside  at  the  same  time  over  the  functions  of 
movement  and  sensation. 

Distinct  Seat  of  Sensibility  and  Excitability  in  the 
Spinal  Cord. — Various  experimenters  have  demonstrated  the  fact 
that  different  parts  of  the  spinal  cord,  like  the  two  roots  of  the 
spinal  nerves,  are  separately  endowed  with  sensibility  and  excita- 
bility. The  anterior  columns  of  the  cord,  like  the  anterior  roots  of 
the  spinal  nerves,  are  excitable  but  not  sensitive;  the  posterior 
columns,  like  the  posterior  roots  of  the  spinal  nerves,  are  sensitive 
but  not  excitable.  Accordingly,  when  the  spinal  canal  is  opened 
in  the  living  animal,  an  irritation  applied  to  the  anterior  columns 
of  the  cord  produces  immediately  convulsions  in  the  limbs  below ; 
but  there  is  no  indication  of  pain.     On  the  other  hand,  signs  of 


404  THE    SPINAL    CORD. 

acute  pain  become  manifest  whenever  tlie  irritation  is  applied  to 
the  posterior  columns ;  but  no  muscular  contractions  follow,  other 
than  those  of  a  voluntary  character.  Longet  has  found'  that  if  the 
spinal  cord  be  exposed  in  the  lumbar  region  and  completely  divided 
at  that  part  by  transverse  section,  the  application  of  any  irritant  to 
the  anterior  surface  of  the  separated  portion  produces  at  once  con- 
vulsions below ;  while  if  applied  to  the  posterior  columns  behind 
the  point  of  division,  it  has  no  sensible  efi'ect  whatever.  The  an- 
terior and  posterior  columns  of  the  cord  are  accordingly,  so  far, 
analogous  in  their  properties  to  the  anterior  and  posterior  roots  of 
the  spinal  nerves,  and  are  plainly  composed,  to  a  greater  or  less  ex- 
tent, of  a  continuation  of  their  filaments. 

These  filaments,  derived  from  the  anterior  and  posterior  roots  of 
the  spinal  nerves,  pass  upward  through  the  spinal  cord  toward  the 
brain.  An  irritation  applied  to  any  part  of  the  integument  is  then 
conveyed,  along  the  sensitive  filaments  of  the  nerve  and  its  pos- 
terior root,  to  the  spinal  cord;  then  upward,  along  the  longitudinal 
fibres  of  the  cord  to  the  brain,  where  it  produces  a  sensation  corres- 
ponding in  character  with  the  original  irritation.  A  motor  im- 
pulse, on  the  other  hand,  originating  in  the  brain,  is  transmitted 
downward,  along  the  longitudinal  fibres  of  the  cord,  passes  outward 
by  the  anterior  root  of  the  spinal  nerve,  and,  following  the  motor 
filaments  of  the  nerve  through  its  trunk  and  branches,  produces  at 
last  a  muscular  contraction  at  the  point  of  its  final  distribution. 

Crossed  Action  of  the  Spinal  Cord. — As  the  anterior  columns 
of  the  cord  pass  upward  to  join  the  medulla  oblongata,  a  decussa- 
tion takes  place  between  them,  as  we  have  already  mentioned  in 
Chapter  I.  The  fibres  of  the  right  anterior  column  pass  over  to 
the  left  side  of  the  medulla  oblongata,  and  so  upward  to  the  left  side 
of  the  brain ;  while  the  fibres  of  the  left  anterior  column  pass  over 
to  the  right  side  of  the  medulla  oblongata,  and  so  upward  to  the 
right  side  of  the  brain.  This  decussation  may  be  readily  shown 
(as  in  Fig.  130)  by  gently  separating  the  anterior  columns  from  each 
other,  at  the  lower  extremity  of  the  medulla  oblongata,  where  the 
decussating  bundles  may  be  seen  crossing  obliquely  from  side  to 
side,  at  the  bottom  of  the  anterior  median  fissure.  Below  this 
point,  the  anterior  columns  remain  distinct  from  each  other  on  each 
side,  and  do  not  communicate  by  any  further  decussation. 

'  Traite  de  Physiologie,  vol.  ii.  part  2,  p.  8. 


CROSSED    ACTION    OF    THE    SPINAL    CORD.  405 

If  the  anterior  columns  of  the  spinal  cord,  therefore,  be  wounded 
at  any  point  in  the  cervical,  dorsal,  or  lumbar  region,  a  paralysis 
of  voluntary  motion  is  produced  in  the  limbs  below,  on  the  same 
side  with  the  injury.  But  if  a  similar  lesion  occur  in  the  brain,  the 
paralysis  which  results  is  on  the  opposite  side  of  the  body.  Thus 
it  has  long  been  known  that  an  abscess  or  an  apoplectic  hemorrhage 
on  the  right  side  of  the  brain  will  produce  paralysis  of  the  left  side 
of  the  body;  and  injury  of  the  left  side  of  the  brain  will  be  fol- 
lowed by  paralysis  of  the  right  side  of  the  body. 

The  spinal  cord  has  also  a  crossed  action  in  transmitting  sensi- 
tive as  well  as  motor  impulses.  It  has  been  recently  demonstrated 
by  Dr.  Brown-S^quard,'  that  the  crossing  of  the  sensitive  fibres  in 
the  spinal  cord  does  not  take  place,  like  that  of  the  motor  fibres, 
at  its  upper  portion  only,  but  throughout  its  entire  length ;  so  that 
the  sensitive  fibres  of  the  right  spinal  nerves,  very  soon  after  their 
entrance  into  the  cord,  pass  over  to  the  left  side,  and  those  of  the 
left  spinal  nerves  pass  over  to  the  right  side.  For  if  one  lateral 
half  of  the  spinal  cord  of  a  dog  be  divided  in  the  dorsal  region, 
the  power  of  sensation  remains  upon  the  corresponding  side  of  the 
body,  but  is  lost  upon  the  opposite  side.  It  has  been  shown,  fur- 
thermore, by  the  same  observer,^  that  the  sensitive  fibres  of  the 
spinal  nerves  when  they  first  enter  the  cord  join  the  posterior 
columns,  which  are  everywhere  extremely  sensitive  ;  but  that  they 
very  soon  leave  the  posterior  columns,  and,  passing  through  the 
central  parts  of  the  cord,  run  upward  to  the  opposite  side  of  the 
brain.  If  the  posterior  columns,  accordingly,  be  alone  divided  at 
any  part  of  the  spinal  cord,  sensibility  is  not  destroyed  in  all  the 
nerves  behind  the  seat  of  injury,  but  only  in  those  which  enter  the 
cord  at  the  point  of  section ;  since  the  posterior  columns  consist 
of  difierent  nervous  filaments,  joining  them  constantly  on  one  side 
from  below,  and  leaving  them  on  the  other  to  pass  upward  toward 
the  brain. 

The  spinal  cord  has  therefore  a  crossed  action,  both  for  sensation 
and  motion ;  but  the  crossing  of  the  motor  filaments  occurs  only  at 
the  medulla  oblongata,  while  that  of  the  sensitive  filaments  takes 
place  throughout  the  entire  length  of  the  cord. 

'  Experimental  Researches  applied  to  Physiology  and  Pathology.     New  York, 
1853. 

*  Memoirs  sur  la  Physiologie  de  la  Moelle  epini^re  ;  Gazette  Medicale  de  Paris, 
1855. 


406  THE    SPINAL    CORD. 

There  are  certain  important  facts  which  still  remain  to  be  noticed 
regarding  the  mode  of  action  of  the  spinal  cord  and  its  nerves. 
They  are  as  follows  : — 

1.  An  irritation  applied  to  a  spinal  nerve  at  the  middle  of  its  course 
produces  the  same  effect  as  if  it  traversed  its  entire  length.  Thus,  if  the 
sciatic  or  median  nerve  be  irritated  at  any  part  of  its  course,  con- 
traction is  produced  in  the  muscles  to  which  these  nerves  are  dis- 
tributed, just  as  if  the  impulse  had  originated  as  usual  from  the 
brain.  This  fact  depends  upon  the  character  of  the  nervous  fila- 
ments, as  simple  conductors.  Wherever  the  impulse  may  originate, 
the  final  effect  is  manifested  only  at  the  termination  of  the  nerve. 
As  the  impulse  in  the  motor  nerves  travels  always  in  an  outward 
direction,  the  effect  is  always  produced  at  the  muscular  termination 
of  the  filaments,  no  matter  how  small  or  how  large  a  portion  of 
their  length  may  have  been  engaged  in  transmitting  the  stimulus. 

If  the  irritation,  again,  be  applied  to  a  sensitive  nerve  in  the 
middle  of  its  course,  the  painful  sensation  is  felt,  not  at  the  point 
of  the  nerve  directly  irritated,  but  in  that  portion  of  the  integument 
to  which  its  filaments  are  distributed.  Thus,  if  the  ulnar  nerve  be 
accidentally  struck  at  the  point  where  it  lies  behind  the  inner  con- 
dyle of  the  humerus,  a  sensation  of  tingling  and  numbness  is  pro- 
duced in  the  last  two  fingers  of  the  corresponding  hand.  It  is 
common  to  hear  patients  who  have  suffered  amputation  complain  of 
painful  sensations  in  the  amputated  limb  for  weeks  or  months,  and 
sometimes  even  for  years  after  the  operation.  They  assert  that 
they  can  feel  the  separated  parts  as  distinctly  as  if  they  were  still 
attached  to  the  body.  This  sensation,  which  is  a  real  one  and  not 
fictitious,  is  owing  to'  some  irritation  operating  upon  the  divided 
extremities  of  the  nerves  in  the  cicatrized  wound.  Such  an  irrita- 
tion, conveyed  to  the  brain  by  the  sensitive  fibres,  will  produce 
precisely  the  same  sensation  as  if  the  amputated  parts  were  still 
present,  and  the  irritation  actually  applied  to  them. 

It  is  on  this  account  also  that  division  of  the  trifacial  nerve  is 
not  always  effectual  for  the  cure  of  tic  douloureux.  If  the  cause  of 
the  difficulty  be  seated  upon  the  trunk  of  the  nerve,  between  its 
point  of  emergence  from  the  bones  and  its  origin  in  the  brain,  it  is 
evident  that  division  of  the  nerve  upon  the  face  will  be  of  no 
avail ;  since  the  cause  of  irritation  will  still  exist  behind  the  point 
of  section,  and  the  same  painful  sensations  will  still  be  produced  in 
the  brain. 

2.  The  irritability  of  the  motor  filaments  disappears  from  within  out- 


INDEPENDENCE    OF    NERVOUS    FILAMENTS.  407 

ward,  thai  of  the  sensitive  filaraents  from,  without  inward.  Immedi- 
ately after  the  separation  of  the  frog's  leg  from  the  body,  irritation 
of  the  nerve  at  any  point  produces  muscular  contraction  in  the 
limb  below.  As  time  elapses,  however,  and  the  irritability  of  the 
nerve  diminishes,  the  galvanic  current,  in  order  to  produce  con- 
traction, must  be  applied  at  a  point  nearer  its  termination.  Subse- 
quently, the  irritability  of  the  nerve  is  entirely  lost  in  its  upper 
portions,  but  is  retained  in  the  parts  situated  lower  down,  from 
which  also,  in  turn,  it  afterward  disappears ;  receding  in  this  man- 
ner farther  and  farther  toward  the  terminal  distribution  of  the 
nerve,  where  it  finally  disappears  altogether. 

On  the  other  hand,  sensibility  disappears,  at  the  time  of  death, 
first  in  the  extremities.  From  them  the  numbness  gradually  creep.? 
upward,  invading  successively  the  middle  and  upper  portions  of  the 
limbs,  and  the  more  distant  portions  of  the  trunk.  The  central 
parts  are  the  last  to  become  insensible. 

3.  Each  nervous  filament  acts  independently  of  the  rest  throughout  its 
entire  length,  and  does  not  communicate  its  irritation  to  those  which  are 
in  proximity  with  it.  It  is  evident  that  this  is  true  with  regard  to 
the  nerves  of  sensation,  from  the  fact  that  if  the  integument  be 
touched  with  the  point  of  a  needle,  the  sensation  is  referred  to  that 
spot  alone.  Since  the  nervous  filaments  coming  from  it  and  the 
adjacent  parts  are  all  bound  together  in  parallel  bundles,  to  form 
the  trunk  of  the  nerve,  if  any  irritation  were  communicated  from 
one  sensitive  filament  to  another,  the  sensation  produced  would  be 
indefinite  and  diffused,  whereas  it  is  really  confined  to  the  spot  irri- 
tated. If  a  frog's  leg,  furthermore,  be  prepared,  with  the  sciatic 
nerve  attached,  a  few  of  the  fibres  separated  laterally  from  the 
nervous  trunk  for  a  portion  of  its  length,  and  the  poles  of  a  galvanic 
battery  applied  to  the  separated  portion,  the  contractions  which 
follow  in  the  leg  will  not  be  general,  but  will  be  confined  to  those 
muscles  in  which  the  galvanized  nervous  fibres  especially  have 
their  distribution. '  There  are  also  various  instances,  in  the  body, 
of  antagonistic  muscles,  which  must  act  independently  of  each 
other,  but  which  are  supplied  with  nerves  from  a  common  trunk. 
The  superior  and  inferior  straight  muscles  of  the  eyeball,  for 
example,  are  both  supplied  by  the  motor  oculi  communis  nerve. 
Extensor  and  flexor  muscles,  as,  for  example,  those  of  the  fingers, 
are  often  supplied  by  the  same  nerve,  and  yet  act  alternately  with- 
out mutual  interference.     It  is  easy  to  see  that  if  this  were  not  the 


408  THE    SPINAL    CORD. 

case,  confusion  vould  constantly  arise,  both  in  the  perception  of 
sensations,  and  in  the  execution  of  movements. 

4.  There  are  certain  sensations  which  are  excited  simultaneously 
hj  the  same  causes,  and  which  are  termed  associated  sensations  ;  and 
there  are  also  certain  movements  which  take  place  simultaneously, 
and  are  called  associated  movements.  In  the  former  instance,  one  of 
the  associated  sensations  is  called  up  immediately  upon  the  percep- 
tion of  the  other,  without  requiring  any  direct  impulse  of  its  own. 
Thus,  tickling  the  soles  of  the  feet  produces  a  peculiar  sensation 
at  the  epigastrium.  Nausea  is  occasioned  by  certain  disagreeable 
odors,  or  by  rapid  rotation  of  the  body,  so  that  the  landscape  seems 
to  turn  round.  A  striking  example  of  associated  movements,  on 
the  other  hand,  may  be  found  in  the  action  of  the  muscles  of  the 
eyeball.  The  eyeballs  always  accompany  each  other  in  their  lateral 
motions,  turning  to  the  right  or  the  left  side  simultaneously.  It  is 
evident,  however,  that  in  producing  this  correspondence  of  motion, 
the  left  internal  rectus  muscle  must  contract  and  relax  together 
with  the  right  external ;  while  a  similar  harmony  of  action  must 
exist  between  the  right  internal  and  the  left  external.  The  explana- 
tion of  such  singular  correspondences  cannot  be  found  in  the  anato- 
mical arrangement  of  the  muscles  themselves,  nor  in  that  of  the 
nervous  filaments  by  which  they  are  directly  supplied,  but  must  be 
looked  for  in  some  special  endowment  of  the  nervous  centres  from 
which  they  originate. 

Eeflex  Action  of  the  Spinal  Cord. — The  spinal  cord,  as  we 
have  thus  far  examined  it,  may  be  regarded  simply  as  a  great  nerve ; 
that  is,  as  a  bundle  of  motor  and  sensitive  filaments,  connecting 
the  muscles  and  integument  below  with  the  brain  above,  and 
assisting,  in  this  capacity,  in  the  production  of  conscious  sensation 
and  voluntary  motion.  Beside  its  nervous  filaments,  however,  it 
contains  also  a  large  quantity  of  gray  matter,  and  is,  therefore, 
itself  a  ganglionic  centre,  and  capable  of  independent  action  as 
such.  We  shall  now  proceed  to  study  it  in  its  second  capacity,  as 
a  distinct  nervous  centre. 

If  a  frog  be  decapitated,  and  the  body  allowed  to  remain  at  rest 
for  a  few  moments,  so  as  to  recover  from  the  depressing  effects  of 
shock  upon  the  nervous  system,  it  will  be  found  that,  although  sen- 
sation and  consciousness  are  destroyed,  the  power  of  motion  still 
remains.  If  the  skin  of  one  of  the  feet  be  irritated  by  pinching  it 
with  a  pair  of  forceps,  the  leg  is  immediately  drawn  up  toward  the 


REFLEX    ACTION    OF    THE    SPINAL    CORD, 


409 


body,  as  if  to  escape  the  cause  of  irritation.  If  the  irritation  applied 
to  the  foot  be  of  slight  intensity,  the  corresponding  leg  only  will 
move ;  but  if  it  be  more  severe  in  character,  motions  will  often  be 
produced  in  the  posterior  extremity  of  the  opposite  side,  and  even 
in  the  two  fore  legs,  at  the  same  time.  These  motions,  it  is  import- 
ant to  observe,  are  never  spontaneous.  The  decapitated  frog  remains 
perfectly  quiescent  if  left  to  himself.  It  is  only  when  some  cause 
of  irritation  is  applied  externally,  that  movements  occur  as  above 
described. 

It  will  be  seen  that  the  character  of  these  phenomena  indicates 
the  active  operation  of  some  part  of  the  nervous  system,  and  par- 
ticularly of  some  ganglionic  centre.  The  irritation  is  applied  to 
the  skin  of  the  foot,  and  the  muscles  of  the  leg  contract  in  conse- 
quence; showing  evidently  the  intermediate  action  of  a  nervous 
connection  between  the  two. 

The  efi'ect  in  question  is  due  to  the  activity  of  the  spinal  cord, 
operating  as  a  nervous  centre.  In  order  that  the  movements  may 
take  place  as  above,  it  is  essential  that  both  the  integument  and  the 
muscles  should  be  in  communication  with  the  spinal  cord  by  nerv- 
ous filaments,  and  that  the  cord  itself  be  in  a  state  of  integrity.  If 
the  sciatic  nerve  be  divided  in  the  upper  part  of  the  thigh,  irritation 
of  the  skin  below  is  no  longer  followed  by  any  muscular  contrac- 
tion. If  either  the  anterior  or  posterior  roots  of  the  nerve  be 
divided,  the  same  want  of  action  results ;  and  finally,  if,  the  nerve 
and  its  roots  remaining  entire,  the  spinal  cord  itself  be  broken  up 
by  a  needle  introduced  into  the  spinal 
canal,  the  integument  may  then  be 
irritated  or  mutilated  to  any  extent, 
without  exciting  the  least  muscular 
contraction.  It  is  evident,  therefore, 
that  the  spinal  cord  acts,  in  this  case, 
as  a  nervous  centre,  through  which 
the  irritation  applied  to  the  skin  is 
communicated  to  the  muscles.  The 
irritation  first  passes  upward,  as  shown 
in  the  accompanying  diagram  (Fig. 
136),  along  the  sensitive  fibres  of  the 
posterior  root  (a)  to  the  gray  matter 
of  the  cord,  and  is  then  reflected  back, 
along  the  motor  fiV)res  of  the  anterior 
root  (h),  until  it  finally  reaches  the  muscles,  and  produces  a  contrac- 


Fig.  136. 


Diagram  of  Spi  N  AL  Cord  in  V  h  u - 
TIC  A  I.  Skction,  showinj;  refli'x  actioQ. 
— a.  Posterior  root  of  spinal  nerve.  6. 
Anterior  root  of  spinal  nerve. 


410  THE    SPINAL    CORD. 

tion.  This  action  is  known,  accordingly,  as  the  reflex  action  of  the 
spinal  cord. 

It  will  be  remembered  that  this  reflex  action  of  the  cord  is  not 
accompanied    by  volition,  nor  even    by  any  conscious   sensation. 

The  function  of  the  spinal  cord  as  a  nervous  centre  is  simply  to 
convert  an  impression,  received  from  the  skin,  into  a  motor  impulse 
which  is  sent  out  again  to  the  muscles.  There  is  absolutely  no 
farther  action  than  this ;  no  exercise  of  will,  consciousness,  or  judg- 
ment. This  action  will  therefore  take  place  perfectly  well  after 
the  brain  has  been  removed,  and  after  the  entire  sympathetic  sys- 
tem has  also  been  taken  away,  provided  only  that  the  spinal  cord 
and  its  nerves  remain  in  a  state  of  integrity. 

The  existence  of  this  reflex  action  after  death  is  accordingly  an 
evidence  of  the  continued  activity  of  the  spinal  cord,  just  as  con- 
tractility is  an  evidence  of  the  activity  of  the  muscles,  and  irrita- 
bility of  that  of  the  nerves.  Like  the  two  last-mentioned  properties, 
also,  it  continues  for  a  longer  time  after  death  in  cold-blooded  than 
in  warm-blooded  animals.  It  is  for  this  reason  that  frogs  and  other 
reptiles  are  the  most  useful  subjects  for  the  study  of  these  pheno- 
mena, as  for  that  of  most  others  belonging  to  the  nervous  system. 

The  irritability  of  the  spinal  cord,  as  manifested  by  its  reflex 
action,  may  be  very  much  exaggerated  by  certain  diseases,  and  by 
the  operation  of  poisonous  substances.  Tetanus  and  poisoning  by 
strychnine  both  act  in  this  way,  by  heightening  the  irritability  of 
the  spinal  cord,  and  causing  it  to  produce  convulsive  movements 
on  the  application  of  external  stimulus.  It  has  been  observed  that 
the  convulsions  in  tetanus  are  rarely,  if  ever,  spontaneous,  but  that 
they  always  require  to  be  excited  by  some  external  cause,  such  as 
the  accidental  movement  of  the  bedclothes,  the  shutting  of  a  door, 
or  the  sudden  passage  of  a  current  of  air.  Such  slight  causes  of 
irritation,  which  would  be  entirely  inadequate  to  excite  involuntary 
movements  in  the  healthy  condition,  act  upon  the  spinal  cord,  when 
its  irritability  is  heightened  by  disease,  in  such  a  manner  as  to  pro- 
duce violent  convulsions. 

Similar  appearances  are  to  be  seen  in  animals  poisoned  by  strych- 
nine. This  substance  acts  upon  the  spinal  cord  and  increases  its 
irritability,  without  materially  affecting  the  functions  of  the  brain. 
Its  effects  will  show  themselves,  consequently,  without  essential 
modification,  after  the  head  has  been  removed.  If  a  decapitated 
frog  be  poisoned  with  a  moderate  dose  of  strychnine,  the  body  and 
limbs  will  remain  quiescent  so  long  as  there  is  no  external  source 


EEFLEX    ACTION    OF    THE    SPINAL    CORD.  411 

of  excitement ;  but  the  limbs  are  at  once  thrown  into  convulsions 
bj  the  slightest  irritation  applied  to  the  skin,  as,  for  example,  the 
contact  of  a  hair  or  a  feather,  or  even  the  jarring  of  the  table  on 
which  the  animal  is  placed.  That  the  convulsions  in  cases  of 
poisoning  bj  strychnine  are  always  of  a  reflex  character,  and  never 
spontaneous,  is  shown  by  the  following  fact  first  noticed  by  Ber- 
nard,' viz.,  that  if  a  frog  be  poisoned  after  division  of  the  posterior 
roots  of  all  the  spinal  nerves,  while  the  anterior  roots  are  left  un- 
touched, death  takes  place  as  usual,  but  is  not  preceded  by  any  con- 
vulsions. In  this  instance  the  convulsions  are  absent  simply 
because,  owing  to  the  division  of  the  posterior  roots,  external  irri- 
tations cannot  be  communicated  to  the  cord. 

The  reflex  action,  above  described,  may  be  seen  very  distinctly 
in  the  human  subject,  in  certain  cases  of  disease  of  the  spinal  cord. 
If  the  upper  portion  of  the  cord  be  disintegrated  by  inflammatory 
softening,  so  that  its  middle  and  lower  portions  lose  their  natural 
connection  with  the  brain,  paralysis  of  voluntary  motion  and  loss  of 
sensation  ensue  in  all  parts  of  the  body  below  the  seat  of  the  ana- 
tomical lesion.  Under  these  conditions,  the  patient  is  incapable  of 
making  any  muscular  exertion  in  the  paralyzed  parts,  and  is  uncon- 
scious of  any  injury  done  to  the  integument  in  the  same  region. 
Notwithstanding  this,  if  the  soles  of  the  feet  be  gently  irritated 
with  a  feather,  or  with  the  point  of  a  needle,  a  convulsive  twitch- 
ing of  the  toes  will  often  take  place,  and  even  retractile  movements 
of  the  leg  and  thigh,  altogether  without  the  patient's  knowledge. 
Such  movements  may  frequently  be  excited  by  simply  allowing 
the  cool  air  to  come  suddenly  in  contact  with  the  lower  extremities. 
We  have  repeatedly  witnessed  these  phenomena,  in  a  case  of  dis- 
ease of  the  spinal  cord,  where  the  paralysis  and  insensibility  of  the 
lower  extremities  were  complete.  Many  other  similar  instances 
are  reported  by  various  authors. 

The  existence  of  this  reflex  action  of  the  cord  has  enabled  the 
physiologist  to  ascertain  several  other  important  facts  concerning 
the  mode  of  operation  of  the  nervous  system.  M.  Bernard  has 
demonstrated,*  by  a  series  of  extremely  ingenious  experiments  on 
the  action  of  poisonous  substances,  1st,  that  the  irritability  of  the 
muscles  may  be  destroyed,  while  that  of  the  nerves  remains  unal- 

'  Letjons  sttrles  effets  des  Substances  toxiquos  et  medicamenteusps,  Paris,  1857, 
p.  357. 

2  Il.id.,  Chaps.  23  and  24. 


412 


THE    SPINAL    CORD. 


tered ;  and  2d,  that  the  motor  and  sensitive  nervous  filaments  may 
be  paralyzed  independently  of  each  other.  The  above  facts  are 
shown  by  the  three  following  experiments : — 

1.  In  a  living  frog  (Fig.  137),  the  sciatic  nerve  (N)  is  exposed  in 
the  back  part  of  the  thigh,  after  which  a  ligature  is  passed  under- 
neath it  and  drawn  tight  around  the  bone  and  the  remaining  soft 
parts.  In  this  way  the  circulation  is  entirely  cut  off  from  the  limb 
{d),  which  remains  in  connection  with  the  trunk  only  by  means  of 
the  sciatic  nerve.     A  solution  of  sulphocyanide  of  potassium  is  then 

introduced  beneath   the   skin 
^'S-  ^^^-  of  the  back,  at  I,  in  sufficient 

quantity  to  produce  its  speci- 
fic effect.  The  poison  is  then 
absorbed,  and  is  carried  by 
the  circulation  throughout  the 
trunk  and  the  three  extremi- 
ties a,  b,  c ;  while  it  is  pre- 
vented from  entering  the  limb 
d,  by  the  ligature  which  has 
been  placed  about  the  thigh. 
Sulphocyanide  of  potassium 
produces  paralysis,  as  we  have 
previously  mentioned,  by  act- 
ing directly  upon  the  muscu- 
lar tissue.  Accordingly,  a  gal- 
vanic discharge  passed  through 
the  limbs  a,  b,  and  c,  produces 
no  contraction  in  them,  while 
the  same  stimulus,  applied  to 
d,  is  followed  by  a  strong  and 
healthy  reaction.  But  at  the 
moment  when  the  irritation 
is  applied  to  the  poisoned 
limbs  a,  b,  and  c,  though  no 
visible  effect  is  produced  in 
them,  an  active  movement 
takes  place  in  the  healthy 
limb,  d.  This  can  only  be 
owing  to  a  reflex  action  of  the  spinal  cord,  originating  in  the  inte- 
gument of  a,  b,  and  c,  and  transmitted,  by  sensitive  and  motor  fila- 
ments, through  the  cord  to  d.      While  the  muscles  of  the  poisoned 


REFLEX    ACTION    OF   THE    SPINAL    CORD.  413 

Jirribs,  therefore,  have  been  directly  paralyzed,  the  nerves  of  tJte  same 
parts  have  retained  their  irritability. 

2.  If  a  frog  be  poisoned  with  woorara  by  simply  placing  the 
poison  under  the  skin,  no  reflex  action  of  the  spinal  cord  can  be 
demonstrated  after  death.  We  have  already  shown,  from  experi- 
ments detailed  in  Chapter  II.,  that  this  substance  destroys  the  irrita- 
bility of  the  motor  nerves,  without  affecting  that  of  the  muscles.  In 
the  above  instance,  therefore,  where  the  reflex  action  is  abolished,  its 
loss  may  be  owing  to  a  paralysis  of  both  motor  and  sensitive  fila- 
ments, or  to  that  of  the  motor  filaments  alone.  The  following  experi- 
ment, however,  shows  that  the  motor  filaments  are  the  only  ones 
affected.  If  a  frog  be  prepared  as  in  Fig.  137,  and  poisoned  by  the 
introduction  of  woorara  at  /,  when  the  limb  d  is  irritated  its  own 
muscles  react,  while  no  movement  takes,  place  in  a,  b,  or  c;  but  if 
the  irritation  be  applied  to  a,  b,  or  c,  reflex  movements  are  imme- 
diately produced  in  d.  In  the  poisoned  limbs,  therefore,  while  the 
motor  nerves  have  been  paralyzed,  the  sensitive  filaments  have  retained 
their  irritability. 

3.  If  a  frog  be  poisoned  with  strychnine,  introduced  underneath 
the  skin  in  sufficient  quantity,  death  takes  place  after  general  con- 
vulsions, which  are  due,  as  we  have  seen  above,  to  an  unnatural 
excitability  of  the  reflex  action.  This  is  followed,  however,  by  a 
paralysis  of  sensibility,  so  that  after  death  no  reflex  movements 
can  be  produced  by  irritating  the  skin  or  even  the  posterior  roots 
of  the  spinal  nerves.  But  if  the  anterior  roots,  or  the  motor  nerves 
themselves  be  galvanized,  contractions  immediately  take  place  in 
the  corresponding  muscles.  In  this  case,  therefore,  the  sensitive  fila- 
ments have  been  paralyzed,  while  the  motor  filaments  and  the  muscles 
have  retained  their  irritability. 

We  now  come  to  investigate  the  reflex  action  of  the  spinal  cord, 
as  it  takes  place  in  a  healthy  condition  during  life.  This  action 
readily  escapes  notice,  unless  our  attention  be  particularly  directed 
to  it,  because  the  sensations  which  we  are  constantly  receiving,  and 
the  many  voluntary  movements  which  are  continually  executed, 
serve  naturally  to  mask  those  nervous  phenomena  which  take  place 
without  our  immediate  knowledge,  and  over  which  we  exert  no 
voluntary  control.  Such  phenomena,  however,  do  constantly  take 
place,  and  are  of  extreme  physiological  importance.  If  the  surface 
of  the  skin,  for  example,  be  at  any  time  unexpectedly  brought  in 
contact  with  a  heated  body,  the  injured  part  is  often  withdrawn  by 
a  rapid  and  convulsive  movement,  long  before  we  feel  the  pain,  or 


41-i  THE    SPINAL    COED. 

even  fairly  understand  the  cause  of  the  involuntary  act.  If  the 
body  by  any  accident  suddenly  and  unexpectedly  loses  its  balance, 
the  limbs  are  thrown  into  a  position  calculated  to  protect  the  ex- 
posed parts,  and  to  break  the  fall,  by  a  similar  involuntary  and  in- 
stantaneous movement.  The  brain  does  not  act  in  these  cases,  for 
there  is  no  intentional  character  in  the  movement,  nor  even  any 
complete  consciousness  of  its  object.  Everything  indicates  that  it 
is  the  immediate  result  of  a  simple  reflex  action  of  the  spinal  cord. 

The  cord  exerts  also  an  important  and  constant  influence  upon 
the  sphincter  muscles.  The  sphincter  ani  is  habitually  in  a  state  of 
contraction,  so  that  the  contents  of  the  intestine  are  not  allowed  to 
escape.  When  any  external  irritation  is  applied  to  the  anus,  or 
whenever  the  feces  present  themselves  internally,  the  sphincter 
contracts  involuntarily,  and  the  discharge  of  the  feces  is  prevented. 
This  habitual  closure  of  the  sphincter  depends  on  the  reflex  action 
of  the  spinal  cord.  It  is  entirely  an  involuntary  act,  and  will  con* 
tinue,  in  the  healthy  condition,  during  profound  sleep,  as  complete 
and  efl&cient  as  in  the  waking  state. 

When  the  rectum,  however,  has  become  filled  by  the  accumula- 
tion of  feces  from  above,  the  nervous  action  changes.  Then  the 
impression  produced  on  the  mucous  membrane  of  the  distended 
rectum,  conveyed  to  the  spinal  cord,  causes  at  the  same  time  re- 
laxation of  the  sphincter  and  contraction  of  the  rectum  itself;  so 
that  a  discharge  of  the  feces  consequently  takes  place. 

Now  all  these  actions  are  to  some  extent  under  the  control  of 
sensation  and  volition.  The  distended  state  of  the  rectum  is  usually 
accompanied  by  a  distinct  sensation,  and  the  resistance  of  the 
sphincter  may  be  voluntarily  prolonged  for  a  certain  period,  just  as 
the  respiratory  movements,  which  are  usually  involuntary,  may  be 
intentionally  hastened  or  retarded,  or  even  temporarily  suspended. 
But  this  voluntary  power  over  the  sphincter  and  the  rectum  is 
limited.  After  a  time  the  involuntary  impulse,  growing  more 
urgent  with  the  increased  distension  of  the  rectum,  becomes  irre- 
sistible ;  and  the  discharge  finally  takes  place  by  the  simple  reflex 
action  of  the  spinal  cord. 

If  the  spinal  cord  be  injured  in  its  middle  or  upper  portions,  the 
sensibility  and  voluntary  action  of  the  sphincter  are  lost,  because  its 
connection  with  the  brain  has  been  destroyed.  The  evacuation 
then  takes  place  at  once,  by  the  ordinary  mechanism,  as  soon  as 
the  rectum  is  filled,  but  without  any  knowledge  on  the  part  of  the 


REFLEX    ACTION    OF    THE    SPINAL    CORD.  415 

patient.  The  discharges  are  then  said  to  be  "  involuntary  and  un- 
conscious." 

If  the  irritability  of  the  cord,  on  the  other  hand,  be  exaggerated 
by  disease,  while  its  connection  with  the  brain  remains  entire,  the 
distension  of  the  rectum  is  announced  by  the  usual  sensation,  but 
the  reflex  impulse  to  evacuation  is  so  urgent  that  it  cannot  be 
controlled  by  the  will,  and  the  patient  is  compelled  to  allow  it  to 
take  place  at  once.  The  discharges  are  then  said  to  be  simply 
"involuntary." 

Finally,  if  the  substance  of  the  spinal  cord  be  extensively  de- 
stroyed by  accident  or  disease,  the  sphincter  is  permanently  relaxed. 
The  feces  are  then  evacuated  almost  continuously,  without  any 
knowledge  or  control  on  the  part  of  the  patient,  as  fast  as  they 
descend  into  the  rectum  from  the  upper  portions  of  the  intestine. 

Injury  of  the  spinal  cord  produces  a  somewhat  different  effect  on 
the  urinary  bladder.  Its  muscular  fibres  are  directly  paralyzed ; 
and  the  organ,  being  partially  protected  by  elastic  fibres,  both  at 
its  own  orifice  and  along  the  urethra,  becomes  gradually  distended 
by  urine  from  the  kidneys.  The  urine  then  overcomes  the  elas- 
ticity of  the  protecting  fibres,  by  simple  force  of  accumulation,  and 
afterward  dribbles  away  as  fast  as  it  is  excreted  by  the  kidneys. 
Paralysis  of  the  bladder,  therefore,  first  causes  a  permanent  disten- 
sion of  the  organ,  which  is  afterward  followed  by  a  continuous, 
passive,  and  incomplete  discharge  of  its  contents. 

Injury  of  the  spinal  cord  produces  also  an  important,  though 
probably  an  indirect  effect  on  nutrition,  secretion,  animal  heat,  &c., 
in  the  paralyzed  parts.  Diseases  of  the  cord  which  result  in  its 
softening  or  disintegration,  are  notoriously  accompanied  by  consti- 
pation, often  of  an  extremely  obstinate  character.  In  complete 
paraplegia,  also,  the  lower  extremities  become  emaciated.  The 
texture  and  consistency  of  the  muscles  are  altered,  and  the  animal 
temperature  is  considerably  reduced.  All  such  disturbances  of 
nutrition,  however,  which  almost  invariably  follow  upon  local  para- 
lysis, are  no  doubt  immediately  owing  to  the  inactive  condition  of 
the  muscles ;  a  condition  which  naturally  induces  debility  of  the 
circulation,  and  consequently  of  all  those  functions  which  are  de- 
pendent upon  it. 

It  is  less  easy  to  explain  the  connection  between  injury  of  the 
spinal  cord  and  inflammation  of  the  urinary  passages.  It  is,  how- 
ever, a  matter  of  common  observation  among  pathologists,  that 
injury  or  disease  of  the  cord,  particularly  in  the  dorsal  and  upper 


416  THE    SPINAL    CORD. 

lumbar  regions,  is  soon  followed  by  catarrhal  inflammation  of  the 
urinary  passages.  This  gives  rise  to  an  abundant  production  of 
altered  mucus,  which  in  its  turn,  by  causing  an  alkaline  fermenta- 
tion of  the  urine  contained  in  the  bladder,  converts  it  into  an  irri- 
tating and  ammoniacal  liquid,  which  reacts  upon  the  mucous  mem- 
brane and  aggravates  the  previous  inflammation. 

We  find,  therefore,  that  the  spinal  cord,  in  its  character  of  a 
nervous  centre,  exerts  a  general  protective  action  over  the  whole 
body,  it  presides  over  the  involuntary  movements  of  the  limbs 
and  trunk ;  it  regulates  the  action  of  the  sphincters,  the  rectum, 
and  the  bladder;  while  at  the  same  time  it  exerts  an  indirect  influ- 
ence on  the  nutritive  changes  in  those  parts  which  it  supplies  with 
nerves. 


THE    BRAIN.  417 


CHAPTER   IV. 

THE   BRAIN. 

By  the  brain,  or  encephalon,  as  it  is  sometimes  called,  we  mean  all 
that  portion  of  the  nervous  system  which  is  situated  within  the 
cavity  of  the  cranium.  It  consists,  as  we  have  already  shown,  of 
a  series  of  different  ganglia,  connected  with  each  other  by  transverse 
and  longitudinal  commissures. 

Since  we  have  found  the  functions  of  sensation  and  motion,  or 
sensibility  and  excitability,  so  distinctly  separated  in  the  spinal 
cord,  we  should  expect  to  find  the  same  distinction  in  the  interior 
of  the  brain.  These  two  properties  have  indeed  been  found  to  be 
distinct  from  each  other,  so  far  as  they  exist  at  all,  in  the  encephalic 
mass ;  but  it  is  a  very  remarkable  fact  that  they  are  both  confined 
to  very  small  portions  of  the  brain,  in  comparison  with  its  entire 
bulk.  According  to  the  investigations  of  Longet,  neither  the 
olfactory  ganglia,  the  corpora  striata,  the  optic  thalami,  the  tuber- 
cula  quadrigemina,  nor  the  white  or  gray  substance  of  the  cerebrum 
or  the  cerebellum,  are  in  the  least  degree  excitable.  Mechanical 
irritation  of  these  parts  does  not  produce  the  slightest  convulsive 
movement  in  the  muscles  below.  The  application  of  caustic  liquids 
and  the  passage  of  galvanic  currents  are  equally  without  effect. 
The  only  portions  of  the  brain  in  which  irritation  is  followed  by 
convulsive  movements  are  the  anterior  surface  of  the  medulla  ob- 
longata, the  tuber  annulare,  and  the  lower  part  of  the  crura  cerebri ; 
that  is,  the  lower  and  central  parts  of  the  brain,  containing  continu- 
ations of  the  anterior  columns  of  the  cord.  On  the  other  hand, 
neither  the  olfactory  ganglia,  the  corpora  striata,  the  tubercula 
quadrigemina,  nor  the  white  or  gray  substance  of  the  cerebrum  or 
cerebellum,  give  rise,  on  being  irritated,  to  any  painful  sensation. 
The  only  sensitive  parts  are  the  posterior  surface  of  the  medulla 
oblongata,  the  restiform  bodies,  the  processus  e  cerebello  ad  testes, 
and  the  upper  part  of  the  crura  cerebri ;  that  is,  those  portions  of 
the  base  of  the  brain  which  contain  prolongations  of  the  posterior 
columns  of  the  cord. 
27 


418  THE    BRAIN. 

The  most  central  portions  of  the  nervous  system,  therefore,  and 
particularly  the  gray  matter,  are  destitute  of  both  excitability  and 
sensibility.  It  is  only  those  portions  which  serve  to  conduct  sen- 
sations and  nervous  impulses  that  can  be  excited  by  mechanical 
irritation ;  not  the  ganglionic  centres  themselves,  which  receive  and 
originate  the  nervous  impressions. 

We  shall  now  study  in  succession  the  different  ganglia  of  which 
the  brain  is  composed. 

Olfactory  Ganglia. — These  ganglia,  which  in  some  of  the 
lower  animals  are  very  large,  corresponding  in  size  with  the  ex- 
tent of  the  olfactory  membrane  and  the  acuteness  of  the  sense  of 
smell,  are  very  small  in  the  human  subject.  They  are  situated  on 
the  cribriform  plate  of  the  ethmoid  bone,  on  each  side  of  the  crista 
galli,  just  beneath  the  anterior  lobes  of  the  cerebrum.  They  send 
their  nerves  through  the  numerous  perforations  which  exist  in  the 
ethmoid  bone  at  this  part,  and  are  connected  with  the  base  of  the 
brain  by  two  longitudinal  commissures.  The  olfactory  ganglia 
with  their  commissures  are  sometimes  spoken  of  as  the  "  olfactory 
nerves."  They  are  not  nerves,  however,  but  ganglia,  since  they  are 
mostly  composed  of  gray  matter ;  and  the  term  "  olfactory  nerves" 
can  be  properly  applied  only  to  the  filaments  which  originate  from 
them,  and  which  are  afterward  spread  out  in  the  substance  of  the 
olfactory  membrane. 

It  has  been  found  difficult  to  determine  the  function  of  these 
ganglia  by  direct  experiment  on  the  lower  animals.  They  may  be 
destroyed  by  means  of  a  strong  needle  introduced  through  the  bones 
of  the  cranium ;  but  the  signs  of  the  presence  or  absence  of  the 
sense  of  smell,  after  such  an  operation,  are  too  indefinite  to  allow  us 
to  draw  from  them  a  decided  conclusion.  The  anatomical  distribu- 
tion of  their  nerves,  however,  and  the  evident  correspondence  which 
exists,  in  different  species  of  animals,  between  their  degree  of  de- 
velopment and  that  of  the  external  olfactory  organs,  leaves  no  doubt 
as  to  their  true  function.  They  are  the  ganglia  of  the  special  sense 
of  smell,  and  are  not  connected,  in  any  appreciable  degree,  with 
ordinary  sensibility,  nor  with  the  production  of  voluntary  move- 
ments. 

Optic  Thalami. — These  bodies  are  not,  as  their  name  would 
imply,  the  ganglia  of  vision.  Longet  has  found  that  the  power  of 
sight  and  the  sensibility  of  the  pupil  both  remain,  in  birds,  after 


CORPORA    STRIATA. —  HEMISPHERES.  419 

tile  optic  thalami  have  been  thorouglilj  disorganized  ;  and  that  arti- 
ficial irritation  of  the  same  ganglia  has  no  effect  in  producing 
either  contraction  or  dilatation  of  the  pupil.  The  optic  thalami, 
however,  according  to  the  same  observer,  have  a  peculiar  crossed 
action  upon  the  voluntary  movements.  If  both  hemispheres  and 
both  optic  thalami  be  removed  in  the  rabbit,  the  animal  is  still 
capable  of  standing  and  of  using  his  limbs  in  progression.  But  if 
the  right  optic  thalamus  alone  be  removed,  the  animal  falls  at  once 
upon  his  left  side ;  and  if  the  left  thalamus  be  destroyed,  a  similar 
debility  is  manifest  on  the  right  side  of  the  body.  In  these  in- 
stances there  is  no  absolute  paralysis  of  the  side  upon  which  the 
animal  falls,  but  rather  a  simple  want  of  balance  between  the  two 
opposite  sides.  The  exact  mechanism  of  this  peculiar  functional 
disturbance  is  not  well  understood ;  and  but  little  light  has  yet 
been  thrown,  either  by  direct  experiment  or  by  the  facts  of  compa- 
rative anatomy,  on  the  real  function  of  the  optic  thalami. 

Corpora  Striata. — The  function  of  these  ganglia  is  equally 
uncertain  with  that  of  the  preceding.  They  are  traversed,  as  we 
have  already  seen,  by  fibres  coming  from  the  anterior  columns  of 
the  cord;  and  they  are  connected,  by  the  continuation  of  these 
fibres,  with  the  gray  substance  of  the  hemispheres.  They  have 
therefore,  in  all  probability,  like  the  optic  thalami,  some  connection 
with  sensation  and  volition ;  but  the  precise  nature  of  this  connec- 
tion is  at  present  altogether  unknown. 

Hemispheres. — The  hemispheres,  or  the  cerebral  ganglia,  con- 
stitute in  the  human  subject  about  nine-tenths  of  the  whole  mass 
of  the  brain.  Throughout  their  whole  extent  they  are  entirely 
destitute,  as  we  have  already  mentioned,  of  both  sensibility  and  ex- 
citability. Both  the  white  and  gray  substance  may  be  wounded, 
burned,  lacerated,  crushed,  or  galvanized  in  the  living  animal,  with- 
out exciting  any  convulsive  movement  or  any  apparent  sensation. 
In  the  human  subject  a  similar  insensibility  has  been  observed 
when  the  substance  of  the  hemispheres  has  been  exposed  by  acci- 
dental violence,  or  in  the  operation  of  trephining. 

Very  severe  mechanical  injuries  may  also  be  inflicted  upon  the 
hemispheres,  even  in  the  human  subject,  without  producing  any 
directly  fatal  result.  One  of  the  most  remarkable  instances  of  this 
fact  is  a  case  reported  by  Prof.  William  Dctmold,  of  New  York,'  in 

'  Am.  Journ.  of  Med.  Sci.,  January,  ISfjO. 


420  THE    BRAIN, 

which  an  abscess  in  the  anterior  lobe  of  the  brain  was  opened  by  an 
incision  passing  through  the  cerebral  substance,  not  only  without 
any  immediate  bad  eflect,  but  with  great  temporary  relief  to  the 
patient.  This  was  the  case  of  a  laborer  who  was  struck  on  the  left 
side  of  the  forehead  by  a  piece  of  falling  timber,  which  produced  a 
compound  fracture  of  the  skull  at  this  part.  One  or  two  pieces  of 
bone  afterward  became  separated  and  were  removed,  and  the  wound 
subsequently  healed.  Nine  weeks  after  the  accident,  however, 
headache  and  drowsiness  came  on ;  and  the  latter  symptom,  becom- 
ing rapidly  aggravated,  soon  terminated  in  complete  stupor.  At 
this  time,  the  existence  of  an  abscess  being  suspected,  the  cicatrix, 
together  with  the  adherent  portion  of  the  dura  mater,  was  dissected 
away,  several  pieces  of  fractured  bone  removed,  and  the  surface  of 
the  brain  exposed.  A  knife  was  then  passed  into  the  cerebral  sub- 
stance, making  a  wound  one  inch  in  length  and  half  an  inch  in 
depth,  when  the  abscess  was  reached  and  over  two  ounces  of  pus 
discharged.  The  patient  immediately  aroused  from  his  comatose 
condition,  so  that  he  was  able  to  speak ;  and  in  a  few  days  reco- 
vered, to  a  very  considerable  extent,  his  cheerfulness,  intelligence, 
and  appetite.  Subsequently,  however,  the  collection  of  pus  re- 
turned, accompanied  by  a  renewal  of  the  previous  symptoms ;  and 
the  patient  finally  died  at  the  end  of  seven  weeks  from  the  time  of 
opening  the  abscess. 

Another  and  still  more  striking  instance  of  recovery  from  severe 
injury  of  the  brain  is  reported  by  Prof.  H.  J.  Bigelow  in  the 
American  Journal  of  Medical  Sciences  for  July,  1850.  In  this  case,  a 
pointed  iron  bar,  three  feet  and  a  half  in  length,  and  one  inch  and  a 
quarter  in  diameter,  was  driven  through  the  patient's  head  by  the 
premature  blasting  of  a  rock.  The  bar  entered  the  left  side  of  the 
face,  just  in  front  of  the  angle  of  the  jaw,  and  passed  obliquely 
upward,  inside  the  zygomatic  arch  and  through  the  anterior  part 
of  the  cranial  cavity,  emerging  from  the  top  of  the  frontal  bone  on 
the  median  line,  just  in  front  of  the  point  of  union  of  the  coronal 
and  sagittal  sutures.  The  patient  was  at  first  stunned,  but  soon 
recovered  himself  so  far  as  to  be  able  to  converse  intelligently,  rode 
home  in  a  common  cart,  and  with  a  little  assistance  walked  up  stairs 
to  his  room.  He  became  delirious  "o'ithin  two  days  after  the  acci- 
dent, and  subsequently  remained  partly  delirious  and  partly  coma- 
tose for  about  three  weeks.  He  then  began  to  improve,  and  at  the 
end  of  rather  more  than  two  months  from  the  date  of  the  injury, 
was  able  to  walk  about.     At  the  end  of  sixteen  months  he  was  in 


HEMISPHERES. 


421 


perfect  health,  with  the  wounds  healed,  and  with  the  mental  and 
bodily  functions  entirely  unimpaired,  except  that  sight  was  perma- 
nently lost  in  the  eye  of  the  injured  side. 

The  hemispheres,  furthermore,  are  not  the  seat  of  sensation  or  of 
volition,  nor  are  they  immediately  essential  to  the  continuance  of 
life.  In  quadrupeds,  the  complete  removal  of  the  hemispheres  is 
attended  with  so  much  hemorrhage  that  the  operation  is  generally 
fatal  from  this  cause  within  a  few  minutes.  In  birds,  however,  it 
may  be  performed  without  any  immediate  danger  to  life,  Longet 
has  removed  the  hemispheres  in  pigeons  and  fowls,  and  has  kept 
these  animals  afterward  for  several  days,  with  most  of  the  organic 
functions  unimpaired.  We  have  frequently  performed  the  same 
experiment  upon  pigeons,  with  a  similar  favorable  result. 

The  effect  of  this  mutilation  is  simply  to  plunge  the  animal  into 
a  state  of  profound  stupor,  in  which  he  is  almost  entirely  inatten- 
tive to  surrounding  objects.  The  bird  remains  sitting  motionless 
upon  his  perch,  or  standing  upon  the  ground,  with  the  eyes  closed, 
and  the  head  sunk  between  the  shoulders.  (Fig.  138.)     The  plu- 

Fig.  138. 


Pigeon,   after   Removal   of    the   Hemispheres. 


mage  is  smooth  and  glossy,  but  is  uniformly  expanded,  by  a  kind 
of  erection  of  the  feathers,  so  that  the  body  appears  somewhat 
puffed  out,  and  larger  than  natural.  Occasionally  the  bird  opens 
his  eyes  with  a  vacant  stare,  stretches  his  neck,  perhaps  shakes  his 
bill  once  or  twice,  or  smooths  down  the  feathers  upon  his  shoulders, 
and  then  relapses  into  his  former  apathetic  condition.  This  state 
of  immobility,  however,  is  not  accompanied  by  the  loss  of  sight,  of 


422  THE    BRAIN. 

hearing,  or  of  ordinary  sensibility.  All  these  functions  remain,  as 
well  as  that  of  voluntary  motion.  If  a  pistol  be  discharged  behind 
the  back  of  the  animal,  he  at  once  opens  his  eyes,  moves  his  head 
half  round,  and  gives  evident  signs  of  having  heard  the  report ;  but 
he  immediately  becomes  quiet  again,  and  pays  no  farther  attention 
to  it.  Sight  is  also  retained,  since  the  bird  will  sometimes  fix  its 
eye  on  a  particular  object,  and  watch  it  for  several  seconds  together. 
Longet  has  even  found  that  by  moving  a  lighted  candle  before  the 
animal's  eyes  in  a  dark  place,  the  head  of  the  bird  will  often  follow 
the  movements  of  the  candle  from  side  to  side  or  in  a  circle,  showing 
that  the  impression  of  light  is  actually  perceived  by  the  sensorium. 
Ordinary  sensation  also  remains,  after  removal  of  the  hemispheres, 
together  with  voluntary  motion.  If  the  foot  be  pinched  with  a 
pair  of  forceps,  the  bird  becomes  partially  aroused,  moves  uneasily 
once  or  twice  from  side  to  side,  and  is  evidently  annoyed  at  the 
irritation. 

The  animal  is  still  capable,  therefore,  after  removal  of  the  hemi- 
spheres, of  receiving  sensations  from  external  objects.  But  these 
sensations  appear  to  make  upon  him  no  lasting  impression.  He  is 
incapable  of  connecting  with  his  perceptions  any  distinct  succession 
of  ideas.  He  hears,  for  example,  the  report  of  a  pistol,  but  he  is  not 
alarmed  by  it ;  for  the  sound,  though  distinctly  enough  perceived, 
does  not  suggest  any  idea  of  danger  or  injury.  There  is  accord- 
ingly no  power  of  forming  mental  associations,  nor  of  perceiving 
the  relation  between  external  objects.  The  memory,  more  particu- 
larly, is  altogether  destroyed,  and  the  recollection  of  sensation  is 
not  retained  from  one  moment  to  another.  The  limbs  and  muscles 
are  still  under  the  control  of  the  will ;  but  the  will  itself  is  inactive, 
because  apparently  it  lacks  its  usual  mental  stimulus  and  direction. 
The  powers  which  have  been  lost,  therefore,  by  destruction  of  the 
cerebral  hemispheres,  are  altogether  of  a  mental  or  intellectual 
character ;  that  is,  the  power  of  comparing  with  each  other  different 
ideas,  and  of  perceiving  the  proper  relation  between  them. 

The  same  result  is  well  known  to  follow,  in  the  human  subject, 
from  injury  or  disease  of  these  parts.  A  disturbance  of  the  mental 
powers  has  long  been  recognized  as  the  ordinary  consequence  of 
lesions  of  the  brain.  In  cases  of  impending  apoplexy,  for  example, 
or  of  softening  of  the  cerebral  substance,  among  the  earliest  and 
most  constant  phenomena  is  a  loss  or  impairment  of  the  memory. 
The  patient  forgets  the  names  of  particular  objects  or  of  particular 
persons ;  or  he  is  unable  to  calculate  numbers  with  his  usual  facility. 


HEMISPHERES.  423 

His  mental  derangement  is  often  shown  in  the  undue  estimate  which 
be  forms  of  passing  events.  He  is  no  longer  able  to  appreciate  the 
true  relation  between  different  objects  and  different  phenomena. 
Thus,  he  will  show  an  exaggerated  degree  of  solicitude  about  a 
trivial  occurrence,  and  will  pay  no  attention  to  other  matters  of 
real  importance.  As  the  difficulty  increases,  he  becomes  careless 
of  the  directions  and  advice  of  his  attendants,  and  must  be  watched 
and  managed  like  a  child  or  an  imbecile.  After  a  certain  period, 
he  no  longer  appreciates  the  lapse  of  time,  and  even  loses  the  dis- 
tinction between  day  and  night.  Finally,  when  the  injury  to  the 
hemispheres  is  complete,  the  senses  may  still  remain  active  and 
impressible,  while  the  patient  is  completely  deprived  of  intelligence, 
memory,  and  judgment. 

If  we  examine  the  comparative  development  of  the  hemispheres 
in  different  species  of  animals,  and  in  different  races  of  men,  we 
shall  find  that  the  size  of  these  ganglia  corresponds  very  closely 
with  the  degree  of  intelligence  possessed  by  the  individual.  We 
have  already  traced,  in  a  preceding  chapter,  the  gradual  increase 
in  size  of  the  hemispheres  in  fish,  reptiles,  .birds,  and  quadrupeds : 
four  classes  of  animals  which  may  be  arranged,  with  regard  to  the 
amount  of  intelligence  possessed  by  each,  in  precisely  the  same 
order  of  succession.  Among  quadrupeds,  the  elephant  has  much 
the  largest  and  most  perfectly  formed  cerebrum,  in  proportion  to 
the  size  of  the  entire  body ;  and  of  all  quadrupeds  he  is  proverbially 
the  most  intelligent  and  the  most  teachable.  It  is  important  to 
observe  in  this  connection,  that  the  kind  of  intelligence  which 
characterizes  the  elephant  and  some  other  of  the  lower  animals, 
and  which  most  nearly  resembles  that  of  man,  is  a  teachahle  intelli- 
gence ;  a  very  different  thing  from  the  intelligence  which  depends 
upon  instinct,  such  as  that  of  insects,  for  example,  or  birds  of  pas- 
sage. Instinct  is  unvarying,  and  always  does  the  same  thing  in  the 
same  manner,  with  endless  repetition ;  but  intelligence  is  a  power 
which  adapts  itself  to  new  circumstances,  and  enables  its  possessor, 
by  comprehending  and  retaining  new  ideas,  to  profit  by  experience. 
It  is  this  quality  which  distinguishes  the  higher  classes  of  animals 
from  the  lower ;  and  which,  in  a  very  much  greater  degree,  con- 
stitutes the  intellectual  superiority  of  man  himself.  The  size  of 
the  cerebrum  in  man  is  accordingly  very  much  greater,  in  propor- 
tion to  that  of  the  entire  body,  than  in  any  of  the  lower  animals ; 
while  other  parts  of  the  brain,  on  the  contrary,  such  as  the  olfactory 
ganglia  or  the  optic  tubercles,  are  frequently  smaller  in  him  than 


424  THE    BKAIN. 

in  thera.  For  while  man  is  superior  in  general  intelligence  to  all 
the  lower  animals,  he  is  inferior  to  many  of  them  in  the  acuteness 
of  the  special  senses. 

As  a  general  rulC;  also,  the  size  of  the  cerebrum  in  different 
races  and  in  different  individuals  corresponds  with  the  grade  of 
their  intelligence.  The  size  of  the  cranium,  as  compared  with  that 
of  the  face,  is  smallest  in  the  savage  negro  and  Indian  tribes  ;  larger 
in  the  civilized  or  semi-civilized  Chinese,  Malay,  Arab,  and  Japan- 
ese ;  while  it  is  largest  of  all  in  the  enlightened  European  races. 
This  difference  in  the  development  of  the  brain  is  not  probably  an 
effect  of  long-continued  civilization  or  otherwise;  but  it  is,  on  the 
contrary,  the  superiority  in  cerebral  development  which  makes 
some  races  readily  susceptible  of  civilization,  while  others  are 
either  altogether  incapable  of  it,  or  can  only  advance  in  it  to  a 
certain  limit.  Although  all  races  therefore  may,  perhaps,  be  said 
to  start  from  the  same  level  of  absolute  ignorance,  yet  after  the 
lapse  of  a  certain  time  one  race  will  have  advanced  farther  in 
civilization  than  another,  owing  to  a  superior  capacity  for  improve- 
ment, dependent  on  original  organization. 

The  same  thing  is  true  with  regard  to  different  individuals.  At 
birth,  all  men  are  equally  ignorant ;  and  yet  at  the  end  of  a  certain 
period  one  will  have  acquired  a  very  much  greater  intellectual 
power  than  another,  even  under  similar  conditions  of  training, 
education,  &c.  He  has  been  able  to  accumulate  more  information 
from  the  same  sources,  and  to  use  the  same  experience  to  better 
advantage  than  his  associates;  and  the  result  of  this  is  a  certain 
intellectual  superiority,  which  becomes  still  greater  by  its  own 
exercise.  This  superiorit}'-,  it  will  be  observed,  lies  not  so  much 
in  the  power  of  perceiving  external  objects  and  events,  and  of  re- 
cognizing the  connection  between  them,  as  in  that  of  drawing  con- 
clusions from  one  fact  to  another,  and  of  adapting  to  new  combina- 
tions the  knowledge  which  has  already  been  acquired. 

It  is  this  particular  kind  of  intellectual  difference,  existing  in  a 
marked  degree,  between  animals,  races,  and  individuals,  which  cor- 
responds with  the  difference  in  development  of  the  cerebral  hemi- 
spheres. "We  have,  therefore,  evidence  from  three  different  sources 
that  the  cerebral  hemispheres  are  the  seat  of  the  reasoning  powers, 
or  of  the  intellectual  faculties  proper.  First,  when  these  ganglia 
are  removed  in  the  lower  animals,  the  intellectual  faculties  are  the 
only  ones  which  are  lost.  Secondly,  injury  to  these  ganglia,  in  the 
human  subject,  is  followed  by  a  corresponding  impairment  of  the 


HEMISPHERES.  425 

same  faculties.  Thirdly,  in  different  species  of  animals,  as  well  as 
in  different  races  of  men  and  in  different  individuals,  the  develop- 
ment of  these  faculties  is  in  proportion  to  that  of  the  cerebral 
hemispheres. 

When  we  say,  however,  that  the  hemispheres  are  the  seat  of  the 
intellectual  faculties,  of  memory,  reason,  judgment,  and  the  like, 
we  do  not  mean  that  these  faculties  are,  strictly  speaking,  located 
in  the  substance  of  the  hemispheres,  or  that  they  belong  directly  to 
the  matter  of  which  the  hemispheres  are  composed.  The  hemi- 
spherical ganglia  are  simply  the  .instruments  through  which  the 
intellectual  powers  manifest  themselves,  and  which  are  accordingly 
necessary  to  their  operation.  If  these  instruments  be  imperfect  in 
structure,  or  be  damaged  in  any  manner  by  violence  or  disease,  the 
manifestations  of  intelligence  are  affected  in  a  corresponding  degree. 
So  far,  therefore,  as  the  mental  faculties  are  the  subject  of  physio- 
logical research  and  experiment,  they  are  necessarily  connected 
with  the  hemispherical  ganglia;  and  the  result  of  investigation 
shows  this  connection  to  be  extremely  intimate  and  important  in 
its  character. 

There  are,  however,  various  circumstances  which  modify,  in 
particular  cases,  the  general  rule  given  above,  viz.,  that  the  larger 
the  cerebrum  the  greater  the  intellectual  superiority.  The  func- 
tional activity  of  the  brain  is  modified,  no  doubt,  by  its  texture  as 
well  as  by  its  size ;  and  an  increased  excitability  may  compensate, 
partially  or  wholly,  for  a  deficiency  in  bulk.  This  fact  is  some- 
times illustrated  in  the  case  of  idiots.  There  are  instances  where 
idiotic  children  with  small  brains  are  less  imbecile  and  helpless 
than  others  with  a  larger  development,  owing  to  a  certain  vivacity 
and  impressibility  of  organization  whi6h  take  the  place,  to  a  certain 
extent,  of  the  purely  intellectual  faculties. 

This  was  the  case,  in  a  marked  degree,  with  a  pair  of  dwarfed 
and  idiotic  Central  American  children,  who  were  exhibited  some 
years  ago  in  various  parts  of  the  United  States,  under  the  name  of 
the  "  Aztec  children."  They  were  a  boy  and  a  girl,  aged  respectively 
about  seven  and  five  years.  The  boy  was  2  feet  9f  inches  high,  and 
weighed  a  little  over  20  pounds.  The  girl  was  2  feet  5 J  inches 
high,  and  weighed  17  pounds.  Their  bodies  were  tolerably  well 
proportioned,  but  the  cranial  cavities,  as  shown  by  the  accompany- 
ing portraits,  were  extremely  small. 

The  antero-posterior  diameter  of  the  boy's  head  was  only  4|- 
inches,  the  transverse  diameter  less  than  4  inches.      The  antero- 


426 


THE    BRAIN. 


posterior  diameter  of  the  girl's  liead  was  4|-  inclies,  the  transverse 
diameter  only  8|  inches.  The  habits  of  these  children,  so  far  as 
regards  feeding  and  taking  care  of  themselves,  were  those  of  chil- 


FiR.  139. 


Aztec  Children.  —  Taken  from  life,  at  five  and  seven  years  of  age. 


dren  two  or  three  years  of  age.  They  were  incapable  of  learning 
to  talk,  and  could  only  repeat  a  few  isolated  words.  Notwithstand- 
ing, however,  the  extremely  limited  range  of  their  intellectual 
powers,  these  children  were  remarkably  vivacious  and  excitable. 
While  awake  they  were  in  almost  constant  motion,  and  any  new 
object  or  toy  presented  to  them  immediately  attracted  their  atten- 
tion, and  evidentl}'  awakened  a  lively  curiosity.  They  were  ac- 
cordingly easily  influenced  by  proper  management,  and  understood 
readily  the  meaning  of  those  who  addressed  them,  so  far  as  this 
meaning  could  be  conveyed  by  gesticulation  and  the  tones  of  the 
voice.  Their  expression  and  general  appearance,  though  decidedly 
idiotic,  were  not  at  all  disagreeable  or  repulsive ;  and  they  were 
much  less  troublesome  to  the  persons  who  had  them  in  charge  than 
is  often  the  case  with  idiots  possessing  a  larger  cerebral  development. 

It  may  also  be  observed  that  the  purely  intellectual  or  reasoning 
powers  are  not  the  only  element  in  the  mental  superiority  of  certain 
races  or  of  particular  individuals  over  their  associates.  There  is 
also  a  certain  rapidity  of  perception  and  strength  of  will  which  may 
sometimes  overbalance  greater  intellectual  acquirements  and  more 
cultivated  reasoning  powers.  These,  however,  are  different  facul- 
ties from  the  latter ;  and  occupy,  as  we  shall  hereafter  see,  different 
parts  of  the  encephalon. 

A  very  remarkable  physiological  doctrine,  dependent  partly  on 
the  foregoing  facts,  was  brought'  forward  some  years  ago  by  Gall 


HEMISPHERES.  427 

and  Spurzheim,  under  the  name  of  Phrenology.  These  observers 
recognized  the  fact  that  the  intellectual  powers  are  undoubtedly 
seated  in  the  brain,  and  that  the  development  of  the  brain  is,  as  a 
general  rule,  in  correspondence  with  the  activity  of  these  powers. 
They  noticed  also  that  in  other  parts  of  the  nervous  system,  different 
functions  occupy  different  situations;  and  regarding  the  mind  as 
made  up  of  many  distinct  mental  faculties,  they  conceived  the  idea 
that  these  different  faculties  might  be  seated  in  different  parts  of 
the  cerebral  mass.  If  so,  each  separate  portion  of  the  brain  would 
undoubtedly  be  more  or  less  developed  in  proportion  to  the  activity 
of  the  mental  trait  or  faculty  residing  in  it.  The  shape  of  the  head 
■would  then  vary  in  different  individuals,  in  accordance  with  their 
mental  peculiarities ;  and  the  character  and  endowments  of  the  in- 
dividual might  therefore  be  estimated  from  an  examination  of  the 
elevations  and  depressions  on  the  surface  of  the  cranium. 

Accordingly,  the  authors  of  this  doctrine  endeavored,  by  examin- 
ing the  heads  of  various  individuals  whose  character  was  already 
known,  to  ascertain  the  location  of  the  different  mental  faculties. 
In  this  manner  they  finally  succeeded,  as  they  supposed,  in  accom- 
plishing their  object ;  after  which  they  prepared  a  chart,  in  which 
the  surface  of  the  cranium  was  mapped  out  into  some  thirty  or  forty 
different  regions,  corresponding  with  as  many  different  mental  traits 
or  faculties.  With  the  assistance  of  this  chart  it  was  thought  that 
phrenology  might  be  practised  as  an  art ;  and  that,  by  one  skilled 
in  its  application,  the  character  of  a  stranger  might  be  discovered 
by  simply  examining  the  external  conformation  of  his  head. 

We  shall  not  expend  much  time  in  discussing  the  claims  of  phre- 
nology to  rank  as  a  science  or  an  art,  since  we  believe  that  it  has 
of  late  years  been  almost  wholly  discarded  by  scientific  men,  owing 
to  the  very  evident  deficiencies  of  the  basis  upon  which  it  was 
founded.  Passing  over,  therefore,  many  minor  details,  we  will 
merely  point  out,  as  matters  of  physiological  interest,  the  principal 
defects  which  must  always  prevent  the  establishment  of  phrenology 
as  a  science,  and  its  application  as  an  art. 

First,  though  we  have  no  reason  for  denying  that  different  parts 
of  the  brain  may  be  occupied  by  different  intellectual  faculties, 
there  is  no  direct  evidence  which  would  show  this  to  be  the  case. 
Phrenologists  include,  in  those  parts  of  the  brain  which  they  em- 
ploy for  examination,  both  the  cerebrum  and  cerebellum ;  and  they 
justly  regard  the  external  parts  of  these  bodies,  viz.,  the  layer  of 
gray  matter  which  occupies  their  surface,  as  the  ganglionic  portion 


428 


THE    BRAIN. 


in  which  must  reside  more  especially  the  nervous  functions  which 
they  possess.  But  this  layer  of  gray  matter,  in  each  principal  por- 
tion of  the  brain,  is  continuous  throughout.  There  is  no  anatomical 
division  or  limit  between  its  different  parts,  like  those  between 
the  different  ganglia  in  other  portions  of  the  nervous  system ;  and 
consequently  such  divisions  of  the  cerebrum  and  cerebellum  must 
be  altogether  arbitrary  in  character,  and  not  dependent  on  any 
anatomical  basis. 

Secondly,  the  only  means  of  ascertaining  the  location  of  the 
different  mental  traits,  supposing  them  to  occupy  different  parts  of 
the  brain,  would  be  that  adopted  by  Gall  and  Spurzheim,  viz.,  to 
make  an  accurate  comparison,  in  a  suf&cient  number  of  cases,  of  the 
form  of  the  head  in  individuals  of  known  character.  But  the  prac- 
tical difficulty  of  accomplishing  this  is  very  great.  It  requires  a 
long  acquaintance  and  close  observation  to  learn  accurately  the 
character  of  a  single  person ;  and  it  is  in  this  kind  of  observation, 
more  than  in  any  other,  that  we  are  proverbially  liable  to  mistakes. 
It  is  extremely  improbable,  therefore,  that  either  Gall  or  Spurzheim 
could,  in  a  single  lifetime,  have  accomplished  this  comparison  in  so 
many  instances  as  to  furnish  a  reliable  basis  for  the  construction  of 
a  phrenological  chart. 

A  still  more  serious  practical  difficulty,  however,  is  the  following. 
The  different  intellectual  faculties  being  supposed  to  reside  in  the 
layer  of  gray  substance  constituting  the  surfaces  of  the  cerebrum 

and  cerebellum,  they  must  of  course  be 
distributed  throughout  this  layer,  where- 
ever  it  exists.  Gall  and  Spurzheim 
located  all  the  mental  faculties  in  those 
parts  of  the  brain  which  are  accessible 
to  external  exploration.  An  examina- 
tion of  different  sections  of  the  brain 
will  show,  however,  that  the  greater  por- 
tion of  the  gray  substance  is  so  placed, 
that  its  quantity  cannot  be  estimated  by 
an  external  examination  through  the 
skull.  The  only  portions  which  are 
exposed  to  such  an  examination  are  the 
upper  and  lateral  portions  of  the  con- 
vexities of  the  hemispheres,  together 
with  the  posterior  edge  and  part  of  the 
under  surface  of  the  cerebellum.   (Fig,  140.)     A  very  extensive 


Fig.  140. 


Diagram  of  the  Brain  in  sittt, 
showing  those  portions  which  ai'e  ex- 
posed to  examination. 


HEMISPHERES. 


429 


Fig.  141. 


portion  of  the  cerebral  surface,  however,  remains  concealed  in  such 
a  manner  that  it  cannot  possibly  be  subjected  to  examination,  viz., 
the  entire  base  of  the  brain,  with  the  under  surface  of  the  ante- 
rior and  middle  lobes  (i,  2);  the  upper  surface  of  the  cerebellum 
(3)  and  the  inferior  surface  of  the  posterior  lobe  of  the  cerebrum 
which  covers  it  (4) ;  that  portion  of  the  cerebellum  situated  above  the 
medulla  oblongata  (5) ;  and  the  two  opposite  convoluted  surfaces  in 
the  fissure  of  Sylvius  (e,  7),  where  the  anterior  and  middle  lobes  of 
the  cerebrum  lie  in  contact  with  each  other.  The  whole  extent, 
also,  of  the  cerebral  surfaces  which  are  opposed  to  each  other  in  the 
great  longitudinal  fissure  (Fig.  141),  throughout  its  entire  length, 
are  equally  protected  by  their  position,  and 
concealed  from  external  examination.  The 
whole  of  the  convoluted  surface  of  the  brain 
must,  however,  be  regarded  as  of  equal  im- 
portance in  the  distribution  of  the  mental 
qualities ;  and  yet  it  is  evident  that  not 
more  than  one-third  or  one-quarter  of  this 
surface  is  so  placed  that  it  can  be  examined 
by  external  manipulation.  It  must  further- 
more be  recollected  that  the  gray  matter  of 
the  cerebrum  and  cerebellum  is  everywhere 
convoluted,  and  that  the  convolutions  pene- 
trate to  various  depths  in  the  substance  of 
the  brain.  Even  if  we  were  able  to  feel,  therefore,  the  external 
surface  of  the  brain  itself,  it  would  not  be  the  entire  convolutions, 
but  only  their  superficial  edges,  that  we  should  really  be  able  to 
examine.  And  yet  the  amount  of  gray  matter  contained  in  a  given 
space  depends  quite  as  much  upon  the  depth  to  which  the  convolu- 
tions penetrate,  as  upon  the  prominence  of  their  edges. 

While  phrenology,  therefore,  is  partially  founded  upon  acknow- 
ledged physiological  facts,  there  are  yet  essential  deficiencies  in  its 
scientific  basis,  as  well  as  insurmountable  difficulties  in  the  way  of 
its  practical  application. 


Transverse  section  of  B  r  a  i  n, 
showing  depth  of  great  longi- 
tudinal fissure,  at  a. 


Cerebellum. — The  cerebellum  is  the  second  ganglion  of  the 
encephalon,  in  respect  to  size.  If  it  be  examined,  moreover,  in 
regard  to  the  form  and  disposition  of  its  convolutions,  it  will  be 
seen  that  these  are  much  more  complicated  and  more  numerous 
than  in  the  cerebrum,  and  penetrate  much  deeper  into  its  substance. 
Though  the  cerebellum  therefore  is  smaller,  as  a  whole,  than  the 


430  THE    BKAIN. 

cerebrum,  it  contains;  in  proportion  to  its  size,  a  much  larger  quan- 
tity of  gray  matter. 

In  examining  the  comparative  development  of  the  brain,  also,  in 
different  classes  and  species  of  animals,  we  find  that  the  cerebellum 
nearly  always  keeps  pace,  in  this  respect,  with  the  cerebrum.  These 
facts  would  lead  us  to  regard  it  as  a  ganglion  hardly  secondary  in 
importance  to  the  cerebrum  itself. 

Physiologists,  however,  have  thus  far  failed  to  demonstrate  the 
nature  of  its  function  with  the  same  degree  of  precision  as  that  of 
many  other  parts  of  the  brain.  The  opinion  of  Gall,  which  located 
in  the  cerebellum  the  sexual  impulse  and  instincts,  is  at  the  present 
day  generally  abandoned;  for  the  reason  that  it  has  not  been  found 
to  be  sufficiently  supported  by  anatomical  and  experimental  facts, 
many  of  which  are  indeed  directly  opposed  to  it.  The  opinion 
which  has  of  late  years  been  received  with  the  most  favor  is  that 
first  advocated  by  Flourens,  which  attributes  to  the  cerebellum  the 
power  of  associating  or  "co-ordinating"  the  different  voluntary 
movements. 

It  is  evident,  indeed,  that  such  a  power  does  actually  reside  in 
some  part  of  the  nervous  system.  No  movements  are  effected  by 
the  independent  contraction  of  single  muscles;  but  always  by 
several  muscles  acting  in  harmony  with  each  other.  The  number 
and  complication  of  these  associated  movements  vary  in  different 
classes  of  animals.  In  fish,  for  example,  progression  is  accom- 
plished in  the  simplest  possible  manner,  viz.,  by  the  lateral  flexion 
and  extension  of  the  vertebral  column.  In  serpents  it  is  much  the 
same.  In  frogs,  lizards,  and  turtles,  on  the  other  hand,  the  four 
jointed  extremities  come  into  play,  and  the  movements  are  some- 
what complicated.  They  are  still  more  so  in  birds  and  quadrupeds ; 
and  finally,  in  the  human  subject  they  become  both  varied  and 
complicated  in  the  highest  degree.  Even  in  maintaining  the  ordi- 
nary postures  of  standing  and  sitting,  there  are  many  different  mus- 
cles acting  together,  in  each  of  which  the  degree  of  contraction,  in 
order  to  preserve  the  balance  of  the  body,  must  be  accurately  pro- 
portioned to  that  of  the  others.  In  the  motions  of  walking  and 
running,  or  in  the  still  more  delicate  movements  of  the  hands  and 
fingers,  this  harmony  of  muscular  action  becomes  still  more  evident, 
and  is  seen  also  to  be  absolutely  indispensable  to  the  efficiency  of 
the  muscular  apparatus. 

The  opinion  which  locates  the  above  harmonizing  or  associating 
power  in  the  cerebellum  was  first  suggested  by  the  effects  observed 


CEREBELLUM.  '  431 

after  experimentally  injuring  or  destroying  this  part  of  the  brain. 
If  the  cerebellum  be  exposed  in  a  living  pigeon,  and  a  portion  of 
its  substance  removed,  the  animal  exhibits  at  once  a  peculiar  un- 
certainty in  his  gait,  and  in  the  movement  of  his  wings.  If  the 
injury  be  more  extensive,  he  loses  altogether  the  power  of  flight, 
and  can  walk,  or  even  stand,  only  with  great  difficulty.  This  is  not 
owing  to  any  actual  paralysis,  for  the  movements  of  the  limbs  are 
exceedingly  rapid  and  energetic ;  but  is  due  to  a  peculiar  want  of 
control  over  the  muscular  contractions,  precisely  similar  to  that 
which  is  seen  in  a  man  in  a  state  of  intoxication.  The  movements 
of  the  legs  and  wings,  though  forcible  and  rapid,  are  confused  and 
blundering ;  so  that  the  animal  cannot  direct  his  steps  to  any  par- 
ticular spot,  nor  support  himself  in  the  air  by  flight.  He  reels  and 
tumbles,  but  can  neither  walk  nor  fly. 

Fig.  142. 


Pigeon,  after  Removal  of  the  Cekebellum. 

The  senses  and  intelligence  at  the  same  time  are  unimpaired.  It 
is  extremely  curious,  as  first  remarked  by  Longet,  to  compare  the 
different  phenomena  produced  by  removal  of  the  cerebrum  and 
that  of  the  cerebellum.  If  we  do  these  operations  upon  two  dif- 
ferent pigeons,  and  place  the  animals  side  by  side,  it  will  be  seen 
that  the  first  pigeon,  from  whom  the  cerebrum  only  has  been  re- 
moved, remains  standing  firmly  upon  his  feet,  in  a  condition  of 
complete  repose ;  and  that  when  aroused  and  compelled  to  stir,  he 


4:32  *  THE    BRAIN". 

moves  sluggishly  and  -unwillingly,  but  otherwise  acts  in  a  perfectly 
natural  manner.  The  second  pigeon,  on  the  other  hand,  from 
whom  the  cerebellum  only  has  been  taken  away,  is  in  a  constant 
state  of  agitation.  He  is  easily  terrified,  and  endeavors,  frequently 
with  violent  struggles,  to  escape  the  notice  of  those  who  are 
watching  him;  but  his  movements  are  sprawling  and  unnatural, 
and  are  evidently  no  longer  under  the  effectual  control  of  the  will. 
(Fig.  142.)  If  the  entire  cerebellum  be  destroyed,  the  animal  is 
no  longer  capable  of  assuming  or  retaining  any  natural  posture. 
His  legs  and  wings  are  almost  constantly  agitated  with  ineffectual 
struggles,  which  are  evidently  voluntary  in  character,  but  are  at 
the  same  time  altogether  irregular  and  confused.  Death  generally 
takes  place  after  this  operation  within  twenty-four  hours. 

We  have  often  performed  the  above  operation,  and  always  with 
the  same  effect.  Indeed  there  are  few  experiments  that  have  been 
tried  upon  the  nervous  system,  which  give  results  so  uniform  and 
so  constant  as  this.  Taken  by  themselves,  these  results  would 
invariably  sustain  the  theory  of  Flourens,  which,  indeed,  is  founded 
entirely  upon  them. 

But  we  have  met  with  another  very  important  fact,  in  this  respect, 
which  has  hitherto  escaped  notice.  That  is,  that  birds,  which  have 
lost  their  power  of  muscular  co-ordination  from  injury  of  the  cere- 
bellum, may  recover  this  2)0wer  in  process  of  time,  notAvithstanding  that 
a  large  portion  of  the  cerebellum  has  been  permanently  removed. 
Usually  such  an  operation  upon  the  cerebellum,  as  we  have  men- 
tioned above,  is  fatal  within  twenty-four  hours,  probably  on  account 
of  the  close  proximity  of  the  medulla  oblongata.  But  in  some 
instances,  the  pigeons  upon  which  we  have  operated  have  survived, 
and  in  these  "cases  the  co-ordinating  power  became  re-established. 

In  the  first  of  these  instances,  about  two-thirds  of  the  cerebellum 
was  taken  away,  by  an  opening  in  the  posterior  part  of  the  cranium. 
Immediately  after  the  operation,  the  animal  showed  all  the  usual 
effects  of  the  operation,  being  incapable  of  flying,  walking,  or  even 
standing  still,  but  reeled  and  sprawled  about  in  a  perfectly  helpless 
manner.  In  the  course  of  five  or  six  days,  however,  he  had  regained 
a  very  considerable  control  over  the  voluntary  movements,  and  at 
the  end  of  sixteen  days  his  power  of  muscular  co-ordination  was 
so  nearly  perfect,  that  its  deficiency,  if  any  existed,  was  impercep- 
tible. He  was  then  killed ;  and  on  examination,  it  was  foand  that 
his  cerebellum  remained  in  nearly  the  same  condition  as  immediately 
after  the  operation ;  about  two-thirds  of  its  substance  being  deficient, 


CEREBELLUM. 


433 


and  no  attempt  having  been  made  at  regeneration  of  the  lost  parts. 
The  accompanying  figures,  143  to  146,  show  the  appearances,  in 
this  case,  as  compared  with  the  brain  of  a  healthy  pigeon. 

We  have  also  met  with  three  other  cases,  similar  to  the  above,  in 
which  about  one-half  of  the  cerebellum  was  removed  by  operation. 
The  loss  of  co-ordinating  power,  immediately  after  the  operation, 
though  less  complete  than  in  the  instance  above  mentioned,  was 
perfectly  well  marked  in  character ;  and  in  little  more  than  a  fort- 


Fi?.  143. 


FiV.  144. 


-^ 


Brain  of  Heai-tht  Pigeon— Profile 
view. — 1.  Hemisphere.  2.  Optic  tubercle.  .'3. 
Cerebellum.     4.  Optic  nerve.     5.  Medulla  ob- 

luogata. 

Fiir.  145. 


Brain  of  Operated  Pigeon — 
Profile  view — sliowiug  the  mutilatioa 
of  cerebellum. 

Fi^.  14(3. 


Brain  of   Healtuy    P i g e o n— Po.ste- 
rior  view. 


Brain  of  Operated  Pigeo n — 
Posterior  view — showing  the  mutila- 
tion of  cerebellum. 


night  the  animals  had  nearly  or  quite  recovered  the  natural  control 
of  their  motions. 

These  instances  show,  accordingly,  that  a  large  portion  of  the 
cerebellum  may  be  wanting  without  a  corresponding  deficiency  of 
the  co-ordinating  power.  If  the  theory  of  Flourens  be  correct, 
therefore,  these  cases  can  only  be  explained  by  supposing  that 
those  parts  of  the  cerebellum  which  remain  gradually  become  en- 
abled to  supply  the  place  of  those  which  are  removed.  It  is  more 
probable,  however,  that  the  loss  of  co-ordinating  power,  which  is 
immediately  produced  by  taking  away  a  considerable  portion  of 
this  nervous  centre,  is  to  be  regarded  rather  as  the  eflect  of  the 
sudden  injury  to  the  cerehellum  as  a  whole,  than  as  due  to  the  mere 
removal  of  a  portion  of  its  mass. 
28 


434  THE    BRAIjST. 

Morbid  alterations  of  the  cerebellum,  furtbermore,  particularly 
of  a  chronic  nature,  such  as  slow  inflammations,  abscesses,  tumors, 
&c.,  have  often  been  observed  in  the  human  subject,  without  giving 
rise  to  any  marked  disturbance  of  the  voluntary  movements. 

On  the  other  hand,  many  facts  derived  from  comparative  anatomy 
seem  to  favor  the  opinion  of  Flourens.  If  we  compare  different 
classes  of  animals  with  each  other,  as  fish  with  reptiles,  or  birds 
with  quadrupeds,  in  which  the  development  and  activity  of  the 
entire  nervous  system  vary  extremely,  the  results  of  the  comparison 
will  be  often  contradictory.  But  if  the  comparison  be  made  be- 
tween different  species  in  which  the  general  structure  and  plan  of 
organization  are  similar,  we  often  find  the  development  of  the  cere- 
bellum to  correspond  very  closely  with  the  perfection  and  variety 
of  the  voluntary  movements.  The  frog,  for  example,  is  an  aquatic 
reptile,  provided  with  anterior  and  posterior  extremities;  but  its 
movements,  though  rapid  and  vigorous,  are  exceedingly  simple  in 
character,  consisting  of  little  else  than  flexion  and  extension  of  the 
posterior  limbs.  The  cerebellum  in  this  animal  is  exceedingly 
small,  as  compared  with  the  rest  of  the  brain ;  being  nothing  more 
than  a  thin,  narrow  ribbon  of  nervous  matter,  stretched  across  the 
upper  part  of  the  fourth  ventricle.  In  the  common  turtle  we  have 
another  aquatic  reptile,  where  the  movements  of  swimming,  diving, 
progression,  &c.,  are  accomplished  by  the  consentaneous  action  of 
anterior  and  posterior  extremities,  and  where  the  motions  of  the 
head  and  neck  are  also  much  more  varied  than  in  the  frog.  In 
this  instance  the  cerebellum  is  very  much  more  highly  developed 
than  in  the  former.  In  the  alligator,  again,  a  reptile  whose  motions, 
both  of  the  head,  limbs,  and  tail,  approach  very  closely  to  those  of 
the  quadrupeds,  the  cerebellum  is  still  larger  in  proportion  to  the 
remaining  ganglia  of  the  encephalon. 

The  complete  function  of  the  cerebellum,  accordingly,  as  a  nerv- 
ous centre,  cannot  be  regarded  as  positively  ascertained ;  but  so  far 
as  we  may  rely  on  the  results  of  direct  experiment,  this  organ  has 
evidently  such  an  intimate  and  peculiar  connection  with  the  volun- 
tary movements,  that  a  sudden  and  extensive  injury  inflicted  upon 
its  substance  is  always  followed  by  an  immediate,  though  tempo- 
rary, disturbance  of  the  co-ordinating  power. 

TUBERCULA  QuADRiGEMiNA.  —  These  bodies,  notwithstanding 
their  small  size,  are  very  important  in  regard  to  their  function. 
They  give  origin  to  the  optic  nerves,  and  preside,  as  ganglia,  over 


TUBERCULA    QU ADRIGEMINA.  435 

the  sense  of  sight ;  on  which  account  they  are  also  known  bj  the 
name  of  the  "  optic  ganglia."  Their  development  corresponds  very 
closely  with  that  of  the  external  organs  of  vision.  Thus,  they  are 
large  in  fish,  reptiles,  and  birds,  in  which  the  eyeball  is  for  the 
most  part  very  large  in  proportion  to  the  entire  head;  and  are  small 
in  quadrupeds  and  in  man,  where  the  eyeball  is,  comparatively 
speaking,  of  insignificant  size.  Direct  experiment  also  shows  the 
close  connection  between  the  tubercula  quadrigemina  and  the  sense 
of  sight.  Section  of  the  optic  nerve  at  any  point  between  the 
retina  and  the  tubercles,  produces  complete  blindness ;  and  destruc- 
tion of  the  tubercles  themselves  has  the  same  effect.  But  if  the 
division  be  made  between  the  tubercles  and  the  cerebrum,  or  if  the 
cerebrum  itself  be  taken  away  while  the  tubercles  are  left  un- 
touched, vision,  as  we  have  already  seen,  still  remains.  It  is  the 
tubercles,  therefore,  in  which  the  impression  of  light  is  perceived. 
So  long  as  these  ganglia  are  uninjured  and  retain  their  connection 
with  the  eye,  vision  remains.  As  soon  as  this  connection  is  cut 
offj  or  the  ganglia  themselves  are  injured,  the  power  of  vision  is 
destroyed. 

The  tubercula  quadrigemina  not  only  serve  as  nervous  centres 
for  the  perception  of  light,  but  a  reflex  action  also  takes  place 
through  them,  by  which  the  quantity  of  light  admitted  to  the  eye 
is  regulated  to  suit  the  sensibility  of  the  pupil.  In  darkness  and 
in  twilight,  or  wherever  the  light  is  obscure  and  feeble„the  pupil 
is  enlarged  by  relaxation  of  its  circular  fibres,  so  as  to  admit  as 
large  a  quantity  of  light  as  possible.  On  first  coming  into  a  dark 
room,  accordingly,  everything  is  nearly  invisible ;  but  gradually, 
as  the  pupil  dilates  and  as  more  light  is  admitted,  objects  begin  to 
show  themselves  with  greater  distinctness,  and  at  last  we  can  see 
tolerably  well  in  a  place  where  we  were  at  first  unable  to  perceive 
a  single  object.  On  the  other  hand,  when  the  eye  is  exposed  to  an 
unusually  brilliant  light,  the  pupil  contracts  and  shuts  out  so  much 
of  it  as  would  be  injurious  to  the  retina. 

The  above  is  a  reflex  action,  in  which  the  impression  received  by 
the  retina  is  transmitted  along  the  optic  nerve  to  the  tubercula 
quadrigemina.  From  the  tubercles,  a  motor  impulse  is  then  sent 
out  through  the  motor  nerves  of  the  eye  and  the  filaments  dis- 
tributed to  the  iris,  and  a  contraction  of  the  pupil  takes  place  in 
consequence.  The  optic  nerves  act  here  as  sensitive  fibres,  which 
convey  the  impression  from  the  retina  to  the  ganglion ;  and  if 
they  be  irritated  in  any  part  of  their  course  with  the  point  of  a 


436 


THE    BRAIISr. 


needle,  ttie  result  is  a  contraction  of  tlie  pupil.  This  influence  is 
not  communicated  directly  from  the  nerve  to  the  iris,  but  is  first 
sent  inward  to  the  tubercles,  to  be  afterward  reflected  outward  by 
the  motor  nerves.  So  long  as  the  eyeball  remains  in  connection 
with  the  brain,  mechanical  irritation  of  the  optic  nerve,  as  we  have 
shown  above,  causes  contraction  of  the  pupil ;  but  if  the  nerve  be 
divided,  and  the  extremity  which  remains  in  connection  with  the 
eyeball  be  subjected  to  irritation,  no  effect  upon  the  pupil  is  pro- 
duced. 

The  anatomical  arrangement  of  the  optic  nerves,  and  the  connec- 
tions of  the  optic  tubercles,  are  modified  in  a  remarkable  degree  in 
different  animals,  to  correspond  with  the  position  of  the  two  eyes. 
In  fish,  for  example,  the  eyes  are  so  placed,  on  opposite  sides  of  the 
head,  that  their  axes  cannot  be  brought  into  parallelism  with  each 
other,  and  the  two  eyes  can  never  be  directed  together  at  the  same 
object.  In  these  animals,  the  optic  nerves  cross  each  other  at  the 
base  of  the  brain  without  any  intermixture  of  their  fibres ;  that 
from  the  right  optic  tubercle  passing  to  the  left  eye,  and  that  from 
the  left  optic  tubercle  passing  to  the  right  eye.  (Fig.  147.)     The  two 


Fig.  147. 


Fi2.  148. 


IxFERioK  Surface  of  Brain 
OF  Cod. — 1.  Eight  optic  nerve.  2.  Left 
optic  nerve.  3.  Right  optic  tubercle.  4. 
Left  optic  tubercle.  5,  6.  Hemispheres. 
7.  Medulla  oblongata. 


Inferior  Surface  op  Brain  op 
Fowl. — 1.  Eight  optic  nerve.  2  Left  optic 
nerve.  3.  Right  optic  tubercle.  4.  Left 
optic  tubercle.  5,  6.  Hemispheres.  7.  Me- 
dulla oblongata. 


nervous  cords  are  here  totally  distinct  from  each  other  throughout 
their  entire  length ;  and  are  only  connected,  at  the  point  of  cross- 


TUBERCULA    QUADRIGEMTX A , 


437 


ing,  by  intervening  areolar  tissue.  Impressions  made  on  the  right 
eye  must  therefore  be  perceived  on  the  left  side  of  the  brain;  while 
those  which  enter  the  left  eye  are  conveyed  to  the  right  side  of  the 
brain. 

In  birds,  also,  the  axes  of  the  two  eyes  are  so  widely  divergent 
that  an  object  cannot  be  distinctly  in  focus  for  both  of  them  at  the 
same  time.  The  optic  nerves  are  here  united,  and  apparently  sol- 
dered together,  at  their  point  of  crossing ;  but  the  decussation  of 
their  fibres  is  nevertheless  complete.  (Fig.  148.)  The  nervous  fila- 
ments coming  from  the  left  side  pass  altogether  over  to  the  right ; 
and  those  coming  from  the  right  side  pass  over  to  the  left.  The 
result  of  direct  experiment  on  the  crossed  action  of  the  tubercles  in 
these  animals  corresponds  with  the  anatomical  arrangement  of  the 
nervous  fibres.  If  one  of  the  optic  tubercles  be  destroyed  in  the 
pigeon,  complete  blindness  is  at  once  produced  in  the  eye  of  the 
opposite  side ;  but  vision  remains  unimpaired  in  the  eye  of  the  side 
on  which  the  injury  was  inflicted. 

Fi2.  14ft. 


CocRSB  OF  Optic  N  Ku  vivH  I  N  Ma.v.  — 1,  2    Eight  and  left  eyeballs.     3.    Decussation  or  optic 
Ltfrve^.     4,  4.  Tubercula  quadrigemiua. 


In  the  human  subject,  on  the  other  hand,  where  the  visual  axes 
arc  parallel,  and  where  both  eyes  are  simultaneously  directed  toward 


438  THE    BRAIN. 

the  same  object,  the  optic  nerves  decussate  with  each  other  in  such  a 
manner  as  to  form  a  connection  between  the  two  opposite  sides,  as 
well  as  between  each  tubercle  and  retina  of  the  same  side.  (Fig. 
149.)  This  decussation,  which  is  somewhat  complicated,  takes  place 
in  the  following  manner.  From  each  optic  tubercle  three  difi'erent 
bundles  or  "  tracts"  of  nervous  fibres  are  given  off.  One  set  passes 
across  transversely  at  the  point  of  decussation,  and,  turning  back- 
ward, terminates  in  the  tubercle  of  the  opposite  side ;  another,  cross- 
ing diagonally,  continues  onward  to  the  opposite  eyeball ;  while  a 
third  passes  directly  forward  to  the  eyeball  of  the  same  side.  A 
fourth  set  of  fibres,  still,  passes  across  in  front  of  the  decussation, 
from  the  retina  of  one  eye  to  that  of  the  opposite  side.  We  have, 
therefore,  by  this  arrangement,  the  two  retinae,  as  well  as  the  two 
optic  tubercles,  connected  with  each  other  by  commissural  fibres ; 
while  each  tubercle  is,  at  the  same  time,  connected  both  with  its 
own  retina,  and  with  that  of  the  opposite  side.  It  is  undoubtedly 
owing  to  these  connections  that  when,  in  the  human  subject,  the 
eyes  are  directed  in  their  proper  axes,  the  two  retinae,  as  well  as 
the  two  optic  tubercles,  act  as  a  single  organ.  Yision  is  single, 
therefore,  though  there  are  two  images  upon  the  retinae.  Double, 
vision  occurs  only  when  the  eyeballs  are  turned  out  of  their  proper 
direction,  so  that  the  parallelism  of  their  axes  is  lost,  and  the  image 
no  longer  falls  upon  corresponding  parts  of  the  two  retinae. 

Tuber  Annulare. — The  collection  of  gray  matter  imbedded  in 
the  deeper  portions  of  the  tuber  annulare  occupies  a  situation  near 
the  central  part  of  the  brain,  and  lies  directly  in  the  course  of  the 
ascending  fibres  of  the  anterior  and  posterior  columns  of  the  cord. 
This  ganglion  is  immediately  connected  with  the  functions  of  sensa- 
tion and  voluntary  motion.  We  have  already  seen  that  these  func- 
tions are  not  destroyed  by  taking  away  the  cerebrum,  and  that  they 
also  remain  after  removal  of  the  cerebellum.  According  to  the  ex- 
periments of  Longet,  even  after  complete  removal  of  the  olfactory 
ganglia,  the  cerebrum,  cerebellum,  optic  tubercles,  corpora  striata 
and  optic  thalami,  and  when  nothing  remains  in  the  cavity  of  the 
cranium  but  the  tuber  annulare  and  the  medulla  oblongata,  the 
animal  is  still  sensitive  to  external  impressions,  and  will  still  en- 
deavor by  voluntary  movements  to  escape  from  a  painful  irritation. 
The  same  observer  has  found,  however,  that  as  soon  as  the  ganglion 
of  the  tuber  annulare  is  broken  up,  all  manifestations  of  sensation 
and  volition  cease,  and  even  consciousness  no  longer  appears  to 


MEDULLA    OBLONGATA.  439 

exist.  The  only  movements  which  then  follow  external  irritation 
are  the  occasional  convulsive  motions  which  are  due  to  reflex  action 
of  the  spinal  cord,  and  which  may  be  readily  distinguished  from 
those  of  a  voluntary  character.  The  animal,  under  these  circum- 
stances, is  to  all  appearance  reduced  to  the  condition  of  a  dead 
body,  except  for  the  movements  of  respiration  and  circulation, 
which  still  go  on  for  a  certain  time.  The  tuber  annulare  must 
therefore  be  regarded  as  the  ganglion  by  which  impressions,  con- 
veyed inward  through  the  nerves,  are  first  converted  into  conscious 
sensations;  and  in  which  the  voluntary  impulses  originate,  which 
stimulate  the  muscles  to  contraction. 

We  must  carefully  distinguish,  however,  in  this  respect,  a  simple 
sensation  from  the  ideas  to  which  it  gives  origin  in  the  mind,  and 
the  mere  act  of  volition  from  the  train  of  thought  which  leads  to 
it.  Both  these  purely  mental  operations  take  place,  as  we  have 
seen,  in  the  cerebrum ;  for  mere  sensation  and  volition  may  exist 
independently  of  any  intellectual  action,  as  they  may  exist  after 
the  cerebrum  has  been  destroyed.  A  sensation  may  be  felt  for 
example,  without  our  having  the  power  of  thoroughly  appreciatino- 
it,  or  of  referring  it  to  its  proper  source.  This  condition  is  often 
experienced  in  a  state  of  deep  sleep,  when,  the  body  being  exposed 
to  cold,  or  accidentally  placed  in  a  constrained  position,  we  feel  a 
sense  of  suffering  without  being  able  to  understand  its  cause.  We 
may  even,  under  such  circumstances,  execute  voluntary  movements 
to  escape  the  cause  of  annoyance ;  but  these  movements,  not  being 
directed  by  any  active  intelligence,  fail  of  accomplishing  their  ob- 
ject. We  therefore  remain  in  a  state  of  discomfort  until,  on  awak- 
ening, the  activity  of  the  reason  and  judgment  is  restored,  when  the 
offending  cause  is  at  once  removed. 

We  distinguish,  then,  between  the  simple  power  of  sensation, 
and  the  power  of  fully  appreciating  a  sensitive  impression  and  of 
drawing  a  conclusion  from  it.  We  distinguish  also  between  the 
intellectual  process  which  leads  us  to  decide  upon  a  voluntary 
movement,  and  the  act  of  volition  itself.  The  former  must  precede, 
the  latter  must  follow.  The  former  takes  place,  so  far  as  experi- 
ment can  show,  in  the  cerebral  hemispheres ;  the  latter,  in  the  gan- 
glion of  the  tuber  annulare. 

Medulla  Oblongata. — The  last  remaining  ganglion  of  the  en- 
cephalon  is  that  of  the  medulla  oblongata.  This  ganglion,  it  will 
be  remembered,  is  imbedded  in  the  substance  of  the  restiform  body, 


440  THE    BRAIN. 

occupying  the  lateral  and  posterior  portions  of  tlie  medulla,  at  the 
point  of  origin  of  the  pneumogastric  nerves.  This  portion  of  the 
brain  has  long  been  known  to  be  particularly  essential  to  the  pre- 
servation of  life ;  so  that  it  has  received  the  name  of  the  "  vital 
point,"  or  the  "  vital  knot."  All  the  other  parts  of  the  brain  may 
be  injured  or  removed,  as  we  have  already  seen,  without  the  imme- 
diate and  necessary  destruction  of  life ;  but  so  soon  as  the  medulla 
oblongata  is  broken  up,  and  its  ganglion  destroyed,  respiration 
ceases  instantaneously,  and  the  circulation  also  soon  comes  to  an 
end.  Eemoval  of  the  medulla  oblongata  produces,  therefore,  as  its 
immediate  and  direct  result,  a  stoppage  of  respiration :  and  death 
takes  place  principally  as  a  consequence  of  this  fact. 

Flourens  and  Longet  have  determined,  with  considerable  accu- 
racy, the  precise  limits  of  this  vital  spot  in  the  medulla  oblongata. 
Flourens  ascertained  that  in  rabbits  it  extended  from  just  above 
the  origin  of  the  pneumogastric  nerve,  to  a  level  situated  three  lines 
and  a  half  below  this  origin.  In  larger  animals,  its  extent  is  pro- 
portionally increased.  Longet  ascertained,  furthermore,  that  the 
properties  of  the  medulla  were  not  the  same  throughout  its  entire 
thickness ;  but  that  its  posterior  and  anterior  parts  might  be  de- 
stroyed with  comparative  impunity,  the  peculiarly  vital  spot  being 
confined  to  the  intermediate  portions.  This  vital  point  accordingly 
is  situated  in  the  layer  of  gray  matter,  imbedded  in  the  thickness 
of  the  restiform  bodies,  which  has  been  previously  spoken  of  as 
giving  origin  to  the  pneumogastric  nerves. 

The  precise  nature  of  the  connection  between  this  ganglion  and 
the  function  of  respiration  may  be  described  as  follows.  The 
movements  of  respiration,  which  follow  each  other  with  incessant 
regularity  through  the  whole  period  of  life,  are  not  voluntary 
movements.  We  may  to  a  certain  extent,  hasten  or  retard  them 
at  will,  but  our  power  over  them,  even  in  this  respect,  is  extremely 
limited ;  and  in  point  of  fact  they  are  performed,  during  the  greater 
part  of  the  time,  in  a  perfectly  quiet  and  regular  manner,  without 
our  volition  and  even  without  our  consciousness.  They  continue 
uninterruptedly  through  the  deepest  slumber,  and  even  in  a  con- 
dition of  insensibility  from  accident  or  disease. 

These  movements  are  the  result  of  a  reflex  action  taking  place 
through  the  medulla  oblongata.  The  impression  which  gives  rise 
to  them  originates  principally  in  the  lungs,  from  the  accumulation 
of  carbonic  acid  in  the  pulmonary  vessels  and  air-cells,  is  trans- 
mitted by  the  pneumogastric  nerves  to  the  medulla,  and  is  thence 


MEDULLA  oblongata:  441 

reflected  along  tlie  motor  nerves  to  the  respiratory  muscles.  These 
muscles  are  then  called  into  action,  producing  an  expansion  of 
the  chest.  The  impression  so  conveyed  to  the  medulla  is  usually 
unperceived  by  the  consciousness.  It  is  generally  converted  directly 
into  a  motor  impulse,  without  attracting  our  attention  or  giving 
rise  to  any  conscious  sensation.  Respiration,  accordingly,  goes  on 
perfectly  well  without  our  interference  and  without  our  knowledge. 
The  nervous  impression,  however,  conveyed  to  the  medulla,  though 
usually  imperceptible,  may  be  made  evident  at  any  time  by  volun- 
tarily suspending  the  respiration.  As  the  carbonic  acid  begins  to 
accumulate  in  the  blood  and  in  the  lungs,  a  peculiar  sensation  makes 
itself  felt,  which  grows  stronger  and  stronger  with  every  moment, 
and  impels  us  to  recommence  the  movements  of  inspiration.  This 
peculiar  sensation,  entirely  different  in  character  from  any  other,  is 
designated  by  the  French  under  the  name  of  "  besoin  de  respirer," 
It  becomes  more  urgent  and  distressing,  the  longer  respiration  is 
suspended,  until  finally  the  impulse  to  expand  the  chest  can  no 
longer  be  resisted  by  any  effort  of  the  will. 

During  ordinary  respiration,  therefore,  each  inspiratory  move- 
ment is  excited  by  the  partial  vitiation  of  the  air  contained  in  the 
lungs.  As  soon  as  a  new  supply  has  been  inhaled,  the  impulse  to 
respire  is  satisfied,  the  muscles  relax,  and  the  chest  collapses.  In 
a  few  seconds  the  previous  condition  recurs  and  the  same  move- 
ments are  repeated,  producing  in  this  way  a  regular  alternation  of 
inspirations  and  expirations. 

Since  the  movements  of  respiration  are  performed  partly  by  the 
diaphragm  and  partly  by  the  intercostal  muscles,  they  will  be 
differently  modified  by  injuries  of  the  nervous  system,  according  to 
the  spot  at  which  the  injury  is  inflicted.  If  the  spinal  cord,  for 
example,  be  divided  or  compressed  in  the  lower  part  of  the  neck, 
all  the  intercostal  muscles  will  be  necessarily  paralyzed,  and  respi- 
ration will  then  be  performed  entirely  by  the  diaphragm.  The 
chest  in  these  cases  remaining  motionless,  and  the  abdomen  alone 
rising  and  falling  with  the  movements  of  the  diaphragm,  such 
respiration  is  called  "abdominal"  or  "diaphragmatic"  respiration. 
It  is  a  common  symptom  of  fracture  of  the  spine  in  the  lower 
cervical  region.  If  the  phrenic  nerve,  on  the  other  hand,  be 
divided,  the  diaphragm  will  be  paralyzed,  and  respiration  will  then 
be  performed  altogether  by  the  rising  and  falling  of  the  ribs.  It 
is  then  called  "thoracic"  or  "costal"  respiration.  If  the  injury 
inflicted  upon  the  spinal  cord  be  above  the  origin  of  the  second 


442  THE    BRAIN. 

and  third  cervical  nerves,  botli  the  phrenic  and  intercostal  nerves 
are  at  once  paralyzed,  and  death  necessarily  takes  place  from  suf- 
focation. The  attempt  at  respiration,  however,  still  continues  in 
these  cases,  showing  itself  by  ineffectual  inspiratory  movements  of 
the  mouth  and  nostrils.  Finally,  if  the  medulla  itself  be  broken  up 
by  a  steel  instrument  introduced  through  the  foramen  magnum,  so 
as  to  destroy  the  nervous  centre  in  which  the  above  reflex  action 
takes  place,  both  the  power  and  the  desire  to  breathe  are  at  once 
taken  away.  No  attempt  is  made  at  inspiration,  there  is  no  strug- 
gle, and  no  appearance  of  suffering.  The  animal  dies  simply  by 
a  want  of  aeration  of  the  blood,  which  leads  in  a  few  moments  to 
an  arrest  of  the  circulation. 

It  is  owing  to  the  above  action  of  the  medulla  oblongata  that  in- 
juries of  this  part  are  so  promptly  and  constantly  fatal.  When  the 
"  neck  is  broken,"  as  in  hanging  or  by  sudden  falls  upon  the  head, 
a  rupture  takes  place  of  the  transverse  ligament  of  the  atlas ;  the 
head,  together  with  the  first  cervical  vertebra,  is  allowed  to  slide 
forward,  and  the  medulla  is  compressed  between  the  odontoid  pro- 
cess of  the  axis  in  front  and  the  posterior  part  of  the  arch  of  the 
atlas  behind.  In  cases  of  apoplexy,  where  any  part  of  the  hemi- 
spheres, corpora  striata,  or  optic  thalami,  is  the  seat  of  the  hemor- 
rhage, the  patient  generally  lives  at  least  twelve  hours ;  but  if  the 
hemorrhage  takes  place  into  the  medulla  itself,  or  at  the  base  of  the 
brain  in  its  immediate  neighborhood,  so  as  to  compress  its  sub- 
stance, death  follows  instantaneously,  and  by  the  same  mechanism 
as  where  the  medulla  is  intentionally  destroyed. 

An  irregularity  or  want  of  correspondence  in  the  movements  of 
respiration  is  accordingly  found  to  be  one  of  the  most  threatening 
of  all  symptoms  in  affections  of  the  brain.  A  disturbance  or  sus- 
pension of  the  intellectual  powers  does  not  indicate  necessarily  any 
immediate  danger  to  life.  Even  sensation  and  volition  may  be  im- 
paired without  serious  and  direct  injury  to  the  organic  functions. 
These  symptoms  only  indicate  the  threatening  progress  of  the  dis- 
ease, and  show  that  it  is  gradually  approaching  the  vital  centre.  It 
is  common  to  see,  however,  as  the  medulla  itself  begins  to  be  impli- 
cated, a  paralysis  first  showing  itself  in  the  respiratory  movements 
of  the  nostrils  and  lips,  while  those  of  the  chest  and  abdomen  still 
go  on  as  usual.  The  cheeks  are  then  drawn  in  with  every  inspira- 
tion and  puffed  out  sluggishly  with  every  expiration,  the  nostrils 
themselves  sometimes  participating  in  these  unnatural  movements. 
A  still  more  threatening  symptom,  and  one  which  frequently  pre- 


MEDULLA    OBLONGATA.  443 

cedes  death,  is  an  irregular,  hesitating  respiration,  which  sometimes 
attracts  the  attention  of  the  physician,  even  before  the  remaining 
cerebral  functions  are  seriously  impaired.  These  phenomena  de- 
pend on  the  connection  between  the  respiratory  movements  and  the 
reflex  action  of  the  medulla  oblongata. 

We  have  now,  in  studying  the  functions  of  various  parts  of  the 
cerebro-spinal  system,  become  familiar  with  three  difierent  kinds  of 
reflex  action. 

The  first  is  that  of  the  spinal  cord.  Here,  there  is  no  proper 
sensation  and  no  direct  consciousness  of  the  act  which  is  performed. 
It  is  simply  a  nervous  impression,  coming  from  the  integument, 
and  transformed  by  the  gray  matter  of  the  spinal  cord  into  a  motor 
impulse  destined  for  the  muscles.  This  action  will  take  place  after 
the  removal  of  the  hemispheres  and  the  abolition  of  consciousness, 
as  well  as  in  the  ordinary  condition.  The  respiratory  action  of  the 
medulla  oblongata  is  of  the  same  general  character ;  that  is,  it  is 
not  necessarily  connected  with  either  volition  or  consciousness. 
The  only  peculiarity  in  this  instance  is  that  the  original  nervous 
impression  is  of  a  special  character,  and  its  influence  is  finally 
exerted  upon  a  special  muscular  apparatus.  Actions  of  this  nature 
are  termed,  par  excellence,  reflex  actions. 

The  second  kind  of  reflex  action  takes  place  in  the  tuber  annu- 
lare. Here  the  nervous  impression,  which  is  conveyed  inward 
from  the  integument,  instead  of  stopping  at  the  spinal  cord,  passes 
onward  to  the  tuber  annulare,  where  it  first  gives  rise  to  a  con- 
scious sensation;  and  this  sensation  is  immediately  followed  by  a 
voluntary  act.  Thus,  if  a  crumb  of  bread  fall  into  the  larynx,  the 
sensation  produced  by  it  excites  the  movement  of  coughing.  The 
sensations  of  hunger  and  thirst  excite  a  desire  for  food  and  drink. 
The  sexual  impulse  acts  in  precisely  the  same  manner ;  the  percep- 
tion of  particular  objects  giving  rise  immediately  to  special  desires 
of  a  sexual  character. 

It  will  be  observed,  in  these  instances,  that  in  the  first  place, 
the  nervous  sensation  must  be  actually  perceived,  in  order  to  pro- 
duce its  effect;  and  in  the  second  place  that  the  action  which 
follows  is  wholly  voluntary  in  character.  But  the  most  important 
peculiarity,  in  this  respect,  is  that  the  voluntary  impulse  follows 
directly  upon  the  receipt  of  the  sensation.  There  is  no  intermediate 
reasoning  or  intellectual  process.  "We  do  not  cough  because  we 
know  that  this  is  the  most  effectual  way  to  clear  the  larynx ;  but 
simply  because  we  are  impelled  to  do  so  by  the  sensation  which  ia 


444  THE    BRAIN. 

felt  at  the  time.  We  do  not  take  food  or  drink  because  we  know 
that  they  are  necessary  to  support  life,  much  less  because  we  under- 
stand the  mode  in  which  they  accomplish  this  object ;  but  merely 
because  we  desire  them  whenever  we  feel  the  sensation  of  hunger 
and  thirst. 

All  actions  of  this  nature  are  termed  instinctive.  They  are  volun- 
tary in  character,  but  are  performed  blindly ;  that  is,  without  any 
idea  of  the  ultimate  object  to  be  accomplished  by  them,  and  simply 
in  consequence  of  the  receipt  of  a  particular  sensation.  Accord- 
ingly experience,  judgment,  and  adaptation  have  nothing  to  do  with 
these  actions.  Thus  the  bee  builds  his  cell  on  the  plan  of  a  mathe- 
matical figure,  without  performing  any  mathematical  calculation. 
The  silkworm  wraps  himself  in  a  cocoon  of  his  own  spinning, 
certainly  without  knowing  that  it  is  to  afford  him  shelter  during 
the  period  of  his  metamorphosis.  The  fowl  incubates  her  eggs 
and  keeps  them  at  the  proper  temperature  for  development,  simply 
because  the  sight  of  them  creates  in  her  a  desire  to  do  so.  The 
habits  of  these  animals,  it  is  true,  are  so  arranged  by  nature,  that 
such  instinctive  actions  are  always  calculated  to  accomplish  an 
ultimate  object.  But  this  calculation  is  not  made  by  the  animal 
himself,  and  does  not  form  any  part  of  his  mental  operations. 
There  is  consequently  no  improvement  in  the  mode  of  performing 
such  actions,  and  but  little  deviation  under  a  variety  of  circum- 
stances. 

The  third  kind  of  reflex  action  requires  the  co-operation  of  the 
hemispheres.  Here,  the  nervous  impression  is  not  only  conveyed 
to  the  tuber  annulare  and  converted  into  a  sensation,  but,  still 
following  upward  the  course  of  the  fibres  to  the  cerebrum,  it  there 
gives  rise  to  a  special  train  of  ideas.  We  understand  then  the 
external  source  of  the  sensation,  the  manner  in  which  it  is  calcu- 
lated to  affect  us,  and  how  by  our  actions  we  may  turn  it  to  our 
advantage  or  otherwise.  The  action  which  follows,  therefore,  in 
these  cases,  is  not  simply  voluntary  but  reasonable.  It  does  not 
depend  directly  upon  the  external  sensation,  but  upon  an  intellec- 
tual process  which  intervenes  between  the  sensation  and  the  voli- 
tion. These  actions  are  distinguished,  accordingly,  by  a  character 
of  definite  contrivance,  and  a  conscious  adaptation  of  means  to 
ends ;  characteristics  which  do  not  belong  to  any  other  operations 
of  the  nervous  system. 

The  possession  of  this  kind  of  intelligence  and  reasoning  power 
is  not  confined  to  the  human  species.     We  have  already  seen  that 


MEDULLA    OBLOXGATA.  445 

there  are  many  purely  instinctive  actions  in  man,  as  well  as  in 
animals.  It  is  no  less  true  that  in  the  higher  animals  there  is  often 
the  same  exercise  of  reasoning  power  as  in  man.  The  degree  of 
this  power  is  much  less  in  them  than  in  him,  but  its  nature  is  the 
same.  Whenever,  in  an  animal,  we  see  any  action  performed  with 
the  evident  intention  of  accomplishing  a  particular  object,  to  which 
it  is  properly  adapted,  such  an  act  is  plainly  the  result  of  reason- 
ing powers,  not  essentially  different  from  our  own.  The  establish- 
ment of  sentinels  by  gregarious  animals,  to  warn  the  herd  of  the 
approach  of  danger,  the  recollection  of  punishment  inflicted  for  a 
particular  action,  and  the  subsequent  avoidance  or  concealment  of 
that  action,  the  teachability  of  many  animals,  and  their  capacity  of 
forming  new  habits  or  of  improving  the  old  ones,  are  all  instances 
of  the  same  kind  of  intellectual  power,  and  are  quite  different  from 
instinct,  strictly  speaking.  It  is  this  faculty  which  especially  pre- 
dominates over  the  others  in  the  higher  classes  of  animals,  and 
which  finally  attains  its  maximum  of  development  in  the  human 
species. 


446  THE    CRANIAL    NERVES. 


CHAPTER    V. 

THE    CRANIAL    NERVES. 

In  examining  the  cranial  nerves,  we  shall  find  that  although  they 
at  first  seem  quite  different  in  their  distribution  and  properties 
from  the  spinal  nerves,  yet  they  are  in  reality  arranged  for  the 
most  part  on  the  same  plan,  and  may  be  studied  in  a  similar 
manner. 

At  the  outset,  however,  we  find  that  there  are  three  of  the  cra- 
nial nerves,  commonly  so  called,  which  must  be  arranged  in  a  class 
by  themselves ;  since  they  have  no  character  in  common  with  the 
other  nerves  originating  either  from  the  brain  or  the  spinal  cord. 
These  are  the  three  nerves  of  special  sense;  viz.,  the  Olfactory, 
Optic,  and  Auditory.  They  are,  properly  speaking,  not  so  much 
nerves  as  commissures,  connecting  different  parts  of  the  encephalic 
mass  with  each  other.  They  are  neither  sensitive  nor  motor,  in 
the  ordinary  meaning  of  these  terms ;  but  are  capable  of  conveying 
only  the  special  sensation  characteristic  of  the  organ  with  which 
they  are  connected. 

Olfactory  Nerves. — We  have  already  described  the  so-called 
olfactory  nerves  as  being  in  reality  commissures,  connecting  the 
olfactory  ganglia  with  the  central  parts  of  the  brain.  The  masses 
situated  upon  the  cribriform  plate  of  the  ethmoid  bone  are  com- 
posed of  gray  matter;  and  even  the  filaments  which  they  send 
outward  to  be  distributed  in  the  Schneiderian  mucous  membrane, 
are  gray  and  gelatinous  in  their  texture,  and  quite  different  from 
the  fibres  of  ordinary  nerves.  The  olfactory  nerves  are  not  very 
well  adapted  for  direct  experiment.  It  is,  however,  at  least  certain, 
with  regard  to  them  that  they  serve  to  convey  the  special  sensation 
of  smell;  that  their  mechanical  irritation  does  not  give  rise  to 
either  pain  or  convulsions;  and  finally  that  their  destruction, 
together  with  that  of  the  olfactory  ganglia,  does  not  occasion  any 
paralysis  nor  loss  of  ordinary  sensibility. 


THE    CRANIAL   NERVES.  447 

Optic  ISTerves. — We  have  already  given  some  account  of  these 
nerves  and  their  decussations,  in  connection  with  the  history  of  the 
tubercula  quadrigemina.  They  consist  of  rounded  bundles  of  white 
fibres,  running  between  the  tubercles  and  the  retinae.  As  the  reti- 
nae themselves  are  membranous  expansions  consisting  mostly  of 
vesicular  or  cellular  nervous  matter,  the  optic  nerves,  or  "tracts," 
must  be  regarded  as  commissures  connecting  the  retinae  with  the 
tubercles.  We  have  also  seen  that  they  serve,  by  some  of  their 
fibres,  to  connect  the  two  retinge  with  each  other,  as  well  as  the  two 
tubercles  with  each  other. 

The  optic  nerves  convey  only  the  special  imipression  of  light  from 
without  inward,  and  give  origin  to  the  reflex  action  of  the  optic 
tubercles,  by  which  the  pupil  is  made  to  contract.  According  to 
Longet,  the  optic  nerves  are  absolutely  insensible  to  pain  through- 
out their  entire  length.  When  a  galvanic  current  is  passed  through 
the  eyeball,  or  when  the  retina  is  touched  in  operations  upon  the 
eye,  the  irritation  has  been  found  to  produce  the  impression  of  lumi- 
nous sparks  and  flashes,  instead  of  an  ordinary  painful  sensation. 
The  impression  of  colored  rings  or  spots  may  be  easily  produced 
by  compressing  the  eye  in  particular  directions;  and  a  sudden 
stroke  upon  the  eyeball  will  often  give  rise  to  an  apparent  discharge 
of  brilliant  sparks.  Division  of  the  optic  nerves  produces  complete 
blindness,  but  does  not  destroy  ordinary  sensibility  in  any  part  of 
the  eye,  nor  occasion  any  muscular  paralysis. 

Auditory  Nerves. — The  nervous  expansion  in  the  cavity  of 
the  internal  ear  contains,  like  the  retina,  vesicles  or  cells  as  well  as 
fibres ;  and  the  auditory  nerves  are  therefore  to  be  regarded,  like 
the  optic  and  olfactory,  as  commissural  in  their  character.  They 
are  also,  like  the  preceding,  destitute  of  ordinary  sensibility.  Ac- 
cording to  Longet,  they  may  be  injured  or  destroyed  without  giving 
rise  to  any  sensation  of  pain.  They  serve  to  convey  to  the  brain 
the  special  sensation  of  sound,  and  seem  incapable  of  transmitting 
any  other.  Longet'  relates  an  experiment  performed  by  Yolta,  in 
which,  by  passing  a  galvanic  current  through  the  ears,  the  observer 
experienced  the  sensation  of  an  interrupted  hissing  noise,  so  long 
as  the  connection  of  the  wires  was  maintained.  Inflammations 
within  the  ear,  or  in  its  neighborhood,  are  often  accompanied  by 
the  perception  of  various   noises,  like  the  ringing  of  bells,  the 

'  Traits  de  Physiologie,  vol.  ii.  p  286. 


448 


THE    CRANIAL    NERViSS. 


washing  of  the  waves,  the  humming  of  insects ;  sounds  which  have 
no  external  existence,  but  which  are  simulated  by  the  morbid  irri- 
tation of  the  auditory  nerve. 

It  is  evident,  from  the  facts  detailed  above,  that  the  nerves  of 
special  sense  are  neither  motor  or  sensitive,  properly  speaking; 
and  that  they  are  distinct  in  their  nature  from  the  ordinary  spinal 
nerves. 

The  remainder  of  the  cranial  nerves,  however,  present  the 
ordinary  qualities  belonging  to  the  spinal  nerves.  Some  of  them 
are  exclusively  motor  in  character,  others  exclusively  sensitive; 
while  most  of  them  exhibit  the  two  properties,  to  a  certain  extent, 
as  mixed  nerves.  They  may  be  conveniently  arranged  in  three 
pairs,  according  to  the  regions  in  which  they  are  distributed,  cor- 
responding very  closely  with  the  motor  and  sensitive  roots  of  the 
spinal  nerves.  According  to  such  a  plan,  the  arrangement  of  the 
cranial  nerves  would  be  as  follows : — 


Motor  nerves. 

'  Motor  oculi  com.  ") 

Patheticus  I 

1st  PAIR.  \   Motor  oc.  externns         i- 

Small  root  of  5th  pair   i 

t  Facial  J 

2d  PAIR.         Hypoglossal 

3d  PAIR.        Spinal  accessory 


Cranial  Nerves. 
Nerves  of  Special  Sense. 
Olfactory.     2.  Optic.     3.  Auditory. 

Sensitive  Nerves. 


Distributed  to 


Large  root  of  5th  pair.         Face. 


Glosso-pharyngeal. 
Pneuniogastric. 


Tongue. 

Neck,  &c. 


The  above  arrangement  of  the  cranial  nerves  is  not  absolutely 
perfect  in  all  its  details.  Thus,  while  the  hypoglossal  supplies  the 
muscles  of  the  tongue  alone,  the  glosso-pharyngeal  sends  part  of 
its  sensitive  fibres  to  the  tongue  and  part  to  the  pharynx ;  and 
while  the  large  root  of  the  5th  pair  is  mostly  distributed  in  the 
face,  one  of  its  branches,  viz.,  the  gustatory,  is  distributed  to  the 
tongue.  Notwithstanding  these  irregularities,  however,  the  above 
division  of  the  cranial  nerves  is  in  the  main  correct,  and  will  be 
found  extremely  useful  as  an  assistant  in  the  study  of  their  func- 
tions. 

There  is  no  impropriety,  moreover,  in  regarding  all  the  motor 
branches  distributed  upon  the  face  as  one  nerve ;  since  even  the 
anterior  roots  of  the  spinal  nerves  originate  from  the  spinal  cord, 
each  by  several  distinct  filaments,  which  are  associated  into  a  single 


THE    CKANIAL    NERVES.  449 

bundle  only  at  a  certain  distance  from  their  point  of  origin.  The 
mere  fact  that  two  nerves  leave  the  cavity  of  the  cranium  by  the 
same  foramen  does  not  indicate  that  they  have  the  same  or  even  a 
similar  function.  Thus  the  facial  and  auditory  both  escape  from 
the  cavity  of  the  cranium  by  the  foramen  auditorium  internum,  and 
yet  we  do  not  hesitate  to  regard  them  as  entirely  distinct  in  their 
nature  and  functions.  It  is  the  ultimate  distribution  of  a  nerve, 
and  not  its  course  through  the  bones  of  the  skull,  that  indicates 
its  physiological  character  and  position.  For  while  the  ultimate 
distribution  of  any  particular  nerve  is  always  the  same,  its  arrange- 
ment as  to  trunk  and  branches  may  vary,  in  different  species 
of  animals,  with  the  anatomical  arrangement  of  the  bones  of  the 
skull.  This  is  well  illustrated  by  a  fact  first  pointed  out  by  Prof. 
Jeffries  Wyman*  in  the  anatomy  of  the  nervous  system  of  the 
bullfrog.  In  this  animal,  both  the  facial  nerve  and  motor  oculi 
externus,  instead  of  arising  as  distinct  nerves,  are  actually  given 
off  as  branches  of  the  5th  pair ;  while  their  ultimate  distribution  is 
the  same  as  in  other  animals.  All  the  motor  and  sensitive  nerves 
distributed  to  the  face  are  accordingly  to  be  regarded  as  so  many 
different  branches  of  the  same  trunk ;  varying  sometimes  in  their 
course,  but  always  the  same  in  their  ultimate  distribution. 

The  motor  nerves  of  the  head  are  in  all  respects  identical  in  their 
properties  with  the  anterior  roots  of  the  spinal  nerves.  For,  in  the 
first  place,  they  are  distributed  to  muscles,  and  not  to  the  integu- 
ment or  to  mucous  membranes;  secondly,  their  division  causes 
muscular  paralysis;  and  thirdly,  mechanical  irritation  applied  at 
their  origin  produces  muscular  contraction  in  the  parts  to  which 
they  are  distributed,  but  does  not  give  rise  to  a  painful  sensa- 
tion. In  several  instances,  nevertheless,  the  motor  nerves,  though 
insensible  at  their  origin,  show  a  certain  degree  of  sensibility  when 
irritated  after  their  exit  from  the  skull,  owing  to  fibres  of  com- 
munication which  they  receive  from  the  purely  sensitive  nerves. 
In  this  respect  they  resemble  the  spinal  nerves,  the  motor  and 
sensitive  filaments  of  which  are  at  first  distinct  in  the  anterior 
and  posterior  roots,  but  afterward  mingle  with  each  other,  on 
leaving  the  cavity  of  the  spinal  canal. 

The  three  sensitive  nerves   originating   from  the  brain  are  the 

'  Nervons  System  of  Rana  pipiens  ;  published  by  the  Smithsonian  Institution. 
Washington,  1853. 
29 


450  THE    CRANIAL    NERVES. 

large  root  of  the  fifth  pair,  the  glosso-pharyngeal,  and  the  pneumo- 
gastric.  It  will  be  observed  that,  in  all  their  essential  properties, 
they  correspond  with  the  posterior  roots  of  the  spinal  nerves.  Like 
them  they  are  inexcitable,  but  extremely  sensitive.  Irritated  at 
their  point  of  origin,  they  give  rise  to  acutely  painful  sensations, 
but  to  no  convulsive  movements.  Secondly,  if  divided  at  the  same 
situation,  the  operation  is  followed  by  loss  of  sensibility  in  the 
parts  to  which  they  are  distributed,  without  any  disturbance  of  the 
motive  power.  Each  of  these  nerves,  furthermore,  like  the  poste- 
rior root  of  a  spinal  nerve,  is  provided  with  a  ganglion  through 
which  its  fibres  pass :  the  fifth  pair,  with  the  Casserian  ganglion, 
situated  near  the  inner  extremity  of  the  petrous  portion  of  the  tem- 
poral bone;  the  glosso-pharyngeal,  with  the  ganglion  of  Andersch, 
situated  in  the  jugular  fossa;  while  the  pneumogastric  presents, 
just  before  its  passage  through  the  jugular  foramen,  a  ganglion 
known  as  the  ganglion  of  the  pneumogastric  nerve.  Finally,  the 
sensitive  fibres  of  all  these  nerves,  beyond  the  situation  of  their  gan- 
glia, are  intermingled  with  others  of  a  motor  origin.  The  large  root 
of  the  fifth  pair,  which  is  exclusively  sensitive,  is  accompanied  by 
the  fibres  of  the  small  root,  which  are  exclusively  motor.  The 
glosso-pharyngeal  receives  motor  filaments  from  the  facial  and  spi- 
nal accessory,  becoming  consequently  a  mixed  nerve  outside  the 
cranial  cavity ;  while  the  pneumogastric  is  joined  by  fibres  from  the 
spinal  accessory  and  various  other  nerves  of  a  motor  character. 
These  nerves,  accordingly,  are  exclusively  sensitive  only  at  their 
point  of  origin.  Though  they  afterward  retain  the  predominating 
character  of  sensitive  nerves,  they  are  yet  found,  if  irritated  in  the 
middle  of  their  course,  to  be  intermingled  with  motor  fibres,  and 
to  have  consequently  acquired,  to  a  certain  extent,  the  character  of 
mixed  nerves. 

The  resemblance,  therefore,  between  the  cranial  and  spinal  nerves 
is  complete. 

Motor  Oculi  Communis. — This  nerve,  which  is  sometimes  known 
by  the  more  convenient  name  of  the  oculo-motorius,  originates  from 
the  inner  edge  of  the  crus  cerebri,  passes  into  the  cavity  of  the 
orbit  by  the  sphenoidal  fissure,  and  is  distributed  to  the  levator 
palpebrse  superioris,  and  to  all  the  muscles  moving  the  eyeball, 
except  the  external  rectus  and  the  superior  oblique.  Its  irritation 
accordingly  produces  convulsive  movements  in  these  parts,  and 


FIFTH    PAIR.  451 

its  division  lias  the  effect  of  paralyzing  the  muscles  to  which  it  is 
distributed.  The  superior  eyelid  falls  down  over  the  pupil,  and 
cannot  be  raised,  owing  to  the  inaction  of  its  levator  muscle,  so 
that  the  eye  appears  constantly  half  shut.  This  condition  is  known 
by  the  name  of  "  ptosis."  The  movements  of  the  eyeball  are  also 
nearly  suspended,  and  permanent  external  strabismus  takes  place, 
owing  to  the  paralysis  of  the  internal  rectus  muscle,  while  the  ex- 
ternal rectus,  animated  by  a  different  nerve,  preserves  its  activity. 

Patheticcs. — This  nerve,  which  supplies  the  superior  oblique 
muscle  of  the  eyeball,  is  similar  in  its  general  properties  to  the  pre- 
ceding. Its  section  causes  paralysis  of  the  above  muscle,  without 
any  loss  of  sensibility. 

Motor  Externus. — This  nerve,  the  sixth  pair,  according  to  the 
usual  anatomical  arrangement,  is  distributed  to  the  external  rectus 
muscle  of  the  eyeball.  Its  division  or  injury  by  disease  is  followed 
by  internal  strabismus,  owing  to  the  unopposed  action  of  the  internal 
rectus  muscle. 

Fifth  Pair. — This  is  one  of  the  most  important  and  remarkable 
in  its  properties  of  all  the  cranial  nerves.  It  is  the  great  sensitive 
nerve  of  the  face,  and  of  the  adjoining  mucous  membranes.  Its 
larger  root,  after  emerging  from  the  outer  and  under  surface  of  the 
pons  Varolii,  passes  forward  over  the  inner  extremity  of  the  petrous 
portion  of  the  temporal  bone.  It  there  expands  into  a  crescentic- 
shaped  swelling,  containing  a  quantity  of  gray  matter  with  which 
its  fibres  are  intermingled,  and  which  is  known  as  the  Casserian 
ganglion.  The  fibres  of  the  smaller  root,  passing  forward  in  com- 
pany with  the  others,  do  not  take  any  part  in  the  formation  of  this 
ganglion,  but  may  be  seen  passing  beneath  it  as  a  distinct  bundle, 
and  continuing  their  course  forward  to  the  foramen  ovale,  through 
which  they  emerge  from  the  skull.  In  front  of  the  anterior  and 
external  border  of  the  Casserian  ganglion,  the  fifth  nerve  separates 
into  three  principal  divisions,  viz.,  the  ophthalmic,  the  superior 
maxillary,  and  the  inferior  maxillary.  The  first  of  these  divisions, 
viz.,  the  ophthalmic,  is  so  called  because  it  passes  through  the  orbit 
of  the  eye.  It  enters  the  sphenoidal  fissure,  and  runs  along  the 
upper  portion  of  the  orbit,  sending  branches  to  the  ophthalmic  gan- 
glion of  the  sympathetic,  to  the  lachrymal  gland,  the  conjunctiva, 


452 


THE    CRANIAL    NERVES. 


Fig.  150. 


and  the  mucous  membrane  of  the  lachrymal  sac.  It  also  sends  off 
a  small  branch  (nasal  branch)  which  penetrates  into  the  nasal  pas- 
sages and  supplies  the  Schneiderian  mucous  membrane.  It  then 
emerges  upon  the  face  by  the  supra-orbital  foramen,  and  is  distri- 
buted to  the  integument  of  the  forehead  and  side  of  the  head  as  far 
back  as  the  vertex. 

The  second  division  of  this  nerve,  or  the  superior  maxillary^ 
passes  out  by  the  foramen  rotundum,  and  runs  along  the  longitu- 
dinal canal  in  the  floor  of  the  orbit,  giving  off  branches  during  its 
passage  to  the  teeth  of  the  upper  jaw  and  to  the  mucous  membrane 
of  the  antrum  maxillare.  It  finally  emerges  upon  the  middle  of  the 
face  by  the  infra-orbital  foramen,  and  is  distributed  to  the  integu- 
ment of  the  lower  eyelid,  nose,  cheek,  and  upper  lip. 

The  third,  or  inferior  maxillary  division  of  the  fifth  pair,  which 
is  the  largest  of  the  three,  leaves  the  cavity  of  the  cranium  by  the 

foramen  ovale.  It  comprises  a  con- 
siderable portion  of  the  large  root 
of  the  nerve,  and  all  the  fibres  of 
the  small  root.  This  division  is 
therefore  a  mixed  nerve,  containing 
both  motor  and  sensitive  fibres, 
while  the  two  former  are  exclu- 
sively sensitive.  It  is  distributed, 
accordingly,  both  to  muscles  and 
to  the  sensitive  surfaces.  Soon  after 
emerging  from  the  foramen  ovale 
it  sends  branches  to  the  temporal 
muscle,  to  the  masseter,  the  bucci- 
nator, and  to  the  internal  and  ex- 
ternal pterygoids;  that  is,  to  the 
muscles  which  are  particularly  con- 
cerned in  the  movements  of  the 
lower  jaw.  It  also  sends  sensitive 
filaments  to  the  integument  of  the 
temple,  to  that  of  a  portion  of  the  external  ear  and  external  audi- 
tory meatus.  The  third  division  of  the  fifth  pair,  then  passing 
downward  and  forward,  gives  off  a  branch  of  considerable  size,  the 
lingual  branch,  which  is  distributed  to  the  mucous  membrane  of  the 
anterior  two-thirds  of  the  tongue,  and  which  also  sends  filaments  to 
the  arches  of  the  palate  and  to  the  mucous  membrane  of  the  cheek. 


Distribution  of  Fifth  Nehve 
rpON  THE  Face. — n.  Casserian  «^<inglion. 
1.  Ophthalmic  division.  2.  Superior  maxil- 
lary division.    3.  Inferior  maxillary  di  vision. 


FIFTH    PAIR.  453 

The  remaining  portion  of  the  third  division,  after  giving  a  few 
branches  to  the  mylo-hyoid  muscle  and  to  the  anterior  belly  of  the 
digastric,  then  enters  the  inferior  dental  canal,  sends  filaments  to 
the  teeth  of  the  lower  jaw,  emerges  at  the  mental  foramen,  and  is 
finally  distributed  to  the  integument  of  the  chin,  lower  lip,  and 
inferior  part  of  the  face. 

This  nerve  is  accordingly  distributed  to  the  sensitive  surfaces, 
that  is,  the  integument  and  mucous  membranes  about  the  face,  and 
to  the  muscles  of  mastication.  A  few  of  its  fibres  are  sent  also  to 
the  superficial  muscles  of  the  face,  such  as  the  buccinator  and  the 
orbicularis  oris;  but  these  fibres  are  sensitive  in  their  character, 
and  serve  merely  to  impart  to  the  muscles  a  certain  degree  of 
sensibility.  It  has  been  ascertained  by  Longet  that  if  the  various 
branches  of  this  nerve  be  irritated  by  a  galvanic  current,  no  con- 
vulsive movements  whatever  are  produced  in  those  superficial 
muscles  of  the  face,  which  it  supplies  with  filaments;  but  if  its 
smaller  or  non-ganglionic  root  be  irritated  in  the  same  way,  con- 
tractions instantly  follow  in  the  muscles  of  mastication. 

The  fifth  pair  is  the  most  acutely  sensitive  nerve  in  the  whole 
body.  Its  irritation  by  mechanical  means  always  causes  intense 
pain,  and  even  though  the  animal  be  nearly  unconscious  from  the 
influence  of  ether,  any  severe  injury  to  its  large  root  is  almost 
invariably  followed  by  cries  which  indicate  the  extreme  sensibility 
of  its  fibres. 

If  this  nerve  be  completely  divided,  in  the  living  animal,  within 
the  cranium,  at  the  situation  of  the  Casserian  ganglion,  the  operation 
is  followed  by  total  loss  of  sensibility  in  the  skin  of  the  face  and  in 
the  adjacent  mucous  membranes.  The  conjunctiva,  upon  the  affected 
side,  is  then  completely  insensible,  and  may  be  touched  with  the 
point  of  a  needle  or  the  blade  of  a  knife,  without  exciting  any  un- 
easiness, and  even  without  the  consciousness  of  the  animal.  Probes 
and  needles  may  be  passed  into  the  nostril,  and  the  lips  or  the 
cheek  may  be  pinched,  pierced  or  cut,  without  exciting  the  least 
sign  of  sensibility.  The  animal  is  entirely  indifferent  to  all  me- 
chanical injuries  upon  the  affected  side,  though  upon  the  opposite 
side  the  parts  retain  their  natural  sensibility. 

Owing  to  the  paralysis  of  the  lingual  nerve,  also,  after  this  ope- 
ration, the  tongue,  in  its  anterior  two-thirds,  becomes  insensible  to 
ordinary  irritations,  and  loses,  beside,  the  power  of  taste. 

Another  peculiar  effect  of  the  division  of  the  fifth  pair  depends 


454:  THE    CRANIAL    NERVES. 

upon  the  paralysis  of  its  motor  fibres,  which  are  distributed,  as  we 
have  seen,  to  the  muscles  of  mastication.  In  many  of  the  lower 
animals,  consequently,  the  movements  of  mastication  become  ex- 
ceedingly enfeebled  upon  the  affected  side.  In  the  cat,  for  example, 
an  animal  in  which  mastication  is  usually  very  thoroughly  per- 
formed, this  process  becomes  excessively  laborious,  so  that  the 
animal  after  this  operation  cannot  masticate  solid  meat,  but  requires 
to  be  fed  with  that  which  has  already  been  cut  in  pieces. 

The  fifth  pair,  beside  supplying  the  sensibility  of  the  integument 
of  the  face,  has  a  peculiar  and  important  influence  on  the  organs  of 
special  sense.  This  influence  appears  to  consist  in  some  connection 
between  the  action  of  the  fifth  pair  and  the  processes  of  nutrition ; 
so  that  when  the  former  is  injured,  the  latter  very  soon  become 
deranged.  For  the  perfect  action  of  any  one  of  the  organs  of 
special  sense,  two  conditions  are  necessary :  first,  the  sensibility  of 
the  special  nerve  belonging  to  it,  and  secondly,  the  integrity  of  the 
component  parts  of  the  organ  itself.  Now  as  the  nutrition  of  the 
organ  is,  to  a  certain  extent,  under  the  control  of  the  fifth  pair,  any 
serious  injury  to  this  nerve  produces  a  derangement  in  the  tissues 
of  the  organ,  and  consequently  interferes  with  the  due  performance 
of  its  function. 

The  mucous  membrane  of  the  nasal  passages,  for  example,  is 
supplied  by  two  different  nerves;  first,  the  olfactory,  distributed 
throughout  its  upper  portion,  by  which  it  is  endowed  with  the 
special  sense  of  smell ;  and,  secondly,  the  nasal  branch  of  the  fifth 
pair,  distributed  throughout  its  middle  and  lower  portions,  by 
which  it  is  supplied  with  ordinary  sensibility. 

Since  the  fifth  pair,  accordingly,  supplies  general  sensibility  to 
the  nasal  passages,  this  property  will  remain  after  the  special  sense 
of  smell  has  been  destroyed.  If,  however,  the  fifth  pair  itself  be 
divided,  not  only  is  general  sensibility  destroyed  in  the  Schneiderian 
mucous  membrane,  but  a  disturbance  begins  to  take  place  in  the 
nutrition  of  its  tissue,  by  which  it  is  gradually  rendered  unfit  for 
the  performance  of  its  special  function,  and  the  power  of  smell  is 
finally  lost.  The  mucous  membrane,  under  these  circumstances, 
becomes  injected  and  swollen,  and  the  nasal  passage  is  obstructed 
by  an  accumulation  of  puriform  mucus.  According  to  Longet,  the 
mucous  membrane  also  assumes  a  fungous  consistency,  and  is  liable 
to  bleed  at  the  slightest  touch.  The  effect  of  this  alteration  is  to 
blunt  or  altogether  destroy  the  sense  of  smell.  It  is  owing  to  a 
similar  unnatural  condition  of  the  mucous  membrane  that  the  power 


FIFTH    PAIR.  455 

of  smell  is  always  more  or  less  impaired  in  cases  of  coryza  and 
influenza.  The  olfactory  nerves  become  inactive  in  consequence 
of  the  morbid  alteration  in  their  mucous  membrane,  and  in  the 
secretions  which  cover  it. 

The  influence  of  this  nerve  over  the  organ  of  vision  is  still  more 
remarkable.  It  has  been  known  for  many  years  that  division  of 
the  fifth  pair  within  the  cranium,  or  of  its  ophthalmic  branch,  is  fol- 
lowed by  an  inflammation  of  the  corresponding  eye,  which  usually 
goes  on  to  complete  and  permanent  destruction  of  the  organ. 
Immediately  after  the  operation,  the  pupil  becomes  contracted  and 
the  conjunctiva  loses  its  sensibility.  At  the  end  of  twenty -four 
hours,  the  cornea  begins  to  become  opaline,  and  by  the  second 
day  the  conjunctiva  is  already  inflamed  and  begins  to  discharge  a 
purulent  secretion.  The  inflammation,  after  commencing  in  the 
conjunctiva,  increases  in  intensity  and  soon  spreads  to  the  iris, 
which  becomes  covered  with  a  layer  of  inflammatory  exudation. 
The  cornea  grows  constantly  more  opaque,  until  it  is  at  last 
altogether  impermeable  to  light,  and  vision  is  consequently  sus- 
pended. Blipdness,  therefore,  does  not  result  in  these  instances 
from  any  direct  affection  of  the  optic  nerve  or  of  the  retina,  but  is 
owing  simply  to  opacity  of  the  cornea.  Sometimes  the  diseased 
action  goes  on  until  it  results  in  ulceration  of  the  cornea  and  dis- 
charge of  the  humors  of  the  eye ;  sometimes,  after  the  lapse  of 
several  days,  the  inflammatory  appearances  subside,  and  the  eye  is 
finally  restored  to  its  natural  condition. 

It  has  been  observed,  however,  that  although  the  above  conse- 
quences always  follow  division  of  the  fifth  pair,  when  performed  at 
the  level  of  the  Casserian  ganglion,  or  between  it  and  the  eyeball, 
they  are  either  much  diminished  in  intensity  or  altogether  wanting 
when  the  division  is  made  at  a  point  posterior  to  the  ganglion. 
This  circumstance  has  led  to  the  belief  that  the  influence  of  the  fifth 
pair  on  the  nutrition  of  the  eyeball  does  not  reside  in  its  own  proper 
fibres,  but  in  some  filaments  of  the  sympathetic  nerve  which  join 
the  fifth  pair  at  the  level  of  the  Casserian  ganglion.  If  the  section 
accordingly  be  made  at  this  point,  or  in  front  of  it,  the  fibres  of  the 
sympathetic  will  be  divided  with  the  others,  and  inflammation  of 
the  eye  will  result ;  but  if  the  section  be  made  behind  the  ganglion, 
the  fibres  of  the  sympathetic  will  escape  division,  and  the  injurious 
effects  upon  the  eye  will  be  wanting.  Such  is  the  explanation 
usually  given  of  the  above-mentioned  facts;  but  the  question  has 
not  as  yet  been  determined  in  a  positive  manner. 


456  THE    CRANIAL    NERVES. 

Division  of  the  fiftli  pair  destroys  also  the  general  sensibility  of 
the  external  auditory  meatus,  the  lining  membrane  of  which  is 
supplied  by  its  filaments.  Inflammation  of  this  membrane  and  its 
consequent  alterations,  it  is  well  known,  interfere  seriously  with 
the  sense  of  hearing.  It  is  no  uncommon  occurrence  for  an  accu- 
mulation of  cerumen  to  take  place  after  inflammation  of  this  part, 
so  as  to  block  up  the  auditory  canal  and  produce  partial  or  com- 
plete deafness.  It  has  not  been  ascertained,  however,  whether 
division  of  the  fifth  pair  is  usually  followed  by  similar  changes  in 
this  part. 

The  lingual  branch  of  the  fifth  pair  supplies  the  anterior  ex- 
tremity and  middle  portion  of  the  tongue  both  with  general  sensi- 
bility and  with  the  power  of  taste.  The  sensibility  of  the  tongue 
is  accordingly  provided  for  by  two  different  nerves ;  in  its  anterior 
two-thirds,  by  the  lingual  branch  of  the  fifth  pair ;  in  its  posterior 
third,  by  the  fibres  of  the  glosso-pharyngeal. 

The  facial  branches  of  the  fifth  pair  are  the  ordinary  seat  of  tic 
douloureux.  This  affection  is  not  unfrequently  confined  to  either 
the  supra-orbital,  the  infra-orbital,  or  the  mental  branch ;  and  the 
pain  may  be  accurately  traced  in  the  direction  of  their  diverging 
fibres.  It  has  already  been  mentioned  that  the  painful  sensations 
sometimes  also  follow  the  course  of  the  facial,  owing  to  some  sensi- 
tive filaments  which  that  nerve  receives  from  the  fifth  pair. 

Facial. — This  nerve  was  known  to  the  older  anatomists  as  the 
"portio  dura  of  the  seventh  pair."  It  leaves  the  cavity  of  the 
cranium  by  the  internal  auditory  foramen,  in  company  with  the 
auditory  nerve ;  and,  as  the  latter  is  of  a  softer  consistency  than  the 
former,  they  have  received  the  names  respectively  of  the  "  portio 
mollis"  and  "  portio  dura"  of  the  seventh  pair.  There  is,  however, 
no  physiological  connection  between  these  two  nerves ;  for  while 
the  auditory  is  spread  out  in  the  cavity  of  the  internal  ear,  the  facial 
passes  onward  through  the  petrous  portion  of  the  temporal  bone, 
emerges  at  the  stylo-mastoid  foramen,  bends  round  beneath  the 
external  ear,  and  passes  forward  through  the  substance  of  the 
parotid  gland,  forming  a  plexus  called  the  "pes  anserinus,"  by  the 
abundant  inosculation  of  its  different  branches.  It  then  sends  its 
filaments  forward  in  a  diverging  course,  and  is  finally  distributed 
to  the  muscles  of  the  external  ear,  to  the  frontalis  and  superciliaris 
muscles,  to  the  orbicularis  oculi,  the  compressors  and  dilators  of 
the  nares,  the  orbicularis  oris,  and  to  the  elevators  and  depressors 


FACIAL    NERVE. 


457 


Fig.  151. 


Facial   Nebve. 


of  the  lips ;  tliat  is,  to  the  superficial  muscles  of  the  face,  which  are 
concerned  in  the  production  of  expression.  (Fig.  151.) 

The  facial,  consequently,  is  the 
motor  nerve  of  the  face.  It  has 
nothing  to  do  with  transmitting 
sensitive  impressions,  since  it  has 
been  frequently  shown  that  after 
section  of  the  fifth  pair,  the  facial 
remaining  entire,  the  sensibility  of 
the  face  is  completely  lost ;  so  that 
the  integument  may  be  cut,  pricked, 
pierced,  or  lacerated,  without  any 
sign  of  pain  being  exhibited  by  the 
animal.  The  facial,  therefore,  does 
not  transmit  sensation  from  these 
parts ;  and  its  division,  which  was 
formerly  resorted  to  in  cases  of 
tic  douloureux,  is  accordingly  alto- 
gether incapable  of  relieving  neuralgic  pains. 

This  nerve,  however,  is  directly  connected  with  muscular  action, 
since  mechanical  or  galvanic  irritation  of  its  fibres  produces  con- 
vulsive twitching  in  the  ears,  nostrils,  lips,  and  cheeks. 

If  the  facial  nerve  be  divided  in  one  of  the  lower  animals,  as,  for 
example,  in  the  cat,  immediately  after  its  emergence  from  the 
stylo-mastoid  foramen,  it  will  be  found .  that  complete  muscular 
paralysis  has  occurred  in  all  those  parts  to  which  the  nerve  is  dis- 
tributed, while  the  power  of  sensation  remains  unimpaired.  The 
animal  is  incapable  of  moving  the  ear,  which  remains  constantly  in 
the  same  position.  There  is  also  incapacity  of  closing  the  eyelids, 
owing  to  paralysis  of  the  orbicularis  oculi,  and  the  eye  accordingly 
remains  constantly  open,  even  when  the  opposite  eye  is  closed ; 
as  during  sleep,  or  in  the  act  of  winking.  If  the  conjunctiva  be 
touched,  the  animal  feels  the  irritation,  and  endeavors  to  escape 
from  it ;  but  the  eyeball  is  only  drawn  partially  backward  into  the 
socket  by  the  action  of  the  recti  muscles,  and  the  third  eyelid 
pushed  partly  across  the  cornea.  The  complete  closure  of  the  eye 
is  impossible.  It  will  be  observed,  accordingly,  that  precisely  oppo- 
site effects  are  produced  upon  the  eyelids  by  paralysis  of  the  oculo- 
motorius  nerve,  and  by  that  of  the  facial.  In  the  former  instance, 
owing  to  the  paralysis  of  the  levator  palpebrae  superioris,  the  eye 
is  always  partially  closed ;  in  the  latter,  owing  to  paralysis  of  the 


458  THE    CRANIAL    NERVES. 

orbicularis,  it  is  always  partially  open.  The  movements  of  tLe 
nares  are  also  suspended  on  tbe  side  of  the  injury,  and  if  the  angle 
of  the  mouth  be  examined  on  that  side,  it  will  be  found  to  hang 
down  lower  than  on  the  opposite  side,  and  to  be  constantly  partly 
open,  owing  to  the  paralysis  of  the  orbicularis  oris  and  the  eleva- 
tors of  the  angle  of  the  mouth. 

These  are  the  only  inconveniences  which  follow  the  division  of 
the  facial  nerve  in  the  cat,  but  in  some  other  of  the  lower  animals, 
where  various  muscular  organs  in  this  region  are  particularly  de- 
veloped, the  consequences  are  more  troublesome.  Thus,  in  the  rabbit, 
the  ear,  upon  the  affected  side,  falls  down,  and  cannot  be  raised  or 
pointed  in  different  directions ;  and  as  the  movements  of  the  ear 
are  important  in  these  animals,  as  aids  to  the  hearing,  the  per- 
fection of  this  sense  must  be  considerably  impaired  by  paralysis  of 
the  facial  nerve.  In  the  horse,  it  has  been  noticed  by  Bernard,' 
that  division  of  the  facial  on  both  sides  is  fatal  by  suffocation.  For 
this  animal  breathes  exclusively  through  the  nostrils,  which  open 
widely  at  the  time  of  inspiration,  to  allow  the  admission  of  air.  If 
these  movements  be  suspended,  by  paralysis  of  the  facial  nerve,  the 
nostrils  immediately  collapse,  and  the  animal  dies  by  suffocation. 

In  the  human  subject,  the  facial  nerve  is  occasionally  paralyzed 
upon  one  side,  sometimes  from  sympathetic  irritation,  sometimes 
from  organic  disease  in  the  petrous  portion  of  the  temporal  bone, 
or  within  the  cranial  cavity  near  the  origin  of  the  nerve.  In  either 
case,  an  extremely  well-marked  affection  is  the  result,  known  as 
"facial  paralysis."  This  condition  is  chiefly  characterized  by  an 
entire  absence  of  expression  on  the  affected  side  of  the  face.  The 
lower  eyelid  sinks  downward,  from  paralysis  of  the  orbicularis 
muscle,  and  cannot  be  closed. 

The  corner  of  the  mouth  also  falls  downward,  and  the  whole 
lower  part  of  the  face  is  drawn  over  to  the  opposite  side,  by  the 
force  of  the  antagonistic  muscles.  The  lips  are  unable  to  retain 
the  fluids  of  the  mouth ;  and  the  saliva  dribbles  away  from  between 
them,  giving  to  the  face  a  remarkably  vacant  and  helpless  appear- 
ance. 

The  principal  inconvenience,  however,  suffered  by  the  human 
subject  in  facial  paralysis,  depends  upon  the  want  of  action  of  the 
muscles  about  the  lips  and  cheek.     In  drinking,  the  fluids  escape 

'  Le(;ons  sur  la  Pliysiologie  et  la  Patliologie  du  Syst^me  Nerveux,  Paris,  1858, 
vol.  ii.  p.  38. 


GLOSSO-niARYNGEAL    NERVE.  459 

by  the  corner  of  the  mouth,  and  in  mastication  the  food  has  partly 
a  tendency  to  escape  by  the  same  opening,  and  partly  accumulates, 
on  the  affected  side,  between  the  gums  and  the  cheek,  owing  to  the 
paralysis  of  the  buccinator  muscle,  which  receives  its  motor  fila- 
ments from  the  facial  nerve.  Thus,  the  action  of  all  the  superficial 
facial  muscles  is  suspended,  the  expression  of  the  face  is  destroyed, 
and  the  movements  of  the  lips  and  the  prehension  of  the  food 
seriously  interfered  with. 

Though  the  facial,  however,  be  essentially  a  motor  nerve,  yet  its 
principal  branches  distributed  to  the  face  have  a  certain  degree  of 
sensibility;  that  is,  when  these  branches  are  irritated  in  the  middle 
of  their  course,  the  animal  immediately  gives  evidence  of  a  painful 
sensation.  Longet  has  shown,  by  an  extremely  ingenious  mode 
of  experiment,'  that  this  sensibility  of  the  branches  of  the  facial 
does  not  depend  on  any  sensitive  fibres  of  their  own,  but  upon 
those  which  they  derive  from  inosculation  with  the  fifth  pair.  He 
exposes,  for  example,  the  facial  nerve  in  the  dog,  and,  irritating  its 
principal  branches  one  after  the  other,  at  each  application  of  the 
irritant  there  are  evident  signs  of  pain.  He  then  divides  the  facial 
nerve  at  its  point  of  exit  from  the  stylo-mastoid  foramen,  and 
finds  that,  after  this  operation,  the  sensibility  of  its  branches  still 
remains.  The  fibres,  accordingly,  upon  which  this  sensibility 
depends,  do  not  pass  out  with  the  trunk  of  the  nerve,  but  are 
derived  from  some  other  source.  The  experimenter,  then,  upon 
another  animal,  divides  the  fifth  pair  within  the  skull,  leaving  the 
facial  untouched;  and  afterward,  on  irritating  as  before  the  ex- 
posed branches  of  the  latter  nerve,  he  finds  that  its  sensibility  has 
entirely  disappeared.  It  is  by  filaments,  accordingly,  derived  from 
the  fifth  pair,  that  a  certain  degree  of  sensibility  is  communicated 
to  the  branches  of  the  facial. 

These  facts  account  for  the  peculiar  circumstance  that,  in  cases 
of  tic  douloureux,  the  spasmodic  pain  sometimes  follows  exactly 
the  course  of  the  facial  nerve,  viz :  from  behind  the  ear  forward 
upon  the  side  of  the  face ;  and  yet  the  section  of  this  nerve  does  not 
put  an  end  to  the  neuralgia,  but  only  causes  paralysis  of  the  facial 
muscles. 

Glosso-PharyNgeal. — This  nerve  originates  from  the  lateral 
portion  of  the  medulla  oblongata,  passes  outward,  and  enters  the 

'  Traitu  de  Physiologie,  vol.  ii.  pp.  354-357. 


460  THE    CRANIAL    NERVES. 

posterior  foramen  lacerum  in  company  with  the  pneumogastric  and 
spinal  accessory.  While  in  the  jugular  fossa  it  presents  a  gangliform 
enlargement,  called  the  ganglion  of  Andersch,  below  the  level  of 
which  it  receives  branches  of  communication  from  the  facial  and 
the  spinal  accessor3\  It  then  runs  downward  and  forward,  and  is 
distributed  to  the  mucous  membrane  of  the  base  of  the  tongue, 
pillars  of  the  fauces,  soft  palate,  middle  ear,  and  upper  part  of  the 
pharynx.  It  also  sends  some  branches  to  the  constrictors  of  the 
pharynx  and  the  neighboring  muscles.  Longet  has  found  this 
nerve  at  its  origin  to  be  exclusively  sensitive ;  but  below  the  level 
of  its  ganglion  it  has  been  found  by  him,  as  well  as  by  various 
other  observers,  to  be  both  sensitive  and  motor,  owing  to  the  fibres 
of  communication  received  from  the  motor  nerves  mentioned  above. 
Its  final  distribution  is,  however,  as  we  have  seen,  principally  to 
sensitive  surfaces.  The  principal  ofiice  of  this  nerve  is  to  impart 
the  sense  of  taste  to  the  posterior  third  of  the  tongue,  to  which  it  is 
distributed.  It  also  presides  over  the  general  sensibility  of  this 
part  of  the  tongue,  as  well  as  that  of  the  fauces  and  pharynx. 

Dr.  John  Keid,^  who  has  performed  a  great  variety  of  experiments 
■upon  this  nerve,  comes  to  the  following  conclusions  in  regard  to  it. 
First,  that  it  is  essentially  a  sensitive  nerve,  since  there  are  unequi- 
vocal signs  of  pain  when  it  is  pricked,  pinched,  or  cut.  Second, 
that  irritation  of  this  nerve  produces  convulsive  movements  of  the 
throat  and  lower  part  of  the  face ;  but  that  these  movements  are,  in 
great  measure,  not  direct,  but  reflex  in  their  character,  since  they 
will  take  place  equally  well  after  the  glosso-pharyngeal  has  been 
divided,  if  the  irritation  be  applied  to  its  cranial  extremity.  Third, 
that  this  nerve  supplies  the  special  sensibility  of  taste  to  a  portion 
of  the  tongue;  but  that  it  is  not  the  exclusive  nerve  of  this  sense, 
since  the  power  of  taste  remains,  after  it  has  been  divided  on  both 
sides. 

There  are  certain  reflex  actions,  furthermore,  which  take  place 
through  the  medium  of  the  glosso-pharyngeal  nerve.  After  the 
food  has  been  thoroughly  masticated,  it  is  carried,  by  the  move- 
ments of  the  tongue  and  sides  of  the  mouth,  through  the  fauces, 
and  brought  in  contact  with  the  mucous  membrane  of  the  pharynx. 
This  produces  an  impression  which,  conveyed  to  the  medulla 
oblongata  by  the  filaments  of  the  glosso-pharyngeal,  excites  the 


In  Todd's  Cyclopaedia  of  Anatomy  and  Physiology,  article   Glosso-pharyngeal 


Nert 


PXEUMOGASTRIC    NERVE.  461 

muscles  of  the  fauces  and  pharynx  by  reflex  action.  The  food  is 
consequently  grasped  by  these  muscles,  without  the  concurrence  of 
the  will,  and  the  process  of  deglutition  is  commenced.  This  action 
is  not  only  involuntary,  but  it  will  frequently  take  place  even  in 
opposition  to  the  will.  The  food,  once  past  the  isthmus  of  the  fauces, 
is  beyond  the  control  of  volition,  and  cannot  be  returned  except  by 
convulsive  action,  equally  involuntary  in  its  character. 

Natural  stimulants,  therefore,  applied  to  the  mucous  membrane 
of  the  pharynx,  excite  deglutition ;  unnatural  stimulants,  applied 
to  the  same  part,  excite  vomiting.  If  the  finger  be  introduced  into 
the  fauces  and  pharynx,  or  if  the  mucous  membrane  of  these  parts 
be  irritated  by  prolonged  tickling  with  the  end  of  a  feather,  the 
sensation  of  nausea,  conveyed  through  the  glosso-pharyngeal  nerve, 
is  sometimes  so  great  as  to  produce  immediate  and  copious  vomit- 
ing. This  method  may  often  be  successfully  employed  in  cases  of 
poisoning,  when  it  is  desirable  to  excite  vomiting  rapidly,  and  when 
emetic  medicines  are  not  at  hand. 

Pneumogastric. — Owing  to  the  numerous  connections  of  the 
pneumogastric  with  other  nerves,  its  varied  and  extensive  distribu- 
tion, and  the  important  character  of  its  functions,  this  is  properly 
regarded  as  one  of  the  most  remarkable  nerves  in  the  whole  body. 
Owing  to  the  wandering  course  of  its  fibres,  which  are  distributed 
to  no  less  than  four  different  vital  organs,  viz.,  the  heart,  lungs, 
stomach  and  liver,  as  well  as  to  several  other  parts  of  secondary 
importance,  it  has  been  often  known  by  the  name  of  the  par  vagum. 
The  pneumogastric  arises,  by  a  number  of  separate  filaments,  from 
the  lateral  portion  of  the  medulla  oblongata,  in  the  groove  between 
the  olivary  and  restiform  bodies.  These  filaments  unite  into  a 
single  trunk,  which  emerges  from  the  cranium  by  the  jugular  fora- 
men, where  it  is  provided  with  a  longitudinal  ganglionic  swelling, 
the  "  ganglion  of  the  pneumogastric  nerve."  Immediately  below 
the  level  of  this  ganglion  the  nerve  receives  an  important  branch 
of  communication  from  the  spinal  accessory,  and  afterward  from 
the  facial,  the  hypoglossal,  and  the  anterior  branches  of  the  first 
and  second  cervicals. 

At  its  origin,  the  pneumogastric  is  exclusively  a  sensitive  nerve. 
Irritated  above  the  situation  of  its  ganglion,  it  has  been  found  to 
convey  painful  sensations  alone ;  but  if  the  irritation  be  applied  at 
a  lower  level,  it  causes  at  the  same  time  muscular  contractions, 
owing  to  the  filaments  which  it  has  received  from  the  above-men- 


%t2  TUE    CRANIAL    NERVES. 

tioned  motor  nerves.  It  becomes,  consequently,  after  emerging 
from  the  cranial  cavity,  a  mixed  nerve ;  and  has,  accordingly,  in 
nearly  all  its  branches,  a  double  distribution,  viz.,  to  the  mucous 
membranes  and  the  muscular  coat  of  the  organs  to  which  it  belongs. 

The  ordinarv  sensibility  of  the  pneu- 
Fie.  l.')2.  ^  .  -^     ,  '^         n  • 

mogastnc  nerve,  however,  as  all  experi- 
menters have  observed,  is  exceedingly 
dull,  in  comparison  with  that  of  the  other 
sensitive  cranial  nerves.  We  have  often 
divided  this  nerve  in  the  middle  of  the 
neck,  without  any  distinct  manifestation 
of  pain  being  given  by  the  animal ;  and 
though  Bernard  has  found  that  at  some 
times  its  sensibility  is  well  marked,  while 
at  others  it  is  very  indistinct,  he  is  not 
able  to  say  upon  what  special  physio- 
logical conditions  this  difference  depends. 
While  the  pneumogastric,  however,  is 
decidedly  deficient,  as  a  general  rule,  in 
ordinary  sensibility,  it  possesses,  as  we 
shall  see  hereafter,  a  sensibility  of  a  pecu- 
liar kind,  which  is  exceedingly  important 
for  the  maintenance  of  the  vital  func- 
tions. 

In  passing  down  the  neck,  this  nerve 
sends  branches  to  the  mucous  membrane 
and  muscular  coat  of  the  pharynx,  oeso- 
phagus, and  respiratory  passages.  Among 
the  most  important  of  these  branches  are 
the  two  laryngeal  nerves,  viz.,  the  supe- 
rior and  inferior.  The  superior  laryngeal 
--.  ,  T,  .       .„     nerve,  which  is  given  off  from  the  trunk 

Diagram    ofPNKUMOOASTRic  '  D 

Nerve,  with uspiincipalbranches.  of  the  pueumogastric  jUSt  after  It  haS 
— 1.  Pharyngeal  branch.     2    Supe-  i      r>  ,i  •,  n    .^  t       ^^ 

rior  laryngeal.     3.  Inferior  laryn-  emerged    from    thc    CaVlty    of    the    skull, 

geai.  4.  Pulmonary  branches.  6.     passcs  dowuward  aud  forward,  pcnetrates 

stomach.    6.  Liver.  ,  ..,.,„ 

the  larynx  by  an  opening  m  the  side  of 
the  thyro-hyoid  membrane,  and  is  distributed  to  the  mucous  mem- 
brane of  the  larynx  and  glottis,  and  also  to  a  single  laryngeal  mus- 
cle, viz.,  the  crico-thyroid.  This  branch  is  therefore  partly  mus- 
cular, but  mostly  sensitive  in  its  distribution.  The  inferior  laryngeal 
branch  is  given  off  just  after  the  pneumogastric  has  entered  the 


PXEUMOGASTRIC    NERVE.  463 

cavity  of  the  chest.  It  curves  round  the  subclavian  artery  on  the 
right  side  and  the  arch  of  the  aorta  on  the  left,  and  ascends  in  the 
groove  between  the  trachea  and  oesophagus,  to  the  larynx.  It 
then  enters  the  larynx  between  the  cricoid  cartilage  and  the  pos- 
terior edge  of  the  thyroid,  and  is  distributed  to  all  the  muscles  of 
the  larynx,  with  the  exception  of  the  crico-thyroid.  This  branch 
is,  therefore,  exclusively  muscular  in  its  distribution. 

The  trunk  of  the  pneumogastric,  after  supplying  the  above 
branches,  as  well  as  sending  numerous  filaments  to  the  trachea 
and  oesophagus  in  the  neck,  gives  off  in  the  chest  its  pulmonary 
branches,  which  follow  the  bronchial  tubes  in  the  lungs  to  their 
minutest  ramifications.  It  then  passes  into  the  abdomen  and  sup- 
plies the  muscular  and  mucous  layers  of  the  stomach,  ramifying 
over  both  the  anterior  and  posterior  surfaces  of  the  organ ;  after 
which  its  fibres  spread  out  and  are  distributed  to  the  liver,  spleen, 
pancreas,  and  gall-bladder. 

The  functions  of  the  pneumogastric  will  now  be  successively 
studied  in  the  various  organs  to  which  it  is  distributed. 

Pharynx  and  (Esophagus. — The  reflex  action  of  deglutition,  which 
has  already  been  described  as  commencing  in  the  upper  part  of  the 
pharynx,  by  means  of  the  glosso-pharyngeal,  is  contintued  in  the 
lower  portion  of  the  pharynx  and  throughout  the  oesGiphagus  by 
the  aid  of  the  pneumogastric.  As  the  food  is  compressed  by  the 
superior  constrictor  muscle  of  the  pharynx  and  forced  downward, 
it  excites  the  mucous  membrane  with  which  it  is  brought  in  -contact 
and  gives  rise  to  another  contraction  of  the  middle  constrictor.  The 
lower  constrictor  is  then  brought  into  action  in  its  turn  in  a  similar 
manner ;  and  a  wave-like  or  peristaltic  contraction  is  thence  pro- 
pagated throughout  the  entire  length  of  the  oesophagus,  by  which 
the  food  is  carried  rapidly  from  above  downward,  and  conducted  at 
last  to  the  stomach.  Each  successive  portion  of  the  mucous  mem- 
brane, in  this  instance,  receives  in  turn  the  stimulus  of  .the  food, 
and  excites  instantly  its  own  muscles  to  contraction;  so  that  the 
food  passes  rapidly  from  one  end  of  the  oesophagus  to  the  other,  by 
an  action  which  is  wholly  reflex  in  character  and  entirely  withdrawn 
from  the  control  of  the  will.  Section  of  the  pneumogastric,  or  of 
its  pharyngeal  and  oesophageal  branches,  destroys  therefore  at  the 
same  time  the  sensibility  and  the  motive  power  of  these  parts.  The 
food  is  no  longer  conveyed  readily  to  the  stomach,  but  accumulates 
in  the  paralyzed  oesophagus,  into  which  it  is  forced  by  the  voluntary 


464  THE    CRANIAL    NERVES. 

movements  of  the  mouth  and  fauces,  and  by  the  continued  action 
of  the  upper  part  of  the  pharynx. 

It  must  be  remembered  that  the  general  sensibility  of  the  oeso- 
phagus is  very  slight,  as  compared  with  that  of  the  integument,  or 
even  of  the  mucous  membranes  near  the  exterior.  It  is  a  general 
rule,  in  fact,  that  the  sensibility  of  the  mucous  membranes  is  most 
acute  at  the  external  orifices  of  their  canals ;  as,  for  example,  at  the 
lips,  anterior  nares,  anus,  orifice  of  the  urethra,  &c.  It  diminishes 
constantly  from  without  inward,  and  disappears  altogether  at  a 
certain  distance  from  the  surface.  The  sensibility  of  the  pharynx 
is  less  acute  than  that  of  the  mouth,  but  is  still  sufficient  to  enable 
us  to  perceive  the  contact  of  ordinary  substances;  while  in  the 
oesophagus  we  are  not  usually  sensible  of  the  impression  of  the  food 
as  it  passes  from  above  downward.  The  reflex  action  takes  place 
here  without  any  assistance  from  the  consciousness ;  and  it  is  only 
when  substances  of  an  unusually  pungent  or  irritating  nature  are 
mingled  with  the  food,  that  its  passage  through  the  oesophagus  pro- 
duces a  distinct  sensation. 

Larynx. — We  have  already  described  the  course  and.  distribution 
of  the  two  laryngeal  branches  of  the  pneumogastric.  The  superior 
laryngeal  nerve  is  principally  the  sensitive  nerve  of  the  larynx. 
Its  division  destroys  sensibility  in  the  mucous  membrane  of  this 
organ,  but  paralyzes  only  one  of  its  muscles,  viz :  the  crico-thyroid. 
Galvanization  of  this  nerve  has  also  been  found  to  induce  con- 
tractions in  the  crico-thyroid,  but  in  none  of  the  other  muscles 
belonging  to  the  larynx.  The  inferior  laryngeal,  on  the  other 
hand,  is  a  motor  nerve.  Its  division  paralyzes  all  the  muscles  of 
the  larynx  except  the  crico-thyroid ;  and  irritation  of  its  divided 
extremity  produces  contraction  in  the  same  muscles.  The  inuscles 
and  mucous  membrane  of  the  larynx  are  therefore  supplied  by  two 
difi'erent  branches  of  the  same  trunk,  viz.,  the  superior  laryngeal 
nerve  for  the  mucous  membrane,  and  the  inferior  laryngeal  nerve 
for  the  muscles. 

The  larynx,  in  man  and  in  all  the  higher  animals,  performs  a 
double  function ;  one  part  of  which  is  connected  with  the  voice,  the 
other  with  respiration. 

The  formation  of  the  voice  in  the  larynx  takes  place  as  follows. 
If  the  glottis  be  exposed  in  the  living  animal,  by  opening  the 
pharynx  and  oesophagus  on  one  side,  and  turning  the  larynx  for- 
ward, it  will  be  seen  that  so  long  as  the  vocal  chords  preserve 
their  usual  relaxed  condition  during  expiration,  no  sound  is  heard. 


PNEUMOGASTRIC    NEKVE.  465 

except  the  ordinary  faint  whisper  of  the  air  passing  gently  through 
the  cavity  of  the  larynx.  When  a  vocal  sound,  however,  is  to  be 
produced,  the  chords  are  suddenly  made  tense  and  applied  closely 
to  each  other,  so  as  to  diminish  very  considerably  the  size  of  the 
orifice;  and  the  air,  driven  by  an  unusually  forcible  expiration 
through  the  narrow  opening  of  the  glottis,  in  passing  between  the 
vibrating  vocal  chords,  is  itself  thrown  into  vibrations  which  pro- 
duce the  sound  required.  The  tone,  pitch,  and  intensity  of  this 
sound,  vary  with  the  conformation  of  the  larynx,  the  degree  of  ten- 
sion and  approximation  of  the  vocal  chords,  and  the  force  of  the 
expiratory  effort.  The  narrower  the  opening  of  the  glottis,  and  the 
greater  the  tension  of  the  chords,  under  ordinary  circumstances,  the 
more  acute  the  sound ;  while  a  wider  opening  and  a  less  degree  of 
tension  produce  a  graver  note.  The  quality  of  the  sound  is  also 
modified  by  the  length  of  the  column  of  air  included  between  the 
glottis  and  the  mouth,  the  tense  or  relaxed  condition  of  the  walls 
of  the  pharynx  and  fauces,  and  the  state  of  dryness  or  moisture  of 
the  mucous  membrane  lining  the  aerial  passages. 

Articulation,  on  the  other  hand,  or  the  division  of  the  vocal  sound 
into  vowels  and  consonants,  is  accomplished  entirely  by  the  lips, 
tongue,  teeth,  and  fauces.  These  organs,  however,  are  under  the 
control  of  other  nerves,  and  the  mechanism  of  their  action  need  not 
occupy  us  here. 

Since  the  production  of  a  vocal  sound,  therefore,  depends  upon 
the  tension  and  position  of  the  vocal  chords,  as  determined  by  the 
action  of  the  laryngeal  muscles,  it  is  not  surprising  that  division  of 
the  inferior  laryngeal  nerves,  by  paralyzing  these  muscles,  should 
produce  a  loss  of  voice.  It  has  been  sometimes  found  that  in  very 
young  animals  the  crico-thyroid  muscles,  which  are  the  only  ones 
not  affected  by  division  of  the  inferior  laryngeal  nerves,  are  still 
sufficient  to  give  some  degree  of  tension  to  the  vocal  chords,  and 
to  produce  in  this  way  an  imperfect  sound ;  but  usually  the  voice 
is  entirely  lost  after  such  an  operation. 

It  is  a  very  remarkable  fact,  however,  in  this  connection,  that  all 
the  motor  filaments  of  the  pneumogastric,  which  are  concerned  in 
the  formation  of  the  voice,  are  derived  from  a  single  source.  It 
will  be  remembered  that  the  pneumogastric,  itself  originally  a 
sensitive  nerve,  receives  motor  filaments,  on  leaving  the  cranial 
cavity,  from  no  less  than  five  different  nerves.  Of  these  filaments, 
however,  those  coming  from  the  spinal  accessory  are  the  only  ones 
necessary  to  the  production  of  vocal  sounds.  For  it  has  been  found 
30 


^QQ  THE    CRANIAL    NERVES. 

bj  Bischoff  and  by  Bernard^  that  if  all  the  roots  of  the  spinal  acces- 
sory be  divided  at  their  origin,  or  if  the  nerve  itself  be  torn  away 
at  its  exit  from  the  skull,  all  the  oth"er  cranial  nerves  remaining 
untouched,  the  voice  is  lost  as  completely  as  if  the  inferior  laryn- 
geal itself  had  been  destroyed.  All  the  motor  fibres  of  the  pneu- 
mogastric,  therefore,  which  act  in  the  formation  of  the  voice  are 
derived,  by  inosculation,  from  the  spinal  accessory  nerve. 

In  respiration,  again,  the  larynx  performs  another  and  still  more 
important  function.  In  the  first  place,  it  stands  as  a  sort  of  guard, 
or'  sentinel,  at  the  entrance  of  the  respiratory  passages,  to  prevent 
the  intrusion  of  foreign  substances.  If  a  crumb  of  bread  accidentally 
fall  within  the  aryteno-epiglottidean  folds,  or  upon  the  edges  of  the 
vocal  chords,  or  upon  the  posterior  surface  of  the  epiglottis,  the 
sensibility  of  these  parts  immediately  excites  a  violent  expulsive 
cough,  by  which  the  foreign  body  is  dislodged.  The  impression 
received  and  conveyed  inward  by  the  sensitive  fibres  of  the  superior 
laryngeal  nerve,  is  reflected  back  upon  the  expiratory  muscles 
of  the  chest  and  abdomen,  by  which  the  instinctive  movements  of 
coughing  are  accomplished.  Touching  the  above  parts  with  the 
point  of  a  needle,  or  pinching  them  with  the  blades  of  a  forceps, 
will  produce  the  same  efi'ect.  This  reaction  is  essentially  dependent 
on  the  sensibility  of  the  laryngeal  mucous  membrane ;  and  it  can 
no  longer  be  produced  after  section  of  the  pneumogastric  nerve,  or 
of  its  superior  laryngeal  branch. 

In  the  second  place,  the  respiratory  movements  of  the  glottis,  already 
described  in  a  previous  chapter,  are  of  the  greatest  importance  to 
the  preservation  of  life.  We  have  seen  that  at  th«  moment  of 
inspiration  the  vocal  chords  are  separated  from  each  other,  and  the 
glottis  opened,  by  the  action  of  the  posterior  crico-arytenoid  muscles ; 
and  that  in  expiration  the  muscles  and  the  vocal  chords  are  both 
relaxed,  and  the  air  allowed  to  pass  out  readily  through  the  glottis. 
The  opening  of  the  glottis  in  inspiration,  therefore,  is  an  active 
movement,  while  its  partial  closure  or  collapse  in  expiration  is  a 
passive  one.  Furthermore,  the  opening  of  the  glottis  in  inspiration 
is  necessary  in  order  to  afford  a  sufficiently  wide  passage  for  the 
air,  in  its  way  to  the  trachea,  bronchi,  and  pulmonary  vesicles. 

Now  we  have  found,  as  Budge  and  Longet  had  previously  no- 
ticed, that  if  the  inferior  laryngeal  nerve  on  the  right  side  be 
divided  while  the  glottis  is  exposed  as  above,  the  respiratory  move- 

•  Recherches  ExpGrimentales  sur  les  fonctions  dii  nerf  spinal.     Paris,  1851. 


PNEUMOGASTRIC    NERVE.  467 

ments  of  tlie  riglit  vocal  chord  instantly  cease,  owing  to  the  para- 
lysis of  the  posterior  crico-arytenoid  muscle  on  that  side.  If  the 
inferior  laryngeal  nerve  on  the  left  side  be  also  divided,  the  para- 
lysis of  the  glottis  is  then  complete,  and  its  respiratory  movements 
cease  altogether.  A  serious  difficulty  in  respiration  is  the  imme- 
diate consequence  of  this  operation.  For  the  vocal  chords,  being 
no  longer  stretched  and  separated  from  each  other  at  the  moment 
of  inspiration,  but  remaining  lax  and  flexible,  act  as  a  double  valve, 
and  are  pressed  inward  by  the  column  of  inspired  air ;  thus  par- 
tially blocking  up  the  passage  and  impeding  the  access  of  air  to 
the  lungs.  If  the  pneumogastrics  be  divided  in  the  middle  of  the 
neck,  the  larynx  is  of  course  paralyzed  precisely  as  after  section 
of  the  inferior  laryngeal  nerves,  since  these  nerves  are  given  off 
only  after  the  main  trunks  have  entered  the  cavity  of  the  chest. 
The  immediate  effect  of  either  of  these  operations  is  to  produce 
a  difficulty  of  inspiration,  accompanied  by  a  peculiar  wheezing  or 
sucking  noise,  evidently  produced. in  the  larynx  and  dependent  on 
the  falling  together  of  the  vocal  chords.  In  very  young  animals, 
as,  for  example,  in  pups  a  few  days  old,  in  whom  the  glottis  is 
smaller  and  the  larynx  less  rigid  than  in  adult  dogs,  this  difficulty 
is  much  more  strongly  marked.  Legallois^  has  even  seen  a  pup 
two  days  old  almost  instantly  suffocated  after  section  of  the  two 
inferior  laryngeal  nerves.  We  have  found  that,  in  pups  two 
weeks  old,  division  of  the  inferior  laryngeals  is  followed  by  death 
at  the  end  of  from  thirty  to  forty  hours,  evidently  from  impeded 
respiration. 

The  importance,  therefore,  of  these  movements  of  the  glottis  in 
respiration  becomes  very  evident.  They  are,  in  fact,  part  and 
parcel  of  the  general  respiratory  movements,  and  are  necessary  to 
a  due  performance  of  the  function.  It  has  been  found,  moreover, 
that  the  motor  filaments  concerned  in  this  action  are  not  derived, 
like  those  of  the  voice,  from  a  single  source.  While  the  vocal 
movements  of  the  larynx  are  arrested,  as  mentioned  above,  by 
division  of  the  spinal  accessory  alone,  those  of  respiration  still  go 
on ;  and  in  order  to  put  a  stop  to  the  latter,  either  the  pneumo-. 
gastrics  themselves  must  be  divided,  or  all  five  of  the  motor  nerves 
from  which  their  accessory  filaments  are  derived.  This  fact  has 
been  noticed  Vjy  Longet  as  showing  that  nature  multiplies  the  safe- 
guards of  a  function  in  proportion  to  its  importance ;  for  while  the 

'  In  Longet's  Traite  de  Phyeiologie,  vol.  ii.  p.  324. 


468  THE    CRANIAL   NERVES. 

spinal  accessory,  or  any  other  one  of  the  above-mentioned  nerves, 
might  be  affected  by  local  accident  or  disease,  it  would  be  very 
improbable  that  any  single  injury  should  paralyze  simultaneously 
the  spinal  accessory,  the  facial,  the  hypoglossal,  and  the  first  and 
second  cervicals.  The  respiratory  movements  of  the  larynx  are 
consequently  much  more  thoroughly  protected  than  those  which 
are  merely  concerned  in  the  formation  of  the  voice. 

Lungs. — The  influence  of  the  pneumogastric  upon  the  function 
of  the  lungs  is  exceedingly  important.  The  nerve  acts  here,  as  in 
most  other  organs  to  which  it  is  distributed,  in  a  double  or  mixed 
capacity ;  but  it  is  principally  as  the  sensitive  nerve  of  the  lungs 
that  it  has  thus  far  received  attention.  It  is  this  nerve  which 
conveys  from  the  lungs  to  the  medulla  oblongata  that  peculiar 
impression,  termed  besom  de  respirer,  which  excites  by  reflex  action 
the  diaphragm  and  intercostal  muscles,  and  keeps  up  the  play  of 
the  respiratory  movements.  As  we  have  already  shown,  this  action 
is  an  involuntary  one,  and  will  even  take  place  when  consciousness 
is  entirely  suspended.  It  may  indeed  be  arrested  for  a  time  by  an 
effort  of  the  will ;  but  the  impression  conveyed  to  the  medulla  soon 
becomes  so  strong,  and  the  stimulus  to  inspiration  so  urgent,  that 
they  can  no  longer  be  resisted,  and  the  muscles  contract  in  spite  of 
our  attempts  to  restrain  them. 

A  very  remarkable  effect  is  accordingly  produced  on  respiration 
by  simultaneous  division  of  both  pneumogastric  nerves.  This 
experiment  is  best  performed  on  adult  dogs,  which  may  be  ether- 
ized, and  the  nerves  exposed  while  the  animal  is  in  a  condition  of 
insensibility,  avoiding,  in  this  way,  the  disturbance  of  respiration, 
which  would  follow  if  the  dissection  were  performed  while  the  ani- 
mal was  conscious  and  sensible  to  pain.  After  the  effects  of  the 
etherization  have  entirely  passed  off,  and  respiration  and  circulation 
have  both  returned  to  a  quiescent  condition,  the  two  nerves,  which 
have  been  previously  exposed  and  secured  by  a  loose  ligature,  may 
be  instantaneously  divided,  and  the  effects  of  the  operation  readily 
appreciated. 

Immediately  after  the  division  of  the  nerves,  when  performed  in 
the  above  manner,  the  respiration  is  hurried  and  difficult,  owing  to 
the  sudden  paralysis  of  the  larynx  and  partial  closure  of  the  glottis 
by  the  vocal  chords,  as  already  described.  This  condition,  how- 
ever, is  of  short  continuance.  In  a  few  moments,  the  difficulty  of 
breathing  and  the  general  agitation  subside,  the  animal  becomes 
perfectly  quiet,  and  the  only  remaining  visible  effect  of  the  opera- 


PNEUMOGASTRIC    NERVE.  469 

tion  is  o  divfiinislied  frequency  in  the  movements  of  respiration.  This 
diminution  is  frequently  strongly  marked  from  the  first,  the  number 
of  respirations  tailing  at  once  to  ten  or  fifteen  per  minute,  and  be- 
coming, in  an  hour  or  two,  still  farther  reduced.  The  respirations 
are  performed  easily  and  quietly ;  and  the  animal,  if  left  undisturbed, 
remains  usually  crouched  in  a  corner,  without  giving  any  special 
signs  of  discomfort.  If  he  be  aroused  and  compelled  to  move 
about,  the  frequency  of  the  respiration  is  temporarily  augmented ; 
but  as  soon  as  he  is  again  quiet,  it  returns  to  its  former  standard. 
By  the  second  or  third  day,  the  number  of  respirations  is  often 
reduced  to  five,  four,  or  even  three  per  minute ;  when  this  is  the 
case,  the  animal  usually  appears  very  sluggish,  and  is  roused  with 
difiiculty  from  his  inactive  condition.  At  this  time  the  respiration 
is  not  only  diminished  in  frequency,  but  is  also  performed  in  a 
peculiar  manner.  The  movement  of  inspiration  is  slow,  easy,  and 
silent,  occupying  several  seconds  in  its  accomplishment ;  expiration, 
on  the  contrary,  is  sudden  and  audible,  and  is  accompanied  by  a  well 
marked  expulsive  effort,  which  has  the  appearance  of  being,  to  a 
certain  extent,  voluntary  in  character.  The  intercostal  spaces  also 
sink  inward  during  the  lifting  of  the  ribs ;  and  the  whole  movement 
of  respiration  has  an  appearance  of  insufficiency,  as  if  the  lungs 
were  not  thoroughly  filled  with  air.  This  insufficiency  of  respira- 
tion is  undoubtedly  owing  to  a  peculiar  alteration  in  the  pulmonary 
texture,  which  has  by  this  time  already  commenced. 

Death  takes  place  at  a  period  varying  from  one  to  six  days  after 
the  operation,  according  to  the  age  and  strength  of  the  animal. 
The  only  symptoms  accompanying  it  are  a  steady  failure  of  the 
respiration,  with  increased  sluggishness  and  indisposition  to  be 
aroused.  There  are  no  convulsions,  nor  any  evidences  of  pain. 
After  death  the  lungs  are  found  in  a  peculiar  state  of  solidification, 
which  is  almost  exclusively  a  consequence  of  this  operation,  and 
which  is  entirely  different  from  ordinary  inflammatory  hepatization. 
They  are  not  swollen,  but  rather  smaller  than  natural.  They  are 
of  a  dark  purple  color,  leathery  and  resisting  to  the  feel,  destitute 
of  crepitation,  and  infiltrated  with  blood.  Pieces  of  the  lung  cut 
out  sink  in  water.  The  pleural  surfaces,  at  the  same  time,  are  bright 
and  polished,  and  their  cavity  contains  no  effusion  or  exudation. 
The  lungs,  in  a  word,  are  simply  engorged  with  blood  and  empty 
of  air ;  their  tissue  having  undergone  no  other  alteration. 

These  changes  are  not  generally  uniform  over  both  lungs.  The 
organs  are  usually  mottled  on  their  exterior ;  the  variations  in  color 


470  THE    CRANIAL    NERVES. 

corresponding  with  the  different  degrees  of  alteration  exhibited  by 
different  parts. 

The  explanation  usually  adopted  of  the  above  consequences  fol- 
lowing division  of  the  pneumogastrics  is  as  follows :  The  nerves 
being  divided,  the  impression  which  originates  in  the  lungs  from 
the  accumulation  of  carbonic  acid,  and  which  is  destined  to  excite 
the  respiratory  movements  by  reflex  action,  can  no  longer  be  trans- 
mitted to  the  medulla  oblongata.  The  natural  stimulus  to  res;pira- 
tion  being  wanting,  it  is,  accordingly,  less  perfectly  performed.  The 
respiratory  movements  diminish  in  frequency,  and,  growing  con- 
tinually slower  and  slower,  finally  cease  altogether,  and  death  is 
the  result. 

The  above  explanation,  however,  is  not  altogether  sufficient.  It 
accounts  very  well  for  the  diminished  frequency  of  respiration,  but 
not  for  its  partial  continuance.  For  if  the  pneumogastric  nerves 
be  really  the  channel  through  which  the  stimulus  to  respiration  is 
conveyed  to  the  medulla,  the  difficulty  is  not  to  understand  why 
respiration  should  be  retarded  after  division  of  these  nerves,  but 
why  it  should  continue  at  all.  In  point  of  fact,  the  respiratory 
movements,  though  diminished  in  frequency,  continue  often  for 
some  days  after  this  operation.  This  cannot  be  owing  to  force  of 
habit,  or  to  any  remains  of  nervous  influence,  as  has  been  some- 
times suggested,  since,  when  the  medulla  itself  is  destroyed,  respira- 
tion, as  we  know,  stops  instantaneously,  and  no  attempt  at  move- 
ment is  made  after  the  action  of  the  nervous  centre  is  suspended. 

It  is  evident,  therefore,  that  the  pneumogastric  nerve,  though  the 
chief  agent  by  which  the  respiratory  stimulus  is  conveyed  to  the 
medulla,  is  not  the  only  one.  The  lungs  are  undoubtedly  the 
organs  which  are  most  sensitive  to  an  accumulation  of  carbonic 
acid,  and  an  imperfect  arterialization  of  the  blood ;  and  the  sensa- 
tion which  results  from  such  an  accumulation  is  accordingly  first 
felt  in  them.  There  is  reason  to  believe,  however,  that  all  the  vas- 
cular organs  are  more  or  less  capable  of  originating  this  impression, 
and  that  all  the  sensitive  nerves  are  capable,  to  some  extent,  of  trans- 
mitting it.  Although  the  first  disagreeable  sensation,  on  holding 
the  breath,  makes  itself  felt  in  the  lungs,  yet,  if  we  persist  in  sus- 
pending the  respiration,  we  soon  become  conscious  that  the  feeling 
of  discomfort  spreads  to  other  parts ;  and  at  last,  when  the  accu- 
mulation of  carbonic  acid  and  the  impurity  of  the  blood  have 
become  excessive,  all  parts  of  the  body  suffer  alike,  and  are  per- 
vaded by  a  general  feeling  of  derangement  and  distress.     It  is  easy, 


PXEL'MOGASTRIC    NERVE.  471 

tlierefore,  to  understand  why  respiration  should  be  retarded,  after 
section  of  the  pneumogastrics,  since  the  chief  source  of  the  stimulus 
to  resjjiration  is  cut  off;  but  the  movements  still  go  on,  though  more 
slowly  than  before,  because  the  other  sensitive  nerves,  which  con- 
tinue to  act,  are  also  capable,  in  an  imperfect  manner,  of  conveying 
the  same,  impression. 

The  immediate  cause  of  death,  after  this  operation,  is  no  doubt 
the  altered  condition  of  the  lungs.  These  organs  are  evidently 
very  imperfectly  filled  with  air,  for  some  time  previous  to  death ; 
and  their  condition,  as  shown  in  post-mortem  examination,  is  evi- 
dently incompatible  with  a  due  performance  of  the  respiratory 
function.  It  is  not  at  all  certain,  however,  that  these  alterations 
in  the  pulmonary  tissue  are  directly  dependent  on  division  of  the 
pneumogastric  nerves.  It  must  be  recollected  that  when  the  sec- 
tion of  the  pneumogastrics  is  performed  in  the  middle  of  the  neck, 
the  filaments  of  the  inferior  laryngeal  nerves  are  also  divided,  and 
the  narrowing  of  the  glottis,  produced  by  their  paralysis,  must 
necessarily  interfere  with  the  free  admission  of  air  into  the  chest. 
This  diflS-Culty,  either  alone  or  combined  Avith  the  diminished  fre- 
quency of  respiration,  must  have  a  very  considerable  effect  in  im- 
peding the  pulmonary  circulation,  and  bringing  the  lungs  into  such 
a  condition  as  unfits  them  for  maintaining  life. 

In  order  to  ascertain  the  comparative  influence  upon  the  lungs 
of  division  of  the  inferior  laryngeals  and  that  of  the  other  filaments 
of  the  pneumogastrics,  we  have  resorted  to  the  following  experi- 
ment. 

Two  pups  were  taken,  belonging  to  the  same  litter  and  of  the 
same  size  and  vigor,  about  two  weeks  old.  In  one  of  them  (No.  1) 
the  pneumogastrics  were  divided  in  the  middle  of  the  neck ;  and 
in  the  other  (No.  2)  a  section  was  made  at  the  same  time  of  the 
inferior  laryngeals,  the  trunk  of  the  pneumogastrics  being  left  un- 
touched. For  the  first  few  seconds  after  the  operation,  there  was 
but  little  difference  in  the  condition  of  the  two  animals.  There  was 
the  same  obstruction  of  the  breath  (owing  to  closure  of  the  glottis), 
the  same  gasping  and  sucking  inspiration,  and  the  same  frothing  at 
the  mouth.  Very  soou,  however,  in  pup  No.  1,  the  respiratory 
movements  became  quiescent,  and  at  the  same  time  much  reduced 
in  frequency,  falling  to  ten,  eight,  and  five  respirations  per  minute, 
as  usual  after  section  of  the  pneumogastrics ;  while  in  No.  2  the 
respiration  continued  frequent  as  well  as  laborious,  and  the  general 
signs  of  agitation  and  discomfort  were  kept  up  for  one  or  two  hours. 


472  THE    CRANIAL    NERVES. 

The  animal,  however,  after  that  time  became  exhausted,  cool,  and 
partially  insensible,  like  the  other.  They  both  died,  between  thirty 
and  forty  hours  after  the  operation.  On  post-mortem  inspection  it 
was  found  that  the  peculiar  congestion  and  solidification  of  the 
lungs,  considered  as  characteristic  of  division  of  the  pneumogastrics, 
existed  to  a  similar  extent  in  each  instance ;  and  the  only  appre- 
ciable difference  between  the  two  bodies  was  that  in  No.  1  the  blood 
was  coagulated,  and  the  abdominal  organs  natural,  while  in  No.  2 
the  blood  was  fluid  and  the  abdominal  organs  congested.  We  are 
led,  accordingly,  to  the  following  conclusions  with  regard  to  the 
effect  produced  by  division  of  this  nerve. 

1.  After  section  of  the  pneumogastrics,  death  takes  place  by  a  pecu- 
liar congestion  of  the  lungs. 

2.  This  congestion  is  not  directly  produced  by  division  of  the 
nerves,  but  is  caused  by  the  imperfect  admission  of  air  into  the 
chest. 

In  adult  dogs,  the  closure  of  the  glottis  from  paralysis  of  the 
laryngeal  muscles  is  less  complete  than  in  pups ;  but  it  is  still 
sufficient  to  exert  a  very  decided  influence  on  respiration,  and  to 
take  an  active  part  in  the  production  of  the  subsequent  morbid 
phenomena. 

"We  therefore  regard  the  death  which  takes  place  after  division 
of  both  pneumogastric  nerves,  as  produced  in  the  following  man- 
ner:— 

The  glottis  is  first  narrowed  by  paralysis  of  the  laryngeal  mus- 
cles, and  an  imperfect  supplj'-  of  air  is  consequently  admitted,  by 
each  inspiration,  into  the  trachea.  Next,  the  stimulus  to  respiration 
being  very  much  diminished,  the  respiratory  movements  take  place 
less  frequently  than  usual.  From  these  two  causes  combined,  the 
blood  is  imperfectly  arterialized.  But  the  usual  consequence  of 
such  a  condition,  viz.,  an  increased  rapidity  of  the  respiratory 
movements,  does  not  follow.  The  imperfect  arterialization  of 
the  blood  does  not  excite  the  respiratory  muscles  to  increased 
activity  as  it  would  do  in  health,  owing  to  the  division  of  the  pneu- 
mogastrics. At  the  same  time,  the  accumulation  of  carbonic  acid 
in  the  blood  and  in  the  tissues  begins  to  exert  a  narcotic  effect, 
diminishing  the  sensibility  of  the  nervous  centres,  and  tending  to 
retard  still  more  the  movements  of  respiration.  Thus  all  these 
causes  react  upon  and  aggravate  each  other ;  because  the  connec- 
tion, naturally  existing  between  imperfectly  arterialized  blood  and 
the  stimulus  to  respiration,  is  now  destroyed.     The  narcotism  and 


PNEUMOGASTKIC    NERVE.  473 

pulmonary  engorgement,  therefore,  continue  to  increase,  until  the 
lungs  are  so  seriously  altered  and  engorged  that  they  are  no  longer 
capable  of  transmitting  the  blood,  and  circulation  and  respiration 
come  to  an  end  at  the  same  time. 

It  must  be  remembered,  also,  that  the  pneumogastric  nerve  has 
other  important  distributions,  beside  those  to  the  larynx  and  the 
lungs;  and  the  eflect  produced  by  its  division  upon  these  other 
organs  has  no  doubt  a  certain  share  in  producing  the  results  which 
follow.  Bearing  in  mind  the  very  extensive  distribution  of  the 
pneumogastric  nerve  and  the  complicated  character  of  its  func- 
tions, we  may  conclude  that  after  section  of  this  nerve  death  takes 
place  from  a  combination  of  various  causes;  the  most  active  of 
which  is  a  peculiar  engorgement  of  the  lungs  and  imperfect  per- 
formance of  the  respiratory  function. 

Stomachj  and  Digestive  Function. — After  division  of  the  pneumo- 
gastric nerves,  the  sensations  of  hunger  and  thirst  remain,  and  the 
secretion  of  gastric  juice  continues.  Nevertheless  the  digestive 
function  is  disturbed  in  various  ways,  though  not  altogether  abo- 
lished. The  appetite  is  more  or  less  diminished,  as  it  would  be 
after  any  serious  operation,  but  it  remains  sufl&ciently  active  to 
show  that  its  existence  is  not  directly  dependent  on  the  integrity  of 
the  pneumogastric  nerve.  Digestion,  however,  very  seldom  takes 
place,  to  any  considerable  extent,  owing  to  the  following  circum- 
stances :  The  animal  is  frequently  seen  to  take  food  and  drink  with 
considerable  avidity ;  but  in  a  few  moments  afterward  the  food  and 
drink  are  suddenly  rejected  by  a  peculiar  kind  of  regurgitation. 
This  regurgitation  does  not  resemble  the  act  of  vomiting,  but  the 
substances  swallowed  are  again  discharged  so  easily  and  instan 
taneously  as  to  lead  to  the  belief  that  they  had  never  passed  into 
the  stomach.  Such,  indeed,  is  actually  the  case,  as  any  one  may 
convince  himself  by  watching  the  process,  which  is  often  repeated 
by  the  animal  at  short  intervals.  The  food  and  drink,  taken  volun- 
tarily, pass  down  into  the  oesophagus,  but  owing  to  the  paralysis  of 
the  muscular  fibres  of  this  canal,  are  not  conveyed  into  the  stomacK. 
They  accumulate  consequently  in  the  lower  and  middle  part  of  the 
oesophagus ;  and  in  a  few  moments  are  rejected  by  a  sudden  anti- 
staltic  action  of  the  parts,  excited,  apparently,  through  the  influence 
of  the  great  sympathetic. 

The  muscular  coat  of  the  stomach  is  also  paralyzed  to  a  con- 
siderable extent  by  section  of  this  nerve.  Longet  has  shown,  by 
introducing  food   artificially  into  the  stomach,  that  gastric  juice 


474  THE    CRANIAL    NERVES. 

may  be  secreted  and  the  food  be  actually  digested  and  disappear, 
■when  introduced  in  small  quantity.  But  when  introduced  in  large 
quantity,  it  remains  undigested,  and  is  found  after  death,  with  the 
exterior  of  the  mass  softened  and  permeated  by  gastric  juice,  while 
the  central  portions  are  unaltered,  and  do  not  even  seem  to  have 
come  in  contact  with  the  digestive  fluid.  This  is  undoubtedly 
owing  both  to  the  diminished  sensibility  of  the  mucous  membrane 
of  the  stomach,  and  to  the  paralysis  of  its  muscular  fibres.  The 
peristaltic  action  of  the  organ  is  very  important  in  digestion,  in 
order  to  bring  successive  portions  of  the  food  in  contact  with  its 
mucous  membrane,  and  to  carry  away  such  as  are  already  softened 
or  as  are  not  capable  of  being  digested  in  the  stomach.  This 
constant  movement  and  agitation  of  the  food  is  probably  also  one 
great  stimulus  to  the  continued  secretion  of  the  gastric  juice.  The 
digestive  fluid  will  therefore  be  deficient  in  quantity  after  division 
of  the  pneumogastric  nerve,  at  the  same  time  that  the  peristaltic 
movements  of  the  stomach  are  suspended.  Under  these  circum- 
stances, the  secretion  of  gastric  juice  may  be  sufficient  to  permeate 
and  digest  small  quantities  of  food,  while  a  larger  mass  may  resist 
its  action,  and  remain  undigested.  The  effect  produced  by  division 
of  these  nerves  on  the  digestive,  as  on  the  respiratory  organs,  is 
therefore  of  a  complicated  character,  and  results  from  the  combined 
action  of  several  different  causes,  which  influence  and  modify  each 
other. 

The  efiect  produced  upon  the  liver  by  section  of  the  pneumo- 
gastrics,  as  well  as  the  influence  usually  exerted  by  these  nerves 
upon  the  hepatic  functions,  has  been  so  little  studied  that  nothing 
definite  has  been  ascertained  in  regard  to  it.  "We  shall  therefore 
pass  over  this  portion  of  the  subject  in  silence. 

Spinal  Accessory. — This  nerve  originates,  by  many  filaments, 
from  the  side  of  the  medulla  oblongata,  below  the  level  of  the 
pneumogastric,  and  also  from  the  lateral  portions  of  the  spinal  cord, 
between  the  anterior  and  posterior  roots  of  the  upper  five  or  six 
cervical  nerves.  These  fibres  of  spinal  origin  pass  upward,  uniting 
into  a  slender  rounded  filament,  which  enters  the  cavity  of  the 
cranium  by  the  foramen  magnum,  and  is  then  joined  by  the  fibres 
which  originate  from  the  medulla  oblongata.  The  spinal  accessory 
nerve,  thus  constituted,  passes  out  from  the  cavity  of  the  skull  by 
the  posterior  foramen  lacerum,  in  company  with  the  glosso-pharyn- 
geal  and  pneumogastric  nerves.     Immediately  afterward  it  divides 


.    SPINAL    ACCESSORY.  475 

into  two  principal  branches:  First  the  internal  or  anastomotic 
branch,  which  joins  the  pneumogastric  nerve,  and  becomes  mingled 
with  its  fibres;  and,  secondly,  the  external  or  muscidar  branch, 
which  passes  downward  and  outward,  and  is  distributed  to  the 
sterno-mastoid  and  trapezius  muscles. 

The  spinal  accessory  is  essentially  a  motor  nerve.  It  has  been 
found,  both  by  Bernard  and  Longet,  to  be  insensible  at  its  origin, 
like  the  anterior  roots  of  the  spinal  nerves ;  but  if  irritated  after 
its  exit  from  the  skull,  it  gives  signs  of  sensibility.  This  sensibi- 
lity it  acquires  from  the  filaments  of  inosculation  which  it  receives 
from  the  anterior  branches  of  the  first  and  second  cervical  nerves. 
Though  its  external  branch,  accordingly,  is  exclusively  distributed 
to  muscles,  as  we  have  already  seen,  this  branch  contains  some  sensi- 
tive fibres,  which  have  the  same  destination.  The  reason  for  this 
anatomical  fact,  viz.,  that  motor  nerves  are  supplied  during  their 
course  with  sensitive  fibres,  becomes  evident  when  we  reflect  that  the 
muscles  themselves  possess  a  certain  degree  of  sensibility,  though 
less  acute  than  that  which  belongs  to  the  skin.  The  sensibility  of 
the  muscles  is  undoubtedly  essential  to  the  perfect  performance  of 
their  function ;  and  as  the  motor  nerves  are  incapable,  by  them- 
selves, of  transmitting  sensitive  impressions,  they  are  joined,  soon 
after  their  origin,  by  other  filaments  which  communicate  to  them 
this  necessary  power. 

The  most  important  result  which  has  been  obtained  by  experi- 
ment upon  the  spinal  accessory  nerve,  is  that  its  internal  or  anasto- 
motic branch  is  directly  connected  with  the  vocal  movements  of  the 
glottis.  It  has  been  found  by  Bischoflf,  by  Longet,  and  by  Bernard, 
that  if  the  spinal  accessory  nerves  on  both  sides,  or  their  branches 
of  inosculation  with  the  pneumogastric,  be  divided  or  lacerated, 
the  pneumogastric  nerves  themselves  being  left  entire,  the  voice  is 
instantly  lost,  and  the  animal  becomes  incapable  of  making  a  vocal 
sound.  We  have  also  found  this  result  to  follow,  in  the  cat,  after 
the  spinal  accessory  nerves  have  been  torn  out  by  their  roots, 
through  the  jugular  foramen.  The  animal,  after  this  operation,  can 
no  longer  make  an  audible  sound.  At  the  same  time  the  respira- 
tory movements  of  the  glottis  go  on  undisturbed,  and  most  of  the 
other  animal  functions  remain  unaffected. 

The  fibres  of  communication,  therefore,  derived  from  the  spinal 
accessory,  pass  to  the  pneumogastric  nerve  and  become  entangled 
with  its  other  filaments,  so  that  they  can  no  longer  be  traced  by 
anatomical  dissection.     They  pass  downward,  however,  and  become 


476  THE    CRANIAL    NERVES. 

a  part  of  the  motor  fibres  of  the  inferior  laryngeal  or  recurrent 
branches  of  the  pneumogastric ;  being  finally  distributed  to  the 
muscles  of  the  larynx,  which  they  supply  with  those  nervous  influ- 
ences which  are  required  for  the  formation  of  the  voice. 

The  special  function  of  the  external  or  muscular  branch  of  the 
spinal  accessory  is  not  so  fully  understood.  This  branch,  as  we 
have  seen,  is  distributed  to  the  sterno- mastoid  and  trapezius  mus- 
cles. But  these  muscles  also  receive  filaments  from  the  cervical 
spinal  nerves ;  and,  accordingly,  they  still  retain  the  power  of  mo- 
tion, to  a  certain  degree,  after  the  external  branches  of  the  spinal 
accessory  have  been  divided  on  both  sides. 

The  spinal  accessory  is,  accordingly,  a  nerve  of  very  peculiar 
distribution.  For  it  partly  supplies  motor  fibres  to  the  pneumo- 
gastric nerve,  and  is  partly  distributed  to  two  muscles,  both  of 
which  also  receive  motor  nerves  from  another  source.  Sir  Charles 
Bell,  noticing  the  close  connection  between  this  nerve  and  the 
pneumogastric,  regarded  the  two  as  associated  also  in  their  func- 
tion, as  nerves  of  respiration.  He  considered,  therefore,  the  exter- 
nal branch  of  the  spinal  accessory  as  destined  to  assist  in  the 
movements  of  respiration,  when  these  movements  become  unusu- 
ally laborious,  by  bringing  into  play  the  sterno-mastoid  and  trape- 
zius muscles,  in  aid  of  the  action  of  the  intercostals.  He  therefore 
called  this  nerve  the  "  superior  respiratory  nerve," 

But  the  most  satisfactory  explanation  of  this  peculiarity  is  that 
proposed  by  M,  Bernard.  According  to  this  explanation,  whenever 
a  muscle,  or  set  of  muscles,  derive  their  nervous  influence  from  two 
different  sources,  this  is  not  for  the  purpose  of  assisting  them  in  the 
performance  of  the  same  function,  but  of  enabling  them  to  perform 
two  different  functions.  We  have  seen  this  already  exemplified  in 
the  muscles  of  the  larynx.  For  these  muscles  perform  certain 
movements  of  respiration  for  which  they  receive  indirectly  filaments 
from  the  facial  hypoglossal,  and  cervical  nerves.  But  they  also 
perform  the  movements  necessary  to  the  formation  of  the  voice,  the 
nervous  stimulus  for  which  is  derived  altogether  from  the  spinal 
accessory. 

The  internal  branch  of  the  spinal  accessory,  accordingly,  excites, 
in  the  parts  to  which  it  is  distributed  a  function  which  is  incompa- 
tible with  respiration.  For  the  movements  of  respiration  cannot 
go  on  while  the  voice  is  sounded;  and  a  necessary  preliminary 
to  the  production  of  a  vocal  sound,  is  the  temporary  stoppage  of 
respiration.     The   movements   of  respiration,   therefore,  and   the 


HYPOGLOSSAL.  477 

movements  of  the  voice  alternate  with  each  other,  but  are  never 
simultaneous ;  so  that  the  internal  branch  of  the  spinal  accessory  is 
antagonistic  to  the  motor  fibres  of  the  larynx  derived  from  other 
nerves. 

It  is  thought  by  M.  Bernard,  that  the  fibres  of  the  external 
branch  of  the  spinal  accessory  have  also  a  function  which  is  anta- 
gonistic to  respiration.  For  respiration  is  naturally  suspended  in 
all  steady  and  prolonged  muscular  efforts.  In  these  efforts,  such  as 
those  of  straining,  lifting,  and  the  like,  the  movements  of  respira- 
tion cease,  the  spinal  column  is  made  rigid  by  the  contraction  of 
its  muscles,  and  the  head  and  neck  are  placed  in  a  fixed  position, 
principally  by  the  contraction  of  the  sterno-mastoid  and  trapezius 
muscles.  The  function  of  the  spinal  accessory,  in  both  its  branches, 
is  therefore  regarded  as  destined  to  excite  movements  which  are 
incompatible  with  those  of  respiration ;  and  which  accordingly  come 
into  play  only  when  the  ordinary  movements  of  respiration  have 
been  temporarily  suspended. 

Hypoglossal. — The  hypoglossal  nerve  originates  from  the  ante- 
rior and  lateral  portions  of  the  medulla  oblongata,  and  passing  out 
by  the  anterior  condyloid  foramen,  is  distributed  exclusively  to  the 
muscles  of  the  tongue.  Irritation  of  its  fibres  in  any  part  of  their 
course  produces  convulsive  twitching  in  this  organ.  Its  section 
paralyzes  completely  the  movements  of  the  tongue,  without  affect- 
ing directly  the  sensibility  of  its  mucous  membrane.  This  nerve, 
accordingly,  is  the  motor  nerve  of  the  tongue.  If  irritated  at  its 
origin,  the  hypoglossal  nerve,  according  to  the  experiments  of 
Longet,  is  entirely  insensible ;  but  if  the  irritation  be  applied  in  the 
middle  of  its  course,  signs  of  pain  are  immediately  manifested.  Its 
sensibility,  like  that  of  the  facial,  is  consequently  derived  from  its 
inosculation  with  other  sensitive  nerves,  after  its  emergence  from 
the  skull. 


478  THE    SPECIAL    SENSES. 


CHAPTER    VI. 

THE  SPECIAL   SENSES. 

Geneeal  and  Special  Sensibility. — We  have  already  seen 
that  there  exists,  in  the  general  integument,  a  power  of  sensation,  by 
which  we  are  made  acquainted  with  surrounding  objects  and  some 
of  their  most  important  physical  qualities.  By  this  power  we  feel 
the  sensations  of  heat  and  cold,  and  are  enabled  to  distinguish 
between  hard  and  soft  substances,  rough  bodies  and  smooth,  solids 
and  liquids.  This  kind  of  power  is  termed  General  Sensibility, 
because  it  resides  in  the  general  integument,  and  because  by  its 
aid  we  obtain  information  with  regard  to  the  simplest  and  most 
material  properties  of  external  objects. 

The  general  sensibility,  thus  existing  in  the  integument,  is  an 
endowment  of  the  sensitive  nerves  derived  from  the  cerebro-spinal 
system.  These  nerves  ramify  in  the  substance  of  the  skin,  and  by 
subsequent  inosculation  form  a  minute  plexus  in  the  superficial 
portions  of  the  tissue  of  the  corium.  From  this  plexus,  the  ulti- 
mate filaments,  reduced  to  an  exceedingly  minute  size,  pass  up- 
ward into  the  conical  papillse  with  which  the  free  surface  of  the 
corium  is  covered.  In  the  papillae  the  nervous  filaments  terminate, 
sometimes  by  loops  returning  upon  themselves,  and  sometimes  ap- 
parently by  free  extremities.  The  papillae  are  also  supplied  with 
looped  capillary  bloodvessels,  and  are  capable  of  receiving  an 
abundant  vascular  injection. 

These  papillae  appear  to  be  the  most  essential  organs  of  general 
sensation,  since  the  sensibility  of  the  skin  is  most  acute  where  they 
are  most  abundant  and  most  highly  developed,  as,  for  example,  on 
the  palm  of  the  hand  and  the  tips  of  the  fingers. 

The  best  method  of  measuring  accurately  the  sensibility  of  dif- 
ferent regions  is  that  adopted  by  Professors  Weber  and  Valentin. 
They  applied  the  rounded  points  of  a  pair  of  compasses  to  the 
integument  of  different  parts,  and  found  that  if  they  were  held 
very  near  together  they  could  no  longer  be  distinguished  as  sepa- 


GENERAL    AND    SPECIAL    SENSIBILITY.       ^  479 

rate  points,  but  the  two  sensations  were  confounded  into  one.  The 
distance,  however,  at  which  the  two  points  failed  to  be  distinguished 
from  each  other,  was  much  shorter  for  some  parts  of  the  body 
than  for  others.  Prof.  Valentin's  measurements,^  which  are  the 
most  varied  and  complete,  give  the  following'as  the  limits  of  dis- 
tinct perception  in  various  parts : — 

Paris  Line. 

At  the  tip  of  tongue .483 

"  palmar  surface  of  tips  of  fingers       ....  .723 

"            "         "         of  second  phalanges         .         .         .  1.558 

"            "        "         of  first  phalanges     .         .         .         .  1.650 

"  dorsum  of  tongue 2.500 

"  dorsal  surface  of  fingers  ......  3.900 

"  cheek 4.541 

"  back  of  hand 6.966 

"  skin  of  throat 8.292 

"  dorsum  of  foot 12.525 

•'  skin  over  sternum  .         .         .         .         .         .         .  15.875 

"  middle  of  back        .        .        .        .        .        .        .  24.208 

This  method  cannot,  of  course,  give  the  absolute  measure  of  the 
acuteness  of  sensibility  in  the  different  regions,  since  the  two-  points 
might  be  less  easily  distinguished  from  each  other  in  any  one  re- 
gion, and  yet  the  absolute  amount  of  sensation  produced  might  be 
as  great  as  in  the  surrounding  parts ;  still  it  is  undoubtedly  a  very 
accurate  measure  of  the  delicacy  of  tactile  sensation,  by  which  we 
are  enabled  to  distinguish  slight  inequalities  in  the  surface  of  solid 
bodies.  We  find,  furthermore,  that  certain  parts  of  the  body  are 
particularly  well  adapted  to  exercise  the  function  of  general  sen- 
sation, not  only  on  account  of  the  acute  sensibility  of  their  integu- 
ment, but  also  owing  to  their  peculiar  formation.  Thus,  in  man, 
the  hands  are  especially  well  formed  in  this  respect,  owing  to  the 
articulation  and  mobility  of  the  fingers,  by  which  they  may  be 
adapted  to  the  surface  of  solid  bodies,  and  brought  successively 
in  contact  with  all  their  irregularities  and  depressions.  The  hands 
are  therefore  more  especially  used  as  organs  of  touch,  and  we  are 
thus  enabled  to  obtain  by  their  aid  the  most  delicate  and  precise 
information  as  to  the  texture,  consistency,  configuration,  &c.,  of 
foreign  bodies. 

But  the  hands  are  not  the  exclusive  organs  of  touch,  even  in  the 
human  subject,  and  in  some  of  the  lower  animals,  the  same  func- 

'  In  Todd's  Cyclopadia  of  Anatomy  and  Physiology,  vol.  iv.,  article  on  Touch, 
by  Dr.  Carpenter. 


480  _  THE    SPECIAL    SENSES. 

tion  is  fuUj  performed  by  various  other  parts  of  the  body.  Thus 
in  the  cat  and  in  the  seal,  the  long  bristles  seated  upon  the  lips  are 
■used  for  this  purpose,  each  bristle  being  connected  at  its  base  with 
a  highly  developed  nervous  papilla :  in  some  of  the  monkeys  the 
extremity  of  the  prehensile  tail,  and  in  the  elephant  the  end  of  the 
nose,  which  is  developed  into  a  flexible  and  sensitive  proboscis,  is 
employed  as  an  organ  of  touch.  This  function,  therefore,  may  be 
performed  by  either  one  part  of  the  body  or  another,  provided  the 
accessory  organs  be  developed  in  a  favorable  manner. 

About  the  head  and  face,  the  sensibility  of  the  skin  is  dependent 
mainly  upon  branches  of  the  fifth  pair.  In  the  neck,  trunk,  and 
extremities  it  is  due  to  the  sensitive  fibres  of  the  cervical,  dorsal, 
and  lumbar  spinal  nerves.  It  exists  also,  to  a  considerable  extent, 
in  the  mucous  membranes  of  the  mouth  and  nose,  and  of  the  pas- 
sages leading  from  them  to  the  interior  of  the  body.  In  these 
situations,  it  depends  upon  the  sensitive  filaments  of  certain  of  the 
cranial  nerves,  viz.,  the  fifth  pair,  the  glosso-pharyngeal,  and  the 
pneumogastric.  The  sensibility  of  the  mucous  membranes  is  most 
acute  in  those  parts  supplied  by  branches  of  the  fifth  pair,  viz.,  the 
conjunctiva,  anterior  part  of  the  nares,  inside  of  the  lips  and  cheeks, 
and  the  anterior  two-thirds  of  the  tongue.  At  the  base  of  the 
tongue  and  in  the  fauces,  where  the  mucous  membrane  is  supplied 
by  filaments  of  the  glosso-pharyngeal  nerve,  the  general  sensibility 
is  less  perfect;  and  finally  it  diminishes  rapidly  from  the  upper 
part  of  the  oesophagus  and  the  glottis  toward  the  stomach  and  the 
lungs.  Thus,  we  can  appreciate  the  temperature  and  consistency 
of  a  foreign  substance  very  readily  in  the  mouth  and  fauces,  but 
these  qualities  are  less  distinctly  perceived  in  the  oesophagus,  and 
not  at  all  in  the  stomach,  unless  the  foreign  body  happen  to  be 
excessively  hot  or  cold,  or  unusually  hard  and  angular  in  shape. 
The  general  sensibility,  which  is  resident  in  the  skin  and  in  a  certain 
portion  of  the  mucous  membranes,  diminishes  in  degree  from  with- 
out inward,  and  disappears  altogether  in  those  organs  which  are 
not  supplied  with  nerves  from  the  cerebro-spinal  system. 

It  is  particularly  to  be  observed,  however,  that  while  the  general 
sensibility  of  the  skin,  and  of  the  mucous  membranes  above  men- 
tioned, varies  in  acuteness  in  different  parts  of  the  body,  it  is  every- 
where the  same  in  kind.  The  tactile  sensations,  produced  by  the 
contact  of  a  foreign  body,  are  of  precisely  the  same  nature  whether 
they  be  felt  by  the  tips  of  the  fingers,  the  dorsal  or  palmar  surfaces 
of  the  hands,  the  lips,  cheeks,  or  any  other  part  of  the  integument. 


TASTE.  4.81 

The  only  difference  in  the  sensibility  of  these  parts  lies  in  the  de- 
gree of  its  development. 

But  there  are  certain  other  sensations  which  are  different  in  kind 
from  those  perceived  by  the  general  integument,  and  which,  owing 
to  their  peculiar  and  special  character,  are  termed  special  sensations. 
Such  are,  for  example,  the  sensation  of  light,  the  sensation  of  sound,, 
the  sensation  of  savor,  and  the  sensation  of  odors.  The  special 
sensibility  which  enables  us  to  feel  the  impressions  derived  from 
these  sources  is  not  distributed  over  the  body,  like  ordinary  sensi- 
bility, but  is  localized  in  distinct  organs,  each  of  which  is  so  con- 
stituted as  to  receive  the  special  sensation  peculiar  to  it,  and  no 
other. 

Thus  we  have,  beside  the  general  sensibility  of  the  skin  and 
mucous  membranes,  certain  peculiar  faculties  or  special  sevtses,  as 
they  are  called,  which  enable  us  to  derive  information  from  ex- 
ternal objects,  which  we  could  not  possibly  obtain  by  any  other 
means.  Thus  light,  however  intense,  produces  no  perceptible  sen- 
sation when  allowed  to  fall  upon  the  skin,  but  only  when  admitted 
to  the  eye.  The  sensation  of  sound  is  perceptible  only  by  the 
ear,  and  that  of  odors  only  by  the  olfactory  membrane.  These 
different  sensations,  therefore,  are  not  merely  exaggerations  of 
ordinary  sensibility,  but  are  each  distinct  and  peculiar  in  their 
nature,  and  are  in  relation  with  distinct  properties  of  external 
objects. 

In  examining  the  organs  of  special  sense,  we  shall  find  that  they 
each  consist — First,  of  a  nerve,  endowed  with  the  special  sensibility 
required  for  the  exercise  of  its  peculiar  function  ;  and.  Secondly,  of 
certain  accessory  parts,  forming  an  apparatus  more  or  less  compli- 
cated, which  is  intended  to  assist  in  its  performance  and  render  it 
more  delicate  and  complete.  We  shall  take  up  the  consideration 
of  the  special  senses  in  the  following  order.  First,  the  sense  of 
Taste ;  second,  that  of  Smell ;  third,  that  of  Sight ;  and  fourth,  that 
of  Hearing. 

Taste. — We  begin  the  study  of  the  special  senses  with  that  of 
Taste,  because  this  sense  is  less  peculiar  than  any  of  the  others,  and 
differs  less,  both  in  its  nature  and  its  conditions,  from  the  ordinary 
sensiVnlity  of  the  skin.  In  the  first  place,  the  organ  of  taste  is  no 
other  than  a  portion  of  the  mucous  membrane,  beset  with  vascular 
and  nervous  papilla;,  similar  to  those  of  the  general  integument. 
31 


482  THE    SPECIAL    SENSES. 

Secondly,  it  gives  us  impressions  of  such  substances  only  as  are 
actually  in  contact  with  sensitive  surfaces,  and  can  establish  no 
communication  with  objects  at  a  distance.  Thirdly,  the  surfaces 
which  exercise  the  sense  of  taste  are  also  endowed  with  general  sen- 
sibility; and  Fourthly,  there  is  no  one  special  and  distinct  nerve 
of  taste,  but  this  property  resides  in  portions  of  two  different 
nerves,  viz.,  the  fifth  pair  and  the  glosso-pharyngeal ;  nerves  which 
also  supply  general  sensibility  to  the  mouth  and  surrounding  parts. 

The  sense  of  taste  is  localized  in  the  mucous  membrane  of  the 
tongue,  the  soft  palate,  and  the  fauces.  The  tongue,  which  is  more 
particularly  the  seat  of  this  sense,  is  a  flattened,  leaf-like,  muscular 
organ,  attached  to  the  inner  surface  of  the  symphysis  of  the  lower 
jaw  in  front,  and  to  the  os  hyoides  behind.  It  has  a  vertical  sheet 
or  lamina  of  fibrous  tissue  in  the  median  line,  which  serves  as  a 
framework,  and  is  provided  with  an  abundance  of  longitudinal 
transverse  and  radiating  muscular  fibres,  by  which  it  can  be  elon- 
gated, retracted,  and  moved  about  in  every  direction. 

The  mucous  membrane  of  the  fauces  and  posterior  third  of  the 
tongue,  like  that  lining  the  cavity  of  the  mouth,  is  covered  with 
minute  vascular  papillae,  similar  to  those  of  the  skin,  which  are, 
however,  imbedded  and  concealed  in  the  smooth  layer  of  epithe- 
lium forming  the  surface  of  the  organ.  But  about  the  junction  of 
its  posterior  and  middle  thirds,  there  is,  upon  the  dorsum  of  the 
tongue,  a  double  row  of  rounded  eminences,  arranged  in  a  V-shaped 
figure,  running  forward  and  outward,  on  each  side,  from  the  situa- 
tion of  the  foramen  csecum  ;  and,  from  this  point  forward,  the  upper 
surface  of  the  organ  is  everywhere  covered  with  an  abundance  of 
thickly-set,  highly  developed  papillae,  projecting  from  its  surface, 
and  readily  visible  to  the  naked  eye. 

These  lingual  papillas  are  naturally  divided  into  three  different 
sets  or  kinds.  First,  the  filiform  papillse,  which  are  the  most  nume- 
rous, and  which  cover  most  uniformly  the  upper  surface  of  the 
organ.  They  are  long  and  slender,  and  are  covered  with  a  some- 
what horny  epithelium,  usuallj^  prolonged  at  their  free  extremity 
into  a  filamentous  tuft.  At  the  edges  of  the  tongue  these  papillae 
are  often  united  into  parallel  ranges  or  ridges  of  the  mucous  mem- 
brane. Secondly,  the  fungiform  papillse.  These  are  thicker  and 
larger  than  the  others,  of  a  rounded  club-shaped  figure,  and  covered 
with  soft,  permeable  epithelium.  They  are  most  abundant  at  the 
tip  of  the  tongue,  but  may  be  seen  elsewhere  on  the  surface  of  the 
organ,  scattered  among  the  filiform  papillse.     Thirdly,  the  circum- 


TASTE. 


483 


vallate  papillse.  These  are  the  rounded  eminences  which  form  the 
V-shaped  figure  near  the  situation  of  the  foramen  caecum.  They 
are  eight  or  ten  in  number.  Each  one  of  them  is  surrounded  bj 
a  circular  wall,  or  circumvallation,  of  mucous  membrane,  which 
gives  to  them  their  distinguishing  appellation.  The  circumvalla- 
tion, as  well  as  the  central  eminence,  has  a  structure  similar  to  that 
of  the  fungiform  papillae. 

The  sensitive  nerves  of  the  tongue,  as  we  have  already  seen,  are 
two  in  number,  viz.,  the  lingual  branch  of  the  fifth  pair,  and  the 
lingual  portion  of  the  glosso-pharyngeal.  The  lingual  branch  of 
the  fifth  pair  enters  the  tongue  at  the  anterior  border  of  the  hyo- 
glossus  muscle,  and  its  fibres  then  run  through  the  muscular  tissue 
of  the  organ,  from  below  upward  and  from  behind  forward,  with- 
out any  ultimate  distribution,  until  they  reach  the  mucous  mem- 
brane. The  nervous  filaments  then  penetrate  into  the  lingual 
papillae,  where  they  finally  terminate.  The  exact  mode  of  their 
termination  is  not  positively  known.  According  to  Kolliker,  they 
sometimes  seem  to  end  in  loops,  and  sometimes  by  free  extremities. 

The  lingual  portion  of  the  glosso-pharyngeal  nerve  passes  into 
the  tongue  below  the  posterior  border  of  the  hyo-glossus  muscle. 
It  then  divides  into  various  branches,  which  pass  through  the  mus- 
cular tissue,  and  are  finally  distributed  to  the  raucous  membrane  of 
the  base  and  sides  of  the  organ. 

Fig.  153. 


BiAORAM  OF  ToNooE,  With  its  »ea»iti  ve  nerves  aod  papUlaj. — 1.  Lingual  branch  of  fifth  pair, 
2.  Glosso-pharyngeal  nerve. 


The  mucous  membrane  of  the  base  of  the  tongue,  of  its  edges, 
and  its  under  surface  near  the  tip,  as  well  as  the  mucous  membrane 
of  the  mouth  and  fauces  generally,  is  also  supplied  with  mucous 
follicles,  which  furnish  a  viscid  secretion  by  which  the  free  surface 
of  the  parts  is  luVjricated. 


484:  THE    SPECIAL    SENSES. 

Finally,  the  muscles  of  the  tongue,  it  will  be  remembered,  are 
animated  exclusively  by  the  filaments  of  the  hypoglossal  nerve. 

The  exact  seat  of  the  sense  of  taste  has  been  determined  by 
placing  in  contact  with  different  parts  of  the  mucous  membrane  a 
small  sponge,  moistened  with  a  solution  of  some  sweet  or  bitter 
substance.  The  experiments  of  Verniere,  Longet  and  others  have 
shown  that  the  sense  of  taste  resides  in  the  whole  superior  surface, 
the  point  and  edges  of  the  tongue,  the  soft  palate,  fauces,  and  part 
of  the  pharynx.  The  base,  tip,  and,  edges  of  the  tongue  seem  to 
possess  the  most  acute  sensibility  to  savors,  the  middle  portion  of 
its  dorsum  less  of  this  sensibility,  and  its  inferior  surfaces  little  or 
none.  Now  as  the  whole  anterior  part  of  the  organ  is  supplied  by 
the  lingual  branch  of  the  fifth  pair  alone,  and  the  whole  of  its 
posterior  portion  by  the  glosso-pharyngeal,  it  follows  that  the  sense 
of  taste,  in  these  different  parts,  is  derived  from  these  two  different 
nerves. 

Furthermore,  the  tongue  is  supplied,  at  the  same  time  and  hy  the 
same  nerves,  with  general  sensibility  and  with  the  special  sensibility  of 
taste.  The  general  sensibility  of  the  anterior  portion  of  the  tongue, 
and  that  of  the  branch  of  the  fifth  pair  with  which  it  is  supplied, 
are  sufficiently  well  known.  Section  of  the  fifth  pair  destroys  the 
sensibility  of  this  part  of  the  tongue  as  well  as  that  of  the  rest  of 
the  face.  Longet  has  found  that  after  the  lingual  branch  of  this 
nerve  has  been  divided,  the  mucous  membrane  of  the  anterior  two- 
thirds  of  the  tongue  may  be  cauterized  with  a  hot  iron  or  with 
caustic  potassa,  in  the  living  animal,  without  producing  any  sign  of 
pain.  Dr.  John  Eeid,  on  the  other  hand,  together  with  other  experi- 
menters, has  determined  that  ordinary  sensibility  exists  in  a  marked 
degree  in  the  glosso-pharyngeal,  and  is  supplied  by  it  to  the  parts 
to  which  this  nerve  is  distributed. 

Accordingly  we  must  distinguish,  in  the  impressions  produced 
by  foreign  substances  taken  into  the  mouth,  between  the  special 
impressions  derived  from  their  sapid  qualities,  and  the  general  sensa- 
tions produced  by  their  ordinary  physical  properties.  As  the  tongue  is 
exceedingly  sensitive  to  ordinary  impressions,  and  as  the  same  body 
is  often  capable  of  exciting  both  the  tactile  and  gustatory  functions, 
these  two  properties  are  sometimes  liable  to  be  confounded  with 
each  other  by  careless  observation.  The  truly  sapid  qualities, 
however,  the  only  ones,  properly  speaking,  which  we  perceive  by 
the  sense  of  taste,  are  such  savors  as  we  designate  by  the  term 
sweet,  bitter,  salt,  sour,  alkaline,  and  the  like.     But  there  are  many 


TASTE.  485 

otlier  properties,  belonging  to  various  articles  of  food,  which,  belong 
really  to  the  class  of  ordinary  physical  qualities  and  are  appre- 
ciated by  the  ordinary  sensibility  of  the  tongue,  though  we  usually 
speak  of  them  as  being  perceived  by  the  taste.  Thus  a  starchy, 
viscid,  watery,  or  oleaginous  taste  is  merely  a  certain  variety  of  con- 
sistency in  the  substance  tasted,  which  may  exist  either  alone  or  in 
connection  with  real  savors,  but  which  is  exclusively  perceived  by 
means  of  the  general  sensibility.  So  also  with  a  jmngent  or  hurning 
taste,  such  as  that  of  red  pepper  or  any  other  irritating  powder. 
The  quality  of  piquancy  in  the  preparation  of  artificial  kinds  of 
food  is  always  communicated  to  them  by  the  addition  of  some  such 
irritating  substance.  The  styptic  taste  seems  to  be  a  combination  of 
an  ordinary  irritant  or  astringent  effect  with  a  peculiar  taste,  which 
we  always  associate  with  the  former  quality  in  astringent  sub- 
stances. 

There  is  also  sometimes  a  liability  to  confound  the  real  taste  of 
certain  substances  with  their  odorous  properties,  or  flavors.  Thus 
in  most  aromatic  articles  of  food,  such  as  tea  and  coffee,  and  in 
various  kinds  of  wine,  a  great  part  of  what  we  call  the  taste  is  in 
reality  due  to  the  aroma,  or  smell  which  reaches  the  nares  during 
the  act  of  swallowing.  Even  in  many  solid  kinds  of  food,  such  as 
freshly  cooked  meats,  the  odor  produces  a  very  important  part  of 
their  effect  on  the  senses.  We  can  easily  convince  ourselves  of  this 
by  holding  the  nose  while  swallowing  such  substances,  or  by  recol- 
lecting how  much  a  common  catarrh  interferes  with  our  perception 
of  their  taste. 

The  most  important  conditions  of  the  sense  of  taste  are  the  fol- 
lowing : — 

In  the  first  place,  the  sapid  substance,  in  order  that  its  taste  may 
be  perceived,  must  be  brought  in  contact  with  the  mucous  mem- 
brane of  the  mouth  in  a  state  of  solution.  So  long  as  it  remains 
solid,  however  marked  a  savor  it  may  possess,  it  gives  no  other 
impression  than  that  of  any  foreign  body  in  contact  with  the  sensi- 
tive surfaces.  But  if  it  be  applied  in  a  liquid  form,  it  is  then  spread 
over  the  surface  of  the  mucous  membrane,  and  its  taste  is  imme- 
diately perceived.  Thus  it  is  only  the  liquid  and  soluble  portions 
of  our  food  which  are  tasted,  such  as  the  animal  and  vegetable 
juices  and  the  soluble  salts.  Saline  substances  which  are  insoluble, 
such  as  calomel  or  carbonate  of  lead,  when  applied  to  the  tongue, 
produce  no  gustatory  sensation  whatever. 

The  mechanism  of  the  sense  of  taste  is,  therefore,  in  all  proba- 


486  THE    SPECIAL    SENSES. 

bilitj,  a  direct  and  simple  one.  The  sapid  substances  in  solution 
penetrate  the  lingual  papillae  by  endosmosis,  and,  coming  in  actual 
contact  with  the  terminal  nervous  filaments,  excite  their  sensibility 
by  uniting  with  their  substance.  We  have  already  seen  that  the 
rapidity  with  which  endosmosis  will  take  place  under  certain  con- 
ditions is  sufficiently  great  to  account  for  the  almost  instantaneous 
perception  of  the  taste  of  sapid  substances  when  introduced  into  the 
mouth. 

It  is  on  this  account  that  a  free  secretion  of  the  salivary  fluids  is 
so  essential  to  the  full  performance  of  the  gustatory  function.  If 
the  mouth  be  dry  and  parched,  our  food  seems  to  have  lost  its  taste ; 
but  when  the  saliva  is  freely  secreted,  it  is  readily  mixed  with  the 
food  in  mastication,  and  assists  in  the  solution  of  its  sapid  ingredi- 
ents ;  and  the  fluids  of  the  mouth,  thus  impregnated  with  the  savory 
substances,  are  absorbed  by  the  mucous  membrane,  and  excite  the 
gustatory  nerves.  An  important  part,  also,  is  taken  in  this  process 
by  the  movements  of  the  tongue ;  for  by  these  movements  the  food 
is  carried  from  one  part  of  the  mouth  to  another,  pressed  against 
the  hard  palate,  the  gums,  and  the  cheeks,  its  solution  assisted,  and 
the  penetration  of  the  fluids  into  the  substance  of  the  papillse  more 
rapidly  accomplished.  If  a  little  powdered  sugar,  or  some  vege- 
table extract  be  simply  placed  upon  the  dorsum  of  the  tongue,  but 
little  eSect  is  produced ;  but  as  soon  as  it  is  pressed  by  the  tongue 
against  the  roof  of  the  mouth,  as  naturally  happens  in  eating  or 
drinking,  its  taste  is  immediately  perceived.  This  effect  is  easily 
explained ;  since  we  know  how  readily  movement  over  a  free  sur- 
face, combined  with  slight  friction,  will  facilitate  the  imbibition  of 
liquid  substances.  The  nervous  papillae  of  the  tongue  may  there- 
fore be  regarded  as  the  essential  organs  of  the  sense  of  taste,  and 
the  lingual  muscles  as  its  accessory  organs. 

The  full  effect  of  sapid  substances  is  not  obtained  until  they  are  actu- 
ally swallowed.  During  the  preliminary  process  of  mastication  a 
sufficient  degree  of  impression  is  produced  to  enable  us  to  perceive 
the  presence  of  any  disagreeable  or  injurious  ingredient  in  the  food, 
and  to  get  rid  of  it,  if  we  desire.  But  it  is  only  when  the  food  is 
carried  backward  into  the  fauces  and  pharynx,  and  is  compressed 
by  the  constrictor  muscles  of  these  parts,  that  we  obtain  a  complete 
perception  of  its  sapid  qualities.  For  at  that  time  the  food  is  spread 
out  by  the  compression  of  the  muscles,  and  brought  at  once  in 
contact  with  the  entire  extent  of  the  mucous  membrane  possessing 
gustative  sensibility.     Then,  it  is  no  longer  under  the  control  of  the 


TASTE.  487 

will,  -and  is  carried  by  the  reflex  actions  of  the  pharynx  and  oeso- 
phagus downward  to  the  stomach. 

The  impressions  of  taste  made  upon  the  tongue  remain  for  a  cer- 
tain time  afterward.  When  a  very  sweet  or  very  bitter  substance 
is  taken  into  the  mouth,  we  retain  the  taste  of  its  sapid  qualities 
for  several  seconds  after  it  has  been  ejected  or  swallowed.  Conse- 
quently, if  several  different  savors  be  presented  to  the  tongue  in 
rapid  succession,  we  soon  become  unable  to  distinguish  them,  and 
they  produce  only  a  confused  impression,  made  up  of  the  union  of 
various  different  sensations ;  for  the  taste  of  the  first,  remaining  in 
the  mouth,  is  mingled  with  that  of  the  second,  the  taste  of  these 
two  with  that  of  the  third,  and  so  on,  until  so  many  savors  become 
confounded  together  that  we  are  no  longer  able  to  recognize  either 
of  them.  Thus  it  is  notoriously  impossible  to  recognize  two  or 
three  different  kinds  of  wine  with  the  eyes  closed,  if  they  be  repeat- 
edly tasted  in  quick  succession. 

If  the  substance  first  tasted  have  a  particularly  marked  savor, 
its  taste  will  preponderate  over  that  of  the  others,  and  perhaps  pre- 
vent our  recognizing  them  at  all.  This  effect  is  still  more  readily 
produced  by  substances  which  excite  the  general  sensibility  of  the 
tongue,  such  as  acrid  or  stimulating  powders.  In  the  same  manner 
as  a  painful  sensation,  excited  in  the  skin,  prevents  the  nerves,  for 
the  time,  from  perceiving  delicate  tactile  impressions,  so  any  pungent 
or  irritating  substance,  which  excites  unduly  the  general  sensibility 
of  the  tongue,  blunts  for  a  time  its  special  sensibility  of  taste.  This 
effect  is  produced,  however,  in  the  greatest  degree,  by  substances 
which  are  at  the  same  time  sapid,  pungent  and  aromatic,  like  sweet- 
meats flavored  with  peppermint.  Advantage  is  sometimes  taken 
of  this  in  the  administration  of  disagreeable  medicines.  By  first 
taking  into  the  mouth  some  highly  flavored  and  pungent  substance, 
nauseous  drugs  may  be  swallowed  immediately  afterward  with  but 
little  perception  of  their  disagreeable  qualities. 

A  very  singular  fact,  in  connection  with  the  sense  of  taste,  is  that 
it  is  sometimes  affected  in  a  marked  degree  hy  paralysis  of  the  facial 
nerve.  No  less  than  six  cases  of  this  kind,  occurring  in  the  human 
subject,  have  been  collected  by  M.  Bernard,  and  we  have  also  met 
with  a  similar  instance  in  which  the  peculiar  phenomena  were  well 
marked.  M.  Bernard  has  furthermore  seen  a  similar  effect  upon 
the  taste  produced  in  animals  by  division  of  the  facial  nerve  within 
the  cranium.  The  result  of  these  experiments  and  observations  is 
as  follows:  AVhen  the  facial  nerve  is  divided  or  seriously  injured 


488  THE    SPECIAL    SENSES. 

by  organic  disease,  before  its  emergence  from  the  stylo-mastoid 
foramen,  not  only  is  there  a  paralysis  of  the  superficial  muscles  of 
the  face,  but  the  sense  of  taste  is  diminished  on  the  corresponding 
side  of  the  tongue.  If  the  tongue  be  protruded,  and  salt,  citric  acid 
or  sulphate  of  quinine  be  placed  upon  its  surface  on  the  two  sides 
.  of  the  median  line,  the  taste  of  these  substances  is  perceived  on  the 
affected  side  more  slowly  and  obscurely  than  on  the  other.  It  is 
not,  therefore,  a  destruction,  but  only  a  diminution  of  the  sense  of 
taste,  which  follows  paralysis  of  the  facial  in  these  instances.  At 
the  same  time  the  general  tactile  sensibility  of  the  tongue  is  unal- 
tered, retaining  its  natural  acuteness  on  both  sides  of  the  tongue. 

The  exact  mechanism  of  this  peculiar  influence  of  the  facial  nerve 
npon  the  sense  of  taste  is  not  perfectly  understood.  It  may  be 
considered  as  certain,  however,  that  it  is  derived  through  the 
medium  of  that  branch  of  the  facial  nerve  known  as  the  chorda 
tympani.  This  filament  leaves  the  facial  at  the  intumescentia 
gangliformis,  in  the  interior  of  the  aqueduct  of  Fallopius,  enters  the 
cavity  of  the  tympanum,  passes  across  the  membrane  of  the  tym- 
panum, and  then,  emerging  from  the  cranium,  runs  downward  and 
forward  and  joins  the  lingual  branch  of  the  fifth  pair.  It  then  ac- 
companies this  nerve  as  far  as  the  posterior  extremity  of  the  sub- 
maxillary gland.  Here  it  divides  into  two  portions ;  one  of  which 
passes  to  the  submaxillary  ganglion,  and,  through  it,  to  the  sub- 
stance of  the  submaxillary  gland,  while  the  other  continues  onward, 
still  in  connection  with  the  lingual  branch  of  the  fifth  pair,  and,  in 
company  with  the  filaments  of  this  nerve,  is  distributed  to  the  tongue. 

The  chorda  tympani  thus  forms  the  only  anatomical  connection 
between  the  facial  nerve  and  the  anterior  part  of  the  tongue.  When 
the  facial,  accordingly,  is  divided  or  injured  after  its  emergence 
from  the  stylo-mastoid  foramen,  no  effect  is  produced  upon  the 
sense  of  taste ;  but  when  it  is  injured  during  its  course  through  the 
aqueduct  of  Fallopius,  and  before  it  has  given  off  the  chorda  tym- 
pani, this  nerve  suffers  at  the  same  time,  and  the  sense  of  taste  is 
diminished  in  activity,  as  above  described.  It  is  probable  that  this 
effect  is  produced  in  an  indirect  way,  by  a  diminution  in  the  activity 
of  secretion  in  the  lingual  follicles,  or  by  some  alteration  in  the 
vascularity  of  the  parts. 

Smell. — The  main  peculiarity  of  the  sense  of  smell  consists  in 
the  fact  that  it  gives  us  intelligence  of  the  physical  character  of 
bodies  in  a  gaseous  or  vaporous  condition.     Thus  we  are  enabled  to 


SMELL. 


489 


perceive  the  existence  of  an  odorous  substance  at  a  distance,  and 
when  it  is  altogether  concealed  from  sight.  The  minute  quantity 
of  volatile  material  emanating  from  it,  and  thus  pervading  the 
atmosphere,  comes  in  contact  with  the  mucous  membrane  of  the 
nose,  and  produces  a  peculiar  and  special  sensation. 

The  apparatus  of  this  sense  consists,  first,  of  the  olfactory  mem- 
brane, supplied  by  the  filaments  of  the  olfactory  nerve,  as  its 
special  organ ;  and  secondly,  of  the  nasal  passages,  with  the  tur- 
binated bones  and  the  muscles  of  the  anterior  and  posterior  nares, 
as  its  accessory  organs.  At  the  upper  part  of  the  nasal  fossae, 
the  mucous  membrane  is  very  thick,  soft,  spongy  and  vascular, 
and  is  .supplied  with  mucous  follicles  which  exude  a  secretion,  by 
which  its  surface  is  protected  and  kept  in  a  moist  and  sensitive 
condition. 

It  is  only  this  portion  of  the  mucous  membrane  of  the  nares 
which  is  supplied  by  filaments  of  the  olfactory  nerve,  and  which  is 
capable  of  receiving  the  impressions  of  smell ;  it  is  therefore  called 
the  Olfactory  membrane.  Elsewhere,  the  nasal  passages  are  lined 
with  a  mucous  membrane  which  is  less  vascular  and  spongy  in 
structure,  and  which  is  called  the  Schneiderian  membrane. 

The  filaments  derived  from  the  olfactory  ganglia,  and  which 
penetrate  through  the  cribri- 
form plate  of  the  ethmoid  ^^^'  ^^^' 
bone,  are  distributed  to  the 
mucous  membrane  of  the  su- 
perior and  middle  turbinated 
bones,  and  to  that  of  the  upper 
part  of  the  septum  nasi.  The 
exact  mode  in  which  these 
filaments  terminate  in  the  ol- 
factory membrane  has  not 
been  definitely  ascertained. 
They  are  of  a  soft  consistency 
and  gray  color,  and,  after  di- 
viding and  ramifying  freely 
in  the  membrane,  appear  to 
become  lost  in  its  substance. 
It  is  these  nerves  which  exer- 
cise the  special  function  of 
smell.  They  are,  to  all  appearance,  incapable  of  receiving  ordinary 
impressions,  and  must   be    regarded  as  entirely  peculiar  in  their 


DlSTRIBtTTION     OP      NeRVES     IN     THE     N  A  S  A  I, 

Passages. — 1.  Olfactory  ganglion,  withits  nerves 
2.  Nasal  branch  of  fifth  pair.  3.  Spheuo-palatiue 
gaugliou. 


490  THE    SPECIAL    SENSES. 

nature  and  endowments.  The  nasal  passages,  however,  are  supplied 
with  other  nerves  beside  the  olfactory.  The  nasal  branch  of  the 
ophthalmic  division  of  the  fifth  pair,  after  entering  the  anterior  part 
of  the  cavity  of  the  nares,  just  in  advance  of  the  cribriform  plate  of 
the  ethmoid  bone,  is  distributed  to  the  mucous  membrane  of  the  in- 
ferior turbinated  bone  and  the  inferior  meatus.  Thus  the  organ 
of  smell  is  provided  with  sensitive  nerves  from  two  different  sources, 
viz.,  at  its  upper  part,  with  the  olfactory  nerves  proper,  derived 
from  the  olfactory  ganglion  (Fig.  154,  i),  which  are  nerves  of  special 
sensation ;  and  secondly,  at  its  lower  part,  with  the  nasal  branch  of 
the  fifth  pair  (2),  a  nerve  of  general  sensation.  Beside  which,  the 
spheno-palatine  ganglion  of  the  great  sympathetic  (3)  sends  fila- 
ments to  the  mucous  membrane  of  the  whole  posterior  part  of  the 
nasal  passages,  and  to  the  levator  palati  and  azygos  uvulae  muscles. 
Finally,  the  muscles  of  the  anterior  nares  are  supplied  by  filaments 
of  the  facial  nerve. 

The  conditions  of  the  sense  of  smell  are  much  more  special  in 
their  nature  than  those  of  taste.  For,  in  the  first  place,  this  sense  is 
excited,  not  by  actual  contact  with  the  foreign  body,  but  only  with 
its  vaporous  •  emanations ;  and  the  quantity  of  these  emanations, 
sufficient  to  excite  the  smell,  is  often  so  minute  as  to  be  altogether 
inappreciable  by  other  means.  We  cannot  measure  the  loss  of 
weight  in  an  odorous  body,  though  it  may  affect  the  atmosphere 
of  an  entire  house,  and  the  senses  of  all  its  inhabitants,  for  days 
and  weeks  together.  Secondly,  in  the  olfactory  organ,  the  special 
sensibility  of  smell  and  the  general  sensibility  of  the  mucous  mem- 
brane are  separated  from  each  other  and  provided  for  by  different 
nerves,  not  mingled  together  and  exercised  by  the  same  nerves,  as 
is  the  case  in  the  tongue. 

In  order  to  produce  an  olfactory  impression,  the  emanations  of 
the  odorous  body  must  be  drawn  freely  through  the  nasal  passages. 
As  the  sense  of  smell,  also,  is  situated  only  in  the  upper  part  of  these 
passages,  whenever  an  unusually  faint  or  delicate  odor  is  to  be  per- 
ceived, the  air  is  forcibly  directed  upward,  toward  the  superior 
turbinated  bones,  by  a  peculiar  inspiratory  movement  of  the  nos- 
trils. This  movement  is  very  marked  in  many  of  the  lower  animals. 
As  the  odoriferous  vapors  arrive  in  the  upper  part  of  the  nasal 
passages,  they  are  undoubtedly  dissolved  in  the  secretions  of  the 
olfactory  membrane,  and  thus  brought  into  relation  with  its  nerves. 
Inflammatory  disorders,  therefore,  interfere  with  the  sense  of  smell, 
both  by  checking  or  altering  the  secretions  of  the  part,  and  by 


SMELL.  491 

producing  fin  unnatural  tumefaction  of  the  mucous  membrane, 
which  prevents  the  free  passage  of  the  air  through  the  nasal  fossae. 

As  in  the  case  of  the  tongue,  also,  we  must  distinguish  here 
between  the  perception  of  true  odors,  and  the  excitement  of  the 
general  sensibility  of  the  Schneiderian  mucous  membrane  by  irri- 
tating substances.  Some  of  the  true  odors  are  similar  in  their  nature 
to  impressions  perceived  by 'the  sense  of  taste.  Thus  we  have 
sweet  and  sour  smells,  though  none  corresponding  to  the  alkaline 
or  the  bitter  tastes.  Most  of  the  odors,  however,  are  of  a  very 
peculiar  nature  and  are  difficult  to  describe ;  but  they  are  always 
distinct  from  the  simply  irritating  properties  which  may  belong  to 
vapors  as  well  as  to  liquids.  Thus,  pure  alcohol  has  little  or  no 
odor,  and  is  only  irritating  to  the  mucous  membrane ;  while  the 
odor  of  wines,  of  cologne  water,  &c.,  is  communicated  to  them  by 
the  presence  of  other  ingredients  of  a  vegetable  origin.  In  the 
same  way,  pure  acetic  acid  is  simply  irritating ;  while  vinegar  has 
a  peculiar  odor  in  addition,  derived  from  its  vegetable  impurities. 
Ammonia,  also,  is  an  irritating  vapor,  but  contains  in  itself  no 
odoriferous  principle. 

The  sensations  of  smell,  like  those  of  taste,  remain  for  a  certain  time 
after  they  have  been  produced,  and  modify  in  this  way  other  less 
strongly  marked  odors  which  are  presented  afterward.  As  a 
general  thing,  the  longer  we  are  exposed  to  a  particular  odor,  the 
longer  its  effect  upon  our  senses  continues ;  and  in  some  cases  it 
may  be  perceived  many  hours  after  the  odoriferous  substance  has 
been  removed.  Odors,  however,  are  particularly  apt  to  remain 
after  the  removal  or  destruction  of  the  source  from  which  they 
were  derived,  owing  to  their  vaporous  character,  and  the  facility 
with  which  they  are  entangled  and  retained  by  porous  substanceS; 
such  as  plastered  walls,  woollen  carpets,  and  hangings,  and  woollen 
clothes.  It  is  supposed  to  be  in  this  way  that  the  odor  of  a  post- 
mortem examination  will  sometimes  remain  so  as  to  be  perceptible 
for  several  hours  or  even  an  entire  day  afterward.  But  this  alone 
does  not  fully  explain  the  fact.  For  if  it  depended  simply  on  the 
retention  of  the  odor  by  porous  substances,  it  would  afterward  be 
perceived  constantly,  until  it  gradually  and  continuously  wore  off; 
while  in  point  of  fact,  the  physician  who  has  made  an  autopsy  of 
this  kind  does  not  afterward  perceive  its  odor  constantly,  but  only 
occasionally,  and  by  sudden  and  temporary  fits. 

The  explanation  is  probably  this.  As  the  odor  remains  con- 
stantly by  us,  we  soon  become  insensible  to  its  presence,  as  in  the 


492  THE    SPECIAL    SENSES. 

case  of  all  other  continuous  and  unvarying  impressions.  Our  at- 
tention is  only  called  to  it  when  we  meet  suddenly  with  another 
and  familiar  odor.  This  second  odor,  we  find,  does  not  produce  its 
usual  impression,  becaase  it  is  mingled  with  and  modified  by  the 
other,  which  is  more  persistent  and  powerful.  Thus  we  are  again 
made  aware  of  the  former  one,  to  which  we  had  become  insensible 
by  reason  of  its  constant  presence. 

The  sense  of  smell  is  comparatively  feeble  in  the  human  species, 
but  is  excessively  acute  in  some  of  the  lower  animals.  Thus,  the 
dog  will  not  only  distinguish  different  kinds  of  game  in  the  forest 
by  this  sense,  and  follow  them  by  their  tracks,  but  will  readily  dis- 
tinguish particular  individuals  by  their  odor,  and  will  recognize 
articles  of  dress  belonging  to  them  by  the  minute  quantity  of  odor- 
iferous vapors  adhering  to  their  substance. 

Sight. — The  sight  undoubtedly  occupies  the  first  rank  in  the 
list  of  special  nervous  endowments.  It  is  the  most  peculiar  in  its 
operation,  and  the  most  immaterial  in  its  nature,  of  all  the  senses, 
and  it  is  through  it  that  we  receive  the  most  varied  and  valuable 
impressions.  The  physical  agent,  also,  to  which  the  organ  of  sight 
is  adapted,  and  by  which  its  sensibility  is  excited,  is  more  subtle 
and  peculiar  than  any  of  those  which  act  upon  our  other  senses. 
For  the  senses  of  touch,  taste,  and  smell  require,  for  their  exercise, 
the  actual  contact  of  a  foreign  body,  either  in  a  solid,  liquid,  or 
aeriform  condition;  and  even  the  hearing  depends  upon  the  me- 
chanical vibrations  of  the  atmosphere,  or  some  other  sonorous 
medium.  But  the  eye  does  not  need  to  be  in  contact  with  the 
luminous  body.  It  will  receive  the  impressions  of  light  with  per- 
fect distinctness,  even  when  they  are  transmitted  from  an  immea- 
surable distance,  as  in  the  case  of  the  fixed  stars ;  and  the  light 
itself  is  not  only  immaterial  in  its  nature,  so  far  as  we  can  ascertain, 
but  is  also  capable  of  being  transmitted  through  space  without  the 
intervention  of  any  material  conducting  medium,  yet  discoverable. 

Finally,  the  apparatus  of  vision  is  more  complicated  in  its  struc- 
ture than  that  of  any  other  of  the  special  senses.  This  apparatus 
consists,  first,  of  the  retina,  as  a  special  sensitive  nervous  membrane ; 
and  secondly,  of  the  vitreous  body,  crystalline  lens,  choroid,  scle- 
rotic, iris  and  cornea,  together  with  the  muscles  moving  the  eye- 
ball and  eyelids,  lachrymal  gland,  &c.,  as  accessory  organs.  The 
arrangement  of  the  parts,  constituting  the  globe  of  the  eye,  is  shown 
in  the  following  figure.  (Fig.  155.) 


SIGHT. 


49c 


The  filaments  of  the  optic  nerve,  after  running  forward  and  pene- 
trating the  posterior  part  of  the  eyeball,  spread  out  into  the  sub- 
stance of  the  retina  (3),  thus  forming  a  delicate  and  vascular  nerv- 


Vertical  Section  of  the  Eyeball.— 1.  Sclerotic.    2    Choroid.    .3. 
jnembrane.     6.  Curoea.     7.  Iris.     8.  Ciliary  muscle  and  processes. 


Retina.    4.  Lens.    5.  Hyalosd 


ous  expansion,  in  the  form  of  a  spheroidal  bag  or  sac,  with  a  wide 
opening  in  front,  where  the  retina  terminates  at  the  posterior  mar- 
gin of  the  ciliary  body.  This  expansion  of  the  retina  is  the  essen- 
tial nervous  apparatus  of  the  eye.  It  is  endowed  with  the  special 
sensibility  which  renders  it  capable  of  receiving  luminous  impres- 
sions ;  and,  so  far  as  we  have  been  able  to  ascertain,  it  is  incapable  of 
perceiving  any  other.  On  the  outside,  the  retina  is  covered  by  the 
choroid  coat  (2),  a  vascular  membrane,  which  is  rendered  opaque  by 
the  presence  of  an  abundant  layer  of  blackish-brown  pigment-cells, 
and  which  thus  absorbs  the  light  which  has  once  passed  through 
the  retina,  and  prevents  its  being  reflected  in  such  a  way  as  to 
confuse  and  dazzle  the  sight.  Inside  the  retina  is  the  vitreous  lady, 
a  transparent  spheroidal  mass  of  a  gelatinous  consistency,  which  is 
surrounded  and  retained  in  position  by  a  thin,  structureless  mem- 
brane, called  the  hyaloid  membrance  (5),  lying  immediately  in 
contact  with  the  internal  surface  of  the  retina.  The  lens  (4)  is 
placed  in  front  of  the  vitreous  body,  in  the  central  axis  of  the  eye- 
ball, enveloped  in  its  capsule,  which  is  continuous  with  the  hyaloid 
membrane.  Just  at  the  edge  of  the  lens,  the  hyaloid  membrane 
divides  into  two  laminae,  which  separate  from  each  other,  leaving 
between  them  a  triangular  canal,  the  canal  of  Petit,  which  can  be 
seen  in  the  above  figure.    In  front  of  the  lens  is  the  iris{'i),  a  nearly 


494  THE    SPECIAL    SENSES. 

vertical  muscular  curtain,  formed  of  radiating  and  concentric  fibres, 
pierced  at  its  centre  with  a  circular  opening,  the  pupil,  through 
which  the  light  is  admitted,  and  covered  on  its  posterior  surface 
with  a  continuation  of  the  choroidal  pigment,  which  excludes  the 
passage  of  any  other  rays  than  those  which  pass  through  the  pupil. 
At  the  same  time,  the  whole  globe  is  inclosed  and  protected  by  a 
thick,  fibrous,  laminated  tunic,  which  in  its  posterior  and  middle 
portions  is  opaque,  forming  the  sclerotic  (i),  and  in  its  anterior  por- 
tion is  transparent,  forming  the  cornea  (s).  The  muscles  of  the  eye- 
ball are  attached  to  the  external  surface  of  the  sclerotic  in  such  a 
way  that  the  cornea  may  be  readily  turned  in  various  directions ; 
while  the  eyelids,  which  may  be  opened  and  closed  at  will,  protect 
the  eye  from  injury,  and,  with  the  aid  of  the  lachrymal  secretion, 
keep  its  anterior  surfaces  moist,  and  preserve  the  transparency  of 
the  cornea. 

The  organ  of  vision  is  supplied  with  nerves  of  ordinary  sensi- 
bility by  the  ophthalmic  branch  of  the  fifth  pair.  The  filaments 
of  this  nerve  which  terminate  about  the  eye  are  distributed  mostly 
to  the  conjunctiva,  lachrymal  gland,  and  skin  of  the  eyelids ;  while 
a  very  few  of  them  run  forward  in  company  with  the  ciliary  nerves 
proper,  and  are  distributed  to  the  ciliary  circle  and  iris.  All  these 
parts,  therefore,  but  more  particularly  the  conjunctiva  and  skin  of 
the  eyelids,  possess  ordinary  sensibility,  which  appears  to  be  totally 
wanting  in  the  deeper  parts  of  the  eye.  The  ophthalmic  ganglion 
gives  ofi'  the  ciliary  nerves,  which  are  distributed  to  the  iris  and 
ciliary  muscle.  Finally,  the  muscles  moving  the  eyeball  and  eye- 
lids are  supplied  with  motor  nerves  from  the  third,  fourth,  sixth 
and  seventh  pairs. 

Of  all  the  properties  and  functions  belonging  to  the  different 
structures  of  the  eyeball,  the  most  peculiar  and  characteristic  is  the 
special  sensibility  of  the  retina.  This  sensibility  is  such  that  the 
retina  appreciates  both  the  intensity  and  the  quality  of  the  light — 
that  is  to  say,  its  color  and  the  different  shades  which  this  color 
may  present.  On  account  of  the  form,  also,  in  which  the  retina  is 
constructed,  viz.,  that  of  a  spheroidal  membranous  bag,  with  an 
opening  in  front,  it  becomes  capable  of  appreciating  the  direction 
from  which  the  rays  of  light  have  come,  and,  of  course,  the  situation 
of  the  luminous  body  and  of  its  different  parts.  For  the  rays  which 
enter  through  the  pupil  from  below  can  reach  the  retina  only  at  its 
upper  part,  while  those  which  come  in  from  above,  can  reach  it 
only  at  its  lower  part ;  so  that  in  both  instances  the  rays  strike  the 


SIGHT. 


495 


sensitive  surface  perpendicularly,  and  thus  convey  the  impression 
of  their  direction  from  above  or  below. 

But  beside  the  sensibility  of  the  retina,  the  perfection  and  value 
of  the  sense  of  sight  depend  very  much  on  the  arrangement  of  the 
accessory  organs,  the  most  important  of  which  is  the  crystalline  lens. 

The  function  of  the  crystalline  Itns  is  to  j^i'oduce  distinct  perception 
of  form,  and  outline.  For  if  the  eye  consisted  merely  of  a  sensitive 
retiua,  covered  with  transparent  integument,  though  the  impressions 
of  light  would  be  received  by  such  a  retina  they  could  not  give 
any  idea  of  the  form  of  particular  objects,  but  could  only  produce 
the  sensation  of  a  confused  luminosity.  This  condition  is  illus- 
trated in  Fig.  156,  where  the  arrow,  a,  h,  represents  the  luminous 
object,  and  the  vertical  dotted  line,  at  the  right  of  the  diagram, 
represents  the  retina.  Eays,  of  course,  will  diverge  from  every 
point  of  the  object  in  every  direction,  and  will  thus  reach  every 
part  of  the  retina.  The  different  parts  of  the  retina,  consequently, 
1,  2,  3,  4,  will  each  receive  rays  coming  both  from  the  point  of  the 
arrow,  a,  and  from  its  butt,  h.  There  will  therefore  be  no  distinc- 
tion, upon  the  retina,  between  the  different  parts  of  the  object,  and  no 


Fig.  156. 


Fig.  Wi. 


definite  perception  of  its  outline.  But  if,  between  the  object  and  the 
retina,  there  be  inserted  a  double  convex  refracting  lens,  with  the 
proper  curvatures  and  density,  as  in  Fig.  157,  the  effect  will  be  dif- 
ferent. For  then  all  the  rays  emanating  from  a  will  be  concentrated 
at  X,  and  all  those  emanating  from  h  will  be  concentrated  at  y. 
Thus  the  retina  will  receive  the  impression  of  the  point  of  the 
arrow  separate  from  that  of  the  butt ;  and  all  parts  of  the  object, 
in  like  manner,  will  be  distinctly  and  accurately  perceived. 

This  convergence  of  the  rays  of  light  is  accomplished  to  a  certain 
extent  by  the  other  transparent  and  refracting  parts  of  the  eyeball ; 
but  the  lens  is  the  most  important  of  all  in  this  respect,  owing  to 
its  superior  density  and  the  double  convexity  of  its  figure.  The 
distinctness  of  vision,  therefore,  depends  upon  the  action  of  the 


496 


THE    SPECIAL    SENSES. 


lens  in  converging  all  the  rays  of  light,  emanating  from  a  given 
point,  to  an  accurate  focus,  at  the  surface  of  the  retina.  To  accomplisli 
this,  the  density  of  the  lens,  the  curvature  of  its  surfaces,  and  its 
distance  from  the  retina,  must  all  be  accurately  adapted  to  each 
other.  For  if  the  lens  be  too  convex,  and  its  refractive  power  con- 
sequently too  great,  the  rays  will  be  converged  to  a  focus  too  soon, 
and  will  not  reach  the  retina  until  after  they  have  crossed  each 
other  and  become  partially  dispersed,  as  in  Fig.  158.  The  visual 
impression,  therefore,  coming  from  any  particular  point  in  the 
object  is  not  concentrated  and  distinct,  but  difl'used  and  dim,  from 
being  dispersed  more  or  less  over  the  retina,  and  interfering  with 
the  impressions  coming  from  other  parts.  This  is  the  condition 
which  is  present  in  myopia,  or  near-sightedness.    On  the  other  hand, 


Fig.  158. 


Fig.  159. 


Myopia. 


PilESBTOPIA. 


if  the  lens  be  too  flat,  and  its  convergent  power  too  feeble,  as  in 
Fig.  159,  the  rays  will  fail  to  come  together  at  all,  and  will  strike 
the  retina  separately,  producing  a  confused  image,  as  before.  This 
is  the  defect  which  exists  in  presbyopia,  or  long-sightedness.  In 
both  cases,  the  immediate  cause  of  the  confusion  of  sight  is  the 
same,  viz.,  the  rays  coming  from  the  same  point  of  the  object 
striking  the  retina  at  different  points ;  but  in  the  first  instance,  this 
is  because  the  rays  have  actually  converged,  and  then  crossed ;  in 
the  second,  it  is  because  they  have  only  approached  each  other,  but 
have  never  converged  to  a  focus. 

Another  important  particular  in  regard  to  the  action  of  the  lens 
is  the  accommodation  of  the  eye  to  distinct  vision  at  different  distances. 
It  is  evident  that  the  same  arrangement  of  the  refractive  parts,  in 
the  eye,  will  not  produce  distinct  vision  when  the  distance  of  the 
object  from  the  eye  is  changed.  If  this  arrangement  be  such  that 
the  object  is  seen  distinctly  at  a  certain  distance,  as  in  Fig.  160, 
and  the  object  be  then  removed  to  a  remoter  point,  as  in  Fig.  161, 
the  image  will  become  confused ;  for  the  rays  will  then  be  con- 


SIGHT. 


497 


verged  to  a  focus  at  a  point  in  front  of  the  retina ;  because,  being 
less  divergent,  wben  they  strike  the  lens,  the  same  amount  of  re- 
fraction will  bring  them  together  sooner  than  before.  On  the  other 
hand,  if  the  object  be  moved  to  a  point  nearer  the  eye,  the  rays, 
becoming  more  divergent  as  they  strike  the  lens,  will  be  converged 
less  rapidly  to  a  focus,  and  vision  will  again  become  indistinct. 

This  may  easily  be  seen  by  the  aid  of  a  very  simple  experiment. 
If  two  needles  be  placed  upright,  at  different  distances  from  the  eye, 
one  for   example   at   eight  and  p.     ^^^ 

the  other  at  eighteen  inches,  but 
nearly  in  the  same  linear  range, 
and  if  then,  closing  one  eye,  we 
look  at  them  alternately,  we  shall 
find  that  we  cannot  see  both  dis- 
tinctly at  the  same  time.  For 
when  we  look  at  the  one  near- 


Fig.  161. 


est  the  eye,  so  as  to  perceive  its  form  distinctly,  the  image  of  the 
more  remote  one  becomes  confused ;  and  when  we  see  the  more  re- 
mote object  in  perfection,  that  which  is  nearer  loses  its  sharpness  of 
outline.  This  shows,  in  the  first  place,  that  the  same  condition  of 
the  eye  will  not  allow  us  to  see  two  objects  at  different  distances 
with  distinctness  at  the  same  time ;  and  secondly  that,  on  looking 
from  one  to  the  other,  there  is  a  change  of  some  kind  in  the  focus  of 
the  eye,  by  which  it  is  adapted  to  different  distances.  Indeed  we 
are  conscious  of  a  certain  effort  at  the  time  when  the  point  of  vision 
is  transferred  from  one  object  to  the  other,  by  which  the  eye  is 
adapted  to  the  new  distance ;  and  this  alteration  is  not  quite  instan- 
taneous, but  requires  a  certain  interval  of  time  for  its  completion. 
This  accommodation  of  the  eye  to  different  distances  is  un- 
doubtedly effected  by  an  antero-posterior  movement  of  the  lens 
within  the  eyeball.  It  will  at  once  be  perceived,  on  referring  to 
Fig.  161,  that  if  the  lens  were  moved  a  little  backward  toward  the 


498  THE    SPECIAL    SENSES. 

retina,  at  the  same  time  that  the  object  is  removed  to  a  greater  dis- 
tance from  the  eye,  the  focus  of  the  convergent  rays  would  still  fall 
upon  the  retina,  and  the  image  would  still  be  distinct.  In  the  op- 
posite case,  where  the  object  is  brought  nearer  the  eye,  a  similar 
movement  of  the  lens  forward  would  again  secure  perfect  vision. 
Thus,  when  we  look  at  near  objects,  the  lens  moves  forward 
toward  the  pupil ;  when  we  look  at  remote  objects,  it  moves  back- 
ward toward  the  retina. 

This  movement  of  the  lens  is  apparently  accomplished  by  the 
action  of  the  ciliary  muscle.  This  muscle  (Fig.  155,  6)  arises,  in 
front,  from  the  conjunction  of  the  sclerotic  and  the  cornea,  and  run- 
ning backward  and  outward,  is  inserted  into  the  anterior  part  of 
the  choroid,  about  the  situation  at  which  the  hyaloid  membrane 
passes  off,  to  become  the  suspensory  ligament  of  the  lens.  As 
already  mentioned,  this  muscle  is  supplied  with  nervous  filaments 
from  the  ophthalmic  ganglion.  Its  action  is  to  draw  the  lens  for- 
ward, by  means  of  its  attachment  to  the  hyaloid  membrane  and 
choroid  coat ;  and,  in  the  human  subject,  the  retreat  or  retrogres- 
sion of  the  lens  toward  the  retina,  after  the  ciliary  muscle  is  relaxed, 
seems  to  be  due  to  the  elastic  resiliency  of  the  remaining  tissues  of 
the  eyeball. 

But  in  order  to  allow  of  such  a  backward  and  forward  movement 
of  the  lens,  since  the  liquids  of  the  eyeball  are  incompressible,  there 
must  be  a  corresponding  displacement  of  other  parts,  both  before 
and  behind.  This  is  undoubtedly  provided  for  by  the  vascularity 
of  the  choroid  coat.  This  membrane  is  supplied  with  an  exceedingly 
abundant  vascular  plexus  over  its  whole  posterior  portion ;  and  in 
front  it  is  thrown  into  a  circle  of  prominent  converging  folds,  or 
processes,  the  ciliary  processes,  which  are  nothing  more  than  erectile 
congeries  of  bloodvessels,  covered  with  the  pigment  of  the  choroid. 
A  portion  of  the  ciliary  processes  projects  in  front  of  the  lens,  and 
their  vascular  network  is  continued  over  a  great  part  of  the  pos- 
terior surface  of  the  iris.  Thus  there  is,  both  behind  and  in  front 
of  the  lens,  an  erectile  system  of  bloodvessels ;  and  as  these  blood- 
vessels become  alternately  empty  or  turgid,  they  will  allow  of  the 
displacement  of  the  lens  in  an  anterior  or  posterior  direction. 

Accordingly  there  is  a  certain  accommodation  of  the  eye  neces- 
sary to  the  distinct  sight  of  objects  at  different  distances.  But  the 
range  of  this  accommodation  is  limited,  and  the  same  eye  cannot  be 
made  to  see  distinctly  at  all  distances.  For  all  ordinary  eyes,  the 
accommodation  fails,  and  vision  becomes  imperfect,  when  the  object 


SIGHT.  499 

is  placed  at  less  than  six  inches  distance  from  the  eye.  But  from 
that  point  outward,  the  eye  can  adapt  itself  to  any  distance  at  which 
light  is  perceptible,  even  to  the  immeasurable  distances  of  the  fixed 
stars.  A  much  greater  accommodating  power,  however,  is  re- 
quired for  near  distances  than  for  remote,  since  the  diflerence  in 
divergence  between  rays,  entering  the  pupil  from  a  distance  of  one 
inch  and  from  that  of  six  inches,  is  greater  than  the  difference  be- 
tween six  inches  and  a  yard,  or  even  distances  which  are  immea- 
surably remote.  Accordingly,  near-sighted  persons  can  see  objects 
distinctly  when  placed  very  near  the  eye;  since,  as  their  lens  con- 
verges the  rays  of  light  more  powerfully  than  usual,  they  can  be 
brought  to  a  focus  upon  the  retina,  even  when  excessively  diverg- 
ent at  the  time  they  enter  the  eye.  But  distant  objects  become 
indistinct,  since,  however  far  backward  the  lens  is  moved,  the  rays 
are  still  brought  to  a  focus  and  cross  each  other,  before  reaching 
the  retina,  as  in  Fig.  161.  Near-sighted  persons,  therefore,  have  a 
limited  range  of  accommodation,  like  all  others,  only  it  is  confined 
within  short  distances,  owing  to  the  excessive  refracting  power  of 
the  lens. 

On  the  other  hand,  long-sighted  persons  can  see  remote  objects 
without  trouble,  since  a  very  little  movement  of  the  lens  will  be 
sufiicient  to  adapt  it  for  long  distances ;  but  within  short  distances, 
the  divergence  of  the  rays  becomes  too  great,  and  they  cannot  be 
brought  to  a  focus. 

Circle  of  Vision. — Since  the  opening  of  the  pupil  will  admit  rays 
of  light  coming  from  various  directions,  there  is  in  front  of  the  eye 
a  circle,  or  space,  within  which  luminous  objects  are  perceived,  and 
beyond  which  nothing  can  be  seen,  because  the  rays,  coming  from 
the  side  or  from  behind,  cannot  enter  the  pupil.  This  space,  within 
which  external  objects  can  be  perceived,  is  called  the  "  circle  of 
vision."  But,  for  short  distances,  there  is  only  a  single  point,  in  the 
centre  of  the  circle  of  vision,  at  which  objects  can  be  seen  distinctly. 
Thus,  if  we  place  ourselves  in  front  of  a  row  of  vertical  stakes  or 
palisades,  we  can  see  those  directly  in  front  of  the  eye  with  perfect 
distinctness,  but  those  at  a  little  distance  on  each  side  are  only  per- 
ceived in  a  confused  and  uncertain  manner.  On  looking  at  the 
middle  of  a  printed  page,  in  the  direct  range  of  vision,  we  see  the 
distinct  outlines  of  the  letters ;  while  at  successive  distances  from 
this  point,  the  eye  remaining  fixed,  we  can  distinguish  first  only 
the  separate  letters  with  confused  outlines,  then  only  the  words,  and 
lastly  only  the  lines  and  spaces. 


500 


THE    SPECIAL    SENSES. 


This  is  because  rays  of  light  coming  into  the  eye  very  obliquely, 
in  a  lateral  or  vertical  direction,  are  not  brought  to  their  proper  focus. 
Thus,  in  Fig.  162,  the  rays  diverging  from  the  point  a,  directly  in 
front  of  the  eye,  fall  upon  the  lens  in  such  a  way  that  they  are  all 
brought  together  at  x,  at  the  surface  of  the  retina ;  but  those  coming 
from  h  fall  upon  the  lens  so  obliquely  that,  for  rays  having  an  equal 
divergence  with  those  coming  from  a,  there  is  more  difference  in  their 
angles  of  incidence,  and  of  course  more  difference  in  the  amount 
of  their  refraction.  They  are  consequently  brought  together  more 
rapidly,  and  on  reaching  the  retina  are  dispersed  over  the  space  y,  z. 

Fig.  162. 


The  perfection  of  the  eye,  as  a  visual  apparatus,  is  very  much 
increased  by  the  action  of  the  iris.  This  organ,  as  we  have  already 
mentioned,  is  a  nearly  vertical  muscular  curtain,  placed  in  front  of 
the  lens,  attached  by  its  external  margin  to  the  junction  of  the 
cornea  and  sclerotic,  and  pierced  about  its  centre  by  the  circular 
opening  of  the  pupil.  It  consists,  according  to  most  anatomists,  of 
two  sets  of  muscular  fibres — viz.,  the  circular  and  the  radiating. 
The  circular  fibres,  which  are  much  the  most  abundant,  are  arranged 
in  concentric  lines  about  the  inner  edge  of  the  irjs,  near  the  pupil ; 
the  others  are  said  to  radiate  in  a  scattered  manner,  from  its  central 
parts  to  its  outer  margin.  The  action  of  these  two  sets  of  fibres  is 
to  contract  and  enlarge  tine  orifice  of  the  pupil.  The  circular  fibres, 
in  contracting,  draw  together  the  edges  of  the  pupil,  and  so  diminish 
its  opening ;  and  when  these  are  relaxed,  the  radiating  fibres  come 
into  play,  and  by  drawing  apart  the  edges  of  the  orifice,  enlarge 


SIGHT.  501 

the  pupillary  opening.  The  action  of  the  circular  fibres,  at  the 
same  time,  is  much  the  most  marked  and  important  of  the  two. 
For  when  the  whole  muscular  apparatus  of  the  eye  is  paralyzed 
by  the  action  of  belladonna,  or  by  the  division  of  the  third  pair  of 
nerves,  or  in  the  general  relaxation  of  the  muscular  system  at  the 
moment  of  death,  the  pupil  is  invariably  dilated,  probably  by  the 
passive  elasticity  of  its  tissues. 

During  life,  however,  these  different  conditions  of  the  pupil  cor- 
respond with  the  different  degrees  of  light  to  which  the  eye  is  ex- 
posed. In  a  strong  light,  the  pupil  contracts  and  shuts  out  the 
superfluous  rays ;  in  a  feeble  ligbt,  it  dilates,  in  order  to  collect 
into  the  eye  all  the  light  which  can  be  received  from  the  object. 
This  contractile  and  expansive  movement  of  the  pupil  is  a  rejiex 
action.  It  is  not  produced  by  the  direct  impression  of  the  light 
upon  the  iris  itself,  but  upon  the  retina;  since,  if  the  retina  be 
affected  with  complete  amaurosis,  or  if  the  light  be  entirely  shut  out 
from  it  by  an  opacity  of  the  lens,  no  such  effect  is  produced,  though 
the  iris  itself  be  exposed  to  the  direct  glare  of  day.  From  the 
retina  the  impression  is  transmitted,  through  the  optic  nerve,  to  the 
optic  tubercles  and  the  brain,  thence  reflected  outward  by  the  oculo- 
motorius  nerve  to  the  ophthalmic  ganglion,  and  so  through  the 
ciliary  nerves  to  the  iris. 

The  pupil  is  subject,  however,  to  various  other  nervous  influences 
beside  the  impressions  of  light  received  by  the  retina.  Thus  in 
poisoning  by  opium,  it  is  contracted  ;  in  coma  from  compression  of 
the  brain,  it  is  dilated ;  in  natural  sleep  it  is  contracted,  and  the  eye- 
ball rolled  upward  and  inward.  In  various  mental  conditions,  the 
pupil  is  also  enlarged  or  diminished,  and  thus  modifies  the  expres- 
sion of  the  eye;  and  in  viewing  remote  objects,  it  is  generally 
enlarged,  while,  in  looking  at  near  objects,  it  is  comparatively  con- 
tracted. But  still,  the  most  constant  and  important  function  be- 
longing to  the  iris  is  the  admission  or  exclusion  of  the  rays,  accord- 
ing to  the  intensity  of  the  light. 

Our  impressions  of  distance  and  solidity,  in  viewing  external 
objects,  are  produced  mainly  by  the  combined  action  of  the  two  eyes. 
For,  as  the  eyes  are  seated  a  certain  distance  apart  from  each  other 
in  the  head,  when  they  are  both  directed  toward  the  same  object, 
their  axes  meet  at  the  point  of  sight,  and  form  a  certain  angle  with 
each  other ;  and  this  angle  varies  with  the  distance  of  the  object. 
Thus,  when  the  object  is  within  a  short  distance,  the  axes  of  the 
two  eyes  will  necessarily  be  very  convergent,  and  the  angle  which 


602 


THE    SPECIAL    SENSES. 


they  form,  with  each  other  a  large  one ;  but  for  remote  objects,  the 
visual  axes  will  become  more  nearly  parallel,  and  their  angle  con- 
sequently smaller.  It  is  on  this  account  that  we  can  always  dis- 
tinguish whether  any  person  at  a  short  distance  is  looking  at  us, 
or  at  some  other  object  in  our  direction;  since  we  instinctively 
appreciate,  from  the  appearance  of  the  eyes,  whether  their  visual 
axes  meet  at  the  level  of  our  own  face. 

In  looking  at  a  landscape,  accordingly,  we  do  not  see  the  whole 
of  it  distinctly  at  the  same  moment,  but  only  those  parts  to  which 
out  attention  is  immediately  directed.  This  is  because,  in  the  first 
place,  the  focus  of  distinct  vision  varies,  in  each  eye,  for  different 
distances,  as  we  have  seen  in  a  former  paragraph,  and  secondly, 
because  both  eyes  can  only  be  directed  together,  at  one  time,  to 
objects  at  a  certain  distance.  Thus,  when  we  see  the  foreground 
or  the  middle  ground  distinctly,  the  distance  is  vague  and  uncer- 
tain, and  when  we  direct  our  eyes  more  particularly  to  the  horizon, 
objects  in  the  foreground  become  indistinct.  In  this  way  we  ap- 
preciate the  difference  in  distance  between  the  various  portions  of 
the  landscape,  as  a  whole.  In  the  case  of  particular  objects,  we  are 
assisted  also  by  the  alteration  in  their  individual  characters;  for 
distance  produces  a  diminution,  both  in  apparent  size  and  in  in- 
tensity of  color. 

The  combined  action  of  the  two  eyes  is  also  very  valuable,  for 
near  objects,  in  giving  us  an  idea  of  solidity  or  projection.  For 
within  a  certain  distance,  the  visual  axes  when  directed  together 


Fig.  163 


As  SEEN  BT  THE  LEFT  EYE. 


As  SEEN  BY  THE  RiGHT  EYE. 


at  a  solid  object,  are  so  convergent  that  the  two  eyes  do  not  receive 
the  same  image.      As  in  Figs.  163  and  164,  which  represent  a  skull 


SIGHT.  503 

as  seen  by  tlie  two  eyes,  when  placed  exactly  in  front  of  the  ob- 
server at  the  distance  of  eighteen  inches  or  two  feet,  the  right  eye 
will  see  the  object  partly  on  one  side,  and  the  left  eye  partly  on  the 
other.  And  by  the  union  or  combination  of  these  two  images  by 
the  visual  organs,  the  impression  of  solidity  is  produced. 

By  the  employment  of  double  pictures,  so  drawn  as  to  represent 
the  appearances  presented  to  the  two  eyes  by  the  same  object,  and 
so  arranged  that  each  shall  be  seen  only  by  the  corresponding  eye, 
a  deceptive  resemblance  may  be  produced  to  the  actual  appearance 
of  solid  objects.  This  is  accomplished  in  the  contrivance  known 
as  the  Stereoscope.  Thus,  if  two  pictures  similar  to  those  in  Figs, 
163  and  164  be  so  placed  that  one  shall  be  seen  only  with  the  right 
eye  and  the  other  only  with  the  left,  the  combination  of  the  two 
figures  will  take  place  as  if  they  came  from  the  real  object,  and 
all  the  natural  projections  will  come  out  in  relief. 

But  this  effect  is  produced  only  in  the  case  of  objects  situated 
within  a  moderately  short  distance.  For  very  remote  objects,  we 
lose  the  impression  of  solidity,  since  the  difference  in  the  images  on 
the  two  eyes  becomes  so  slight  as  to  be  inappreciable,  and  we  see 
only  a  plane  expanse  of  surface,  with  sharp  outlines  and  various 
shades  of  color,  but  no  actual  projections  or  depressions. 

The  sensibility  of  the  retina  is  such  that  it  cannot  distinguish 
luminous  points  which  are  received  upon  its  surface  at  a  very 
minute  distance  from  each  other.  In  this  particular,  the  sensibility 
of  the  retina  resembles  that  of  the  skin,  since  we  have  already 
found  that  the  integument  cannot  distinguish  the  impressions 
made  by  the  points  of  two  needles  placed  a  very  short  distance 
apart.  The  delicacy  of  this  discriminating  power,  in  the  retina,  is 
immeasurably  superior  to  that  of  the  skin;  and  yet  it  has  its 
limits,  even  in  the  nervous  expansion  of  the  eye.  For  if  we  look 
at  an  object  which  is  excessively  minute,  or  which  is  so  remote 
that  its  apparent  size  is  very  much  diminished,  we  lose  the  power 
of  distinguishing  its  different  parts,  and  can  no  longer  perceive 
its  real  outline.  This  is  a  very  different  condition  from  that  in 
which  the  confusion  of  vision  arises  from  defect  of  focusing  in  the 
eye,  as,  for  example,  in  long  or  short-sightedness,  or  where  the 
object  is  placed  too  near  the  eye  or  too  much  on  one  side.  For 
when  the  difficulty  depends  simply  on  its  minute  size  or  its  remote- 
ness, the  rays  coming  from  the  top  of  the  object  and  those  coming 
from  the  bottom,  are  all  brought  to  their  proper  focus  at  distinct 
points  on  the  retina — only  these  points  are  too  near  each  other  for  the 


504  THE    SPECIAL    SENSES. 

retina  to  distinguish  them  apart.  Consequently  we  can  no  longer 
appreciate  the  form  of  the  object. 

For  the  same  reason,  when  we  mix  together  minute  grains  of  a 
different  hue,  we  produce  an  intermediate  color.  If  yellow  and 
blue  be  mingled  in  this  way,  we  no  longer  perceive  the  separate 
blue  and  yellow  grains,  but  only  a  uniform  tinge  of  green;  and 
white  and  black  granules,  mixed  together,  produce,  at  a  short  dis- 
tance, the  appearance  of  a  continuous  shade  of  gray. 

Impressions,  once  produced  upon  the  retina,  remain  for  a  short  time 
afterward.  Usually  these  impressions  are  so  evanescent  after  the 
removal  of  their  immediate  cause,  and  are  so  soon  followed  by 
others  which  are  more  vivid,  that  we  do  not  notice  their  existence. 
They  may  very  readily  be  demonstrated,  however,  by  swinging 
rapidly  in  a  circle  before  the  eyes,  in  a  dark  room,  a  stick  lighted 
at  one  end.  As  soon  as  the  motion  has  attained  a  certain  degree  of 
velocity,  the  impression  produced  on  the  retina,  when  the  lighted 
end  of  the  stick  arrives  at  any  particular  spot,  remains  until  it  has 
completed  its  revolution  and  has  again  reached  the  same  point; 
so  that  the  effect  thus  produced  upon  the  eye  is  that  of  a  continu- 
ous circle  of  light.  The  same  fact  has  been  illustrated  by  the 
optical  contrivance,  known  as  the  Thaumatrope,  in  which  successive 
pictures  of  similar  figures  in  different  positions  are  made  to  revolve 
rapidly  before  the  eye,  and  thus  to  produce  the  apparent  effect  of  a 
single  figure  in  rapid  motion ; — since  the  eye  fails  to  perceive  the 
intervals  between  the  different  pictures. 

The  sense  of  vision,  therefore,  through  the  impressions  of  light, 
gives  us  ideas  of  form,  size,  color,  position,  distance,  and  movement. 
But  these  ideas  may  also  be  excited  by  impressions  derived  from 
an  internal  source,  as  well  as  those  produced  by  rays  coming  from 
without.  And  it  is  one  of  the  most  striking  peculiarities  of  the 
sense  of  sight  that  these  ideal  or  internal  impressions  which  are 
excited  in  it  by  various  causes,  are  much  more  vivid  and  powerful 
than  those  of  any  otJter  of  the  senses.  Thus,  in  a  dream,  we  often  see 
external  objects,  with  all  their  visible  peculiarities  of  light,  color 
form,  &c.,  nearly  or  quite  as  distinctly  as  when  we  are  awake ;  but 
the  imaginary  impressions  of  sound,  in  this  condition,  are  always 
comparatively  faint,  and  those  of  taste,  smell,  and  touch,  almost 
entirely  imperceptible.  Even  in  a  reverie,  in  the  waking  condi- 
tion, when  the  absorption  of  the  mind  in  its  own  thoughts  is  com- 
plete, and  we  are  withdrawn  altogether  from  outward  influences, 
we  see  objects  which  have  no  present  existence  as  if  they  were 


HEARING,  505 

actually  before  us.  It  is  this  sense  also  whicli  becomes  most  easily 
and  thoroughly  excited  in  certain  nervous  disorders ;  as,  for  exam- 
ple, in  delirium  tremens,  where  the  patient  often  sees  passing  before 
his  eyes  extensive  and  magnificent  landscapes,  crowds  of  human 
faces  and  figures,  and  series  of  towns  and  cities,  which  seem  to  be 
depicted  upon  the  imagination  with  a  force  and  distinctness,  much 
superior  to  that  of  other  delirious  impressions.  Since  the  sense  of 
sight,  therefore,  depends  less  directly  than  the  other  senses  upon 
the  actual  contact  of  material  objects,  it  is  also  more  easily  thrown 
into  activity  when  withdrawn  from  their  influence. 

Hearing. — The  sense  of  hearing  depends  upon  the  vibrations 
excited  in  the  atmosphere  by  sonorous  bodies,  which  are  themselves 
first  thrown  into  vibration  by  various  causes,  and  which  then  com- 
municate similar  undulations  to  the  surrounding  air.  These  sono- 
rous vibrations  are  of  such  a  character  that  they  cannot  be  directly 
appreciated  by  ordinary  sensibility,  but  the  result  of  numerous  and 
well-directed  physical  experiments  on  this  subject  leaves  no  doubt 
whatever  of  their  existence ;  and  when  such  vibrations  are  commu- 
nicated to  the  auditory  apparatus,  they  produce  in  it  the  sensation 
of  sound. 

In  the  case  of  the  aquatic  animals,  which  pass  their  entire  exist- 
ence beneath  the  surface  of  the  water,  the  water  itself,  which  is 
capable  of  vibrating  in  the  same  way,  communicates  the  sonorous 
impressions  to  the  organ  of  hearing;  but  in  terrestrial  animals, 
and  particularly  in  man,  it  is  the  atmosphere  which  always  serves 
as  the  medium  of  transmission. 

The  auditory  apparatus,  in  man  and  in  the  quadrupeds,  consists, 
first,  of  a  somewhat  expanded  and  trumpet-shaped  mouth,  or  ex- 
ternal ear,  destined  to  receive  and  collect  the  sonorous  impulses 
coming  from  various  quarters.  This  external  ear  is  constructed 
of  a  cartilaginous  framework,  covered  with  integument,  loosely 
attached  to  the  bones  of  tiae  head,  and  more  or  less  movable  by 
means  of  various  muscles,  which  by  their  contraction  turn  its 
expanded  orifice  in  different  directions.  In  man,  the  movements 
of  the  external  ear  are  almost  always  inappreciable,  though  the  mus- 
cles may  be  easily  demonstrated ;  but  in  many  of  the  lower  animals 
these  movements  are  exceedingly  varied  and  extensive,  and  play  a 
very  important  part  in  the  working  of  the  auditory  apparatus. 

At  the  bottom  of  the  external  ear,  its  orifice  is  prolonged  into  a 
tube  or  canal,  the  external  auditory  meatus,  partly  cartilaginous  and 


506  THE    SPECIAL    SENSES. 

partly  bony,  whicli  penetrates  the  lateral  part  of  the  temporal  bone 
in  a  nearly  horizontal  and  transverse  direction.  In  the  human 
subject,  this  canal  is  a  little  over  one  inch  in  length,  and  is  lined 
by  a  continuation  of  the  external  integument.  The  integument 
toward  its  outer  portion  is  beset  with  small  hairs,  and  provided 
with  ceruminous  glands  which  supply  a  secretion  of  a  waxy  or 
resinous  consistency.  By  these  means  the  passage  is  protected 
from  the  accidental  ingress  of  various  foreign  bodies. 

Secondly,  at  the  bottom  of  the  external  meatus  the  auditory  pas- 
sao^e  is  closed  by  a  thin  fibrous  membrane,  stretched  across  its  cavity, 
called  the  membrana  tympani.  Upon  this  membrane  are  received  the 
sonorous  vibrations  which  have  been  collected  by  the  external  ear 
and  conducted  inward  by  the  external  auditory  meatus.  Behind 
the  membrana  tympani  is  the  cavity  of  the  middle  ear,  or  the  cavity 
of  the  tympanum.  This  cavity  communicates  posteriorly  with  the 
mastoid  cells,  and  anteriorly  with  the  pharynx,  by  a  narrow  passage, 
lined  with  ciliated  epithelium,  and  running  downward,  forward  and 
inward,  called  the  Eustachian  tube.  A  chain  of  small  bones,  the 
malleus,  incus,  and  stapes,  is  stretched  across  the  cavity  of  the 
tympanum,  and  forms  a  communication  between  the  membrana 
tympani  on  the  outside,  and  the  membrane  closing  the  foramen 
ovale  in  the  petrous  portion  of  the  temporal  bone.  All  the  vibra- 
tions, accordingly,  which  are  received  by  the  membrana  tympani, 
are  transmitted  by  the  chain  of  bones  to  the  membrane  of  the 
foramen  ovale.  The  tension  of  the  membranes  is  regulated  by  two 
small  muscles,  the  tensor  tympani  and  stapedius  muscles,  which  arise 
from  the  bony  parts  in  the  neighborhood,  and  are  inserted  respect- 
ively into  the  neck  of  the  malleus  and  the  head  of  the  stapes,  and 
which  draw  these  bones  forward  and  backward  upon  their  articu- 
lations. 

Thirdly,  behind  the  membrane  of  the  foramen  ovale  lies  the 
labyrinth,  or  internal  ear.  This  consists  of  a  complicated  cavity, 
excavated  in  the  petrous  portion  of  the  temporal  bone,  and  com- 
prising an  ovoid  centrah  portion,  the  vestibule,  a  double  spiral  canal, 
the  cochlea,  and  three  semicircular  canals,  all  communicating  by 
means  of  the  common  vestibule.  All  parts  of  this  cavity  contain 
a  watery  fluid  termed  the  perilymph.  The  vestibule  and  semi- 
circular canals  also  contain  closed  membranous  sacs,  suspended  in 
the  fluid  of  the  perilymph,  which  reproduce  exactly  the  form  of 
the  bony  cavities  themselves,  and  communicate  with  each  other  in 
a  similar  way.     These  sacs  are  filled  with   another  watery  fluid, 


HEARING. 


507 


the  endolymph. ;  and  the  terminal  filaments  of  the  auditory  nerve 
are  distributed  upon  the  membranous  sac  of  the  vestibule  and  upon 
the  ampullae,  or  membranous  dilatations,  at  the  commencement  of 
the  three  semicircular  canals.  The  remaining  portion  of  the  audi- 
tory nerve  is  distributed  upon  the  septum  between  the  two  spiral 
canals  of  the  cochlea. 

Thus,  the  essential  or  fundamental  portion  of  the  auditory  appa- 
ratus is  evidently  the  internal  ear,  a  cavity,  partly  membranous  and 
partly  bony,  in  which  is  distributed  a  nerve  of  special  sense,  the 
auditory  nerve,  capable  of  appreciating  sonorous  impressions.  The 
accessory  parts,  on  the  other  hand,  are  the  chain  of  bones  and  the 
membrane  of  the  tympanum,  which  communicate  the  sonorous 
vibrations  directly  to  the  internal  ear ;  and  the  meatus  and  external 
ear,  which  collect  them  from  the  atmosphere.     The  reception  of 

Fig.  165. 


Human  Auditory 
rinth. 


Apparatus,  showing  external  auditory  meatus,  tyrapanum,  and  laby- 


sonorous  impulses  is  therefore  accomplished  in  a  very  indirect  way. 
For  the  sonorous  body  first  communicates  its  vibrations  to  the 
atmosphere.  By  the  atmosphere  these  vibrations  are  communicated 
to  the  membrana  tympani.  From  the  membrana  tympani,  they  are 
transmitted,  through  the  chain  of  bones,  to  the  membrane  of  the 
foramen  ovale;  thence  to  the  perilymph,  or  fluid  of  the  labyrinthic 
cavity,  and  from  the  perilymph  to  the  membranous  parts  of  the 
labyrinth  and  the  nerves  which  are  distributed  upon  them. 

The  arrangement  of  the  different  parts  composing  the  iynvpanum 
is  of  the  greatest  importance  for  the  perfect  enjoyment  of  the  sense 


508  THE    SPECIAL    SENSES. 

of  hearing.  For  the  air  on  the  two  sides  of  the  membrane  of  the 
tympanum  should  be  in  the  same  condition  of  elasticity  in  order  to 
allow  of  the  proper  vibration  of  the  membrane;  and  this  equilibrium 
would  be  liable  to  disturbance  if  the  air  within  the  tympanum  were 
completely  confined,  while  that  outside  is  subjected  to  variations 
of  barometric  pressure.  By  means  of  the  Eustachian  tube,  how- 
ever, a  communication  is  established  between  the  cavity  of  the 
tympanum  and  the  exterior,  and  the  free  vibration  of  the  membrane 
is  thus  secured. 

The  exact  tension  of  the  memhrana  tympani  itself  is  also  provided 
for,  as  we  have  already  observed,  by  the  action  of  the  two  muscles 
inserted  into  the  malleus  and  the  stapes.  By  the  contraction  of 
the  internal  muscle  of  the  malleus,  or  tensor  tympani,  the  membrane 
of  the  tympanum  is  drawn  inward  and  rendered  more  tense  than 
usual.  The  action  of  the  stapedius  muscle  is  by  some  thought  to 
relax  the  membrana  tympani,  by  others  to  assist  in  the  tension 
both  of  this  membrane  and  that  of  the  foramen  ovale,  to  which 
the  stapes  is  attached.  But  there  is  no  doubt  that  both  these  mus- 
cles, by  their  combined  or  alternate  action,  can  regulate  the  tension 
of  the  tympanic  membrane,  to  an  extraordinary  degree  of  nicety, 
and  thus  increase  the  ease  and  delicacy  with  which  various  sounds 
are  distinguished.  For  if  the  membrane  be  so  put  upon  the  stretch 
that  its  fundamental  note  shall  be  the  same  with  that  of  the  sound 
which  is  to  be  heard,  it  will  vibrate  more  readily  in  consonance 
with  the  undulations  of  the  atmosphere,  and  the  sound  will  be 
more  distinctly  heard.  On  the  contrary,  if  the  membrane  be  too 
highly  stretched,  very  grave  sounds  may  not  be  heard  at  all,  until 
its  tension  is  diminished  to  the  requisite  degree. 

Contrary  to  what  is  sometimes  asserted,  the  communication  of 
sonorous  impulses  to  the  internal  ear  is  accomplished  altogether  by 
means  of  the  tympanum  and  chain  of  bones.  It  has  been  thought  that 
sounds  were  transmitted,  in  many  instances,  directly  to  the  internal 
ear  by  the  medium  of  the  cranial  bones.  This  was  inferred  from 
such  facts  as  the  following.  If  a  tuning-fork,  in  vibration,  be  taken 
between  the  teeth,  its  sound  will  appear  very  much  louder  than 
if  it  were  simply  held  near  the  external  ear ;  and  if,  while  it  is  so 
held,  one  of  the  ears  be  closed,  the  sound  will  appear  very  much 
louder  on  that  side  than  on  the  other.  The  sound  will  also  be  heard 
if  the  tuning-fork  be  applied  to  the  upper  part  of  the  cranium  or 
the  mastoid  process,  with  a  similar  increase  of  resonance  on  closing 
the  ears.     Finally  our  own  voices  are  heard,  though  the  ears  be 


HEARING.  509 

both  closed,  and  the  sound  is  mucli  louder  with  the  ears  closed 
than  open. 

These  are  the  facts  which  have  led  to  the  belief  that,  in  such 
instances,  the  sound  was  communicated  directly  through  the  bones 
of  the  head,  vibrating  in  consonance  with  the  sounding  body.  But 
a  little  examination  will  show  that  such  is  not  the  case.  When  we 
hold  the  end  of  a  vibrating  tuning-fork  between  the  teeth,  we  no 
longer  hear  the  sound  in  the  vibrating  extremity  of  the  instrument 
or  its  neighborhood,  but  ^n  the  mouth  and  the  nasal  fossce.  It  is  the 
vibration  of  the  air  in  these  passages  which  produces  the  sound ; 
and  this  vibration  is  communicated  to  the  cavity  of  the  tympanum 
through  the  Eustachian  tube.  The  apparent  increase  of  sound,  also, 
on  closing  the  ears,  which  could  not  be  explained  on  the  supposition 
that  it  was  conducted  directly  through  the  bones  of  the  cranium, 
is  due  to  the  same  cause.  For  it  can  easily  be  seen,  on  trying  the 
experiment,  either  with  a  tuning-fork  held  between  the  teeth  or 
simply  with  our  own  voices,  that  this  apparent  increase  of  sound 
takes  place  only  when  the  ears  are  closed  by  gentle  pressure.  If  the 
pressure  be  excessive,  so  that  the  integument  is  forced  inward  into 
the  meatus  and  the  air  in  the  meatus  subjected  to  undue  compres- 
sion, the  sound  no  longer  appears  louder  in  the  corresponding  ear, 
and  may  even  be  lost  altogether. 

The  apparent  increase  of  sound,  therefore,  in  such  cases,  when 
the  ear  is  gently  closed,  is  due  to  the  fact  that  the  meatus  is  thus 
converted  into  a  reverberatory  cavity,  by  which  the  ^vibrations  of 
the  tympanum  are  increased  in  intensity.  But  if  the  air  in  the 
meatus  be  too  much  compressed  by  forcible  closure,  ^the  vibrations 
of  the  tympanum  are  then  interfered  with  and  the  sound  is  dimi- 
nished or  destroyed. 

In  all  cases,  then,  it  is  the  sonorous  vibrations  of  the  air  which 
produce  the  sound,  and  these  vibrations  are  recei-ved  invariably  by 
the  membrane  of  the  tympanum,  and  thence  transmitted  to  the 
internal  ear  by  the  chain  of  bones.  The  cranial  bones  are  incapable 
of  communicating  these  vibrations  to  the  labyrinth  and  its  contents, 
except  very  faintly  and  imperfectly.  For  common  experience  skows 
that  even  the  loudest  and  sharpest  sounds,  coming  from  without, 
are  almost  entirely  lost  on  closing  the  external  ears ;  and  our  own 
respiratory  and  cardiac  sounds,  which  are  so  easily  heard  as  soon 
as  the  chest  is  connected  with  the  ear  by  a  flexible  stethoscope,  are 
entirely  inaudible  to  us  in  the  usual  condition. 

The  exact  function  of  the  different  parts  of  the  internal  ear  is 


510  THE    SPECIAL    SEN-SES. 

not  well  understood.  It  has  been  thought  to  be  the  office  of  the 
semicircular  canals  to  determine  the  direction  from  which  the  sono- 
rous impulses  are  propagated.  This  opinion  was  based  upon  the 
curious  fact  that  these  canals,  always  three  in  number,  are  placed 
in  such  positions  as  to  correspond  with  the  three  different  directions 
of  vertical  height,  lateral  extension,  and  longitudinal  extension; 
for  one  of  them  is  nearly  vertical  and  transverse,  another  vertical 
and  longitudinal,  and  the  third  horizontal  in  position.  The  sono- 
rous impulses,  therefore,  coming  in  either  of  these  directions,  would 
be  received  by  only  one  of  the  semicircular  canals  (by  direct  con- 
duction through  the  bones  of  the  head)  perpendicularly  to  its  own 
plane;  and  an  intermediate  direction,  it  was  thought,  might  be 
appreciated  by  the  combined  effect  of  the  impulse  upon  two  adja- 
cent canals. 

Enough  has  already  been  said,  however,  in  regard  to  the  com- 
munication of  sound  directly  through  the  bones  of  the  head  to  the 
internal  ear,  to  show  that  this  cannot  be  the  way  in  which  the  direc- 
tion of  sound  is  ascertained.  Indeed,  when  we  hear  any  loud  and 
well-marked  sound  coming  from  a  particular  region,  such  as  the 
music  of  a  military  band  or  the  whistle  of  a  locomotive,  we  have  only 
to  close  the  external  ears  to  lose  our  perception  both  of  the  sound 
and  its  direction.  The  direction  of  sonorous  impressions  is  appre- 
ciated in  a  different  way.  In  the  first  place,  we  feel  that  the  sound 
comes  from  one  side  or  the  other,  by  its  making  a  more  distinct 
impression  on  one  ear  than  the  opposite;  and  by  inclining  the 
head  slightly  in  various  directions,  we  easily  ascertain  whether  the 
sound  becomes  more  or  less  acute,  and  so  judge  of  its  actual  source. 
Many  of  the  lower  animals,  whose  ears  are  very  large  and  movable, 
use  this  method  to  great  extent.  A  horse,  for  example,  when  upon 
the  road,  often  keeps  his  ears  in  constant  motion,  feeling,  as  it  were, 
in  the  distance,  for  the  origin  of  the  various  sounds  which  excite 
his  attention. 

Beside  the  above,  we  are  further  assisted  in  our  judgment  of  the 
direction  of  sounds  by  our  previous  knowledge  of  the  localities, 
the  direction  of  the  wind,  and  the  manner  in  which  the  sound  is 
reflected  by  surrounding  objects.  When  these  sources  of  informa- 
tion fail  us,  we  are  often  at  a  loss.  It  is  notoriously  difficult,  for 
example,  to  judge  of  the  place  of  the  chirping  of  a  cricket  in  a 
perfectly  closed  room,  or  of  the  direction  of  a  bell  heard  on  the 
water  in  a  thick  fog. 

The  sense  of  hearing  has  a  much  closer  analogy  with  ordinary 


ON    THE    SENSES   IN    GENERAL.  511 

sensibility  than  that  of  sight.  Thus,  in  the  first  place,  hearing  is 
accomplished  by  the  direct  intervention  and  contact  of  a  material 
body — the  atmosphere ;  for  sonorous  impulses  cannot  be  produced 
in  a  vacuum,  and  we  hear  no  sound  from  a  bell  rung  under  an 
exhausted  receiver.  Secondly,  the  nature  of  the  impressions  pro- 
duced by  sound  is  such  that  we  can  often  describe  them  by  the 
same  terms  which  are  applied  to  ordinary  sensations.  Thus,  we 
speak  of  sounds  as  sharp  and  dull,  piercing,  smooth,  or  rough ;  and 
we  feel  the  impulse  of  a  sudden  and  violent  explosive  sound,  like 
that  of  a  blow  upon  the  tympanum. 

By  this  sense,  therefore,  we  distinguish  the  quality,  intensity, 
pitch,  duration,  and  direction  of  sonorous  impulses.  The  delicacy 
with  which  these  distinctions  are  appreciated  varies  considerably 
in  different  individuals  ;  and  in  different  kinds  of  animals  there  is 
reason  to  believe  that  the  diversity  is  much  greater,  some  of  them 
being  almost  insensible  to  sounds  which  are  readily  perceived  by 
others.  In  man,  the  number  and  variety  of  tones  which  can  usually 
be  discriminated  is  very  great ;  and  this  sense,  accordingly,  in  the 
complication  and  finish  of  its  apparatus,  and  the  perfection  and  deli- 
cacy of  its  action,  must  be  regarded  as  second  only  to  that  of  vision. 

On  the  Senses  in  General. — There  are  several  facts  connected 
with  the  operation  of  the  senses,  both  general  and  special,  which 
are  common  to  all  of  them,  and  which  still  remain  to  be  considered. 
In  the  first  place,  an  impression  of  any  kind,  made  upon  a  sensi- 
tive organ,  remains  for  a  time  after  the  removal  of  its  exciting  cause. 
We  have  already  noticed  this  in  regard  to  the  senses  of  taste,  smell, 
and  sight,  but  it  is  equally  true  of  the  hearing  and  the  touch. 
Thus,  if  the  skin  be  touched  with  a  piece  of  ice,  the  acute  sensa=- 
tion  remains  for  a  few  seconds,  whether  the  ice  be  removed  or  not. 
For  the  higher  order  of  the  special  senses,  the  time  during  which 
this  secondary  impression  remains  is  a  shorter  one.  In  the  case  of 
hearing,  however,  it  has  been  measured  with  a  tolerable  approach 
to  accuracy ;  for  it  has  been  found  that,  if  the  sonorous  undulations 
follow  each  other  with  a  greater  rapidity  than  sixteen  times  per 
second,  they  become  fused  together  into  a  continuous  sound,  pro- 
ducing upon  the  ear  the  impression  of  a  musical  note.  The  varying 
pitch  of  the  note  depends  upon  the  rapidity  with  which  the  vibra- 
tions succeed  each  other.  When  the  succession  of  vibrations  is 
vary  rapid,  a  high  note  is  the  result,  and  when  comparatively  slow, 
a  low  note  is  produced ;  but  when  the  number  of  impulses  falls 


512  THE    SPECIAL    SENSES. 

below  sixteen  per  second,  we  then  begin  to  perceive  the  distinct 
vibrations,  and  so  lose  the  impression  of  a  continuous  note. 

All  the  senses,  in  the  second  place,  become  accustomed  to  a  con- 
tinued impression,  so  that  they  no  longer  perceive  its  existence. 
Thus,  if  a  perfectly  uniform  pressure  be  exerted  upon  any  part  of 
the  body,  the  compressing  substance  after  a  time  fails  to  excite  any 
sensation  in  the  skin,  and  we  remain  unconscious  of  its  existence. 
In  order  to  attract  our  notice,  it  is  then  necessary  to  increase  or 
diminish  the  pressure ;  while,  so  long  as  this  remains  uniform,  no 
effect  is  perceived.  But  if,  after  the  skin  has  thus  become  accus- 
tomed to  its  presence,  the  foreign  body  be  suddenly  removed,  our 
attention  is  then  immediately  excited,  and  we  notice  the  absence  of 
an  impression,  in  the  same  way  as  if  it  were  a  positive  sensation. 

We  all  know  how  rapidly  we  become  habituated  to  odors,  whether 
agreeable  or  disagreeable  in  their  nature,  in  the  confined  air  of  a 
close  apartment;  although,  on  first  entering  from  without  our 
attention  may  have  been  attracted  by  them  in  a  very  decided 
manner.  A  continuous  and  uniform  sound,  also,  like  the  steady 
rumbling  of  carriages,  or  the  monotonous  hissing  of  boiling  water, 
becomes  after  a  time  inaudible  to  us;  but  as  soon  as  the  sound 
ceases,  we  notice  the  alteration,  and  our  attention  is  at  once  excited. 
The  senses,  accordingly,  receive  their  stimulus  more  from  the  varia- 
tions and  contrasts  of  external  impressions,  than  from  these  impres- 
sions themselves. 

Another  important  particular,  in  regard  to  the  senses,  is  their 
capacity  for  education.  The  proofs  of  this  are  too  common  and  too 
apparent  to  need  more  than  a  simple  allusion.  The  touch  may  be 
so  trained  that  the  blind  may  read  words  and  sentences  by  its  aid, 
in  raised  letters,  where  an  ordinary  observer  would  hardly  detect 
anything  more  than  a  barely  distinguishable  inequality  of  surface. 
The  educated  eye  of  the  artist,  or  the  naturalist,  will  distinguish 
variations  of  color,  size,  and  outline,  altogether  inappreciable  to 
ordinary  vision ;  and  the  senses  of  taste  and  smell,  in  those  who  are 
in  the  habit  of  examining  wines  and  perfumes,  acquire  a  similar 
superiority  of  discriminating  power. 

In  these  instances,  however,  it  is  not  probable  that  the  organ  of 
sense  itself  becomes  any  more  perfect  in  organization,  or  more 
susceptible  to  sensitive  impressions.  The  increased  functional 
power,  developed  by  cultivation,  depends  rather  upon  the  greater 
delicacy  of  the  perceptive  and  discriminative  faculties.  It  is  a  mental 
and  not  a  physical  superiority  which   gives  the  painter  or  the 


ON    THE    SENSES    IN    GENERAL.  613 

naturalist  a  greater  power  of  distinguishing  colors  and  outlines, 
and  which  enables  the  physician  to  detect  nice  variations  of  quality 
in  the  sounds  of  the  heart  or  the  respiratory  murmur  of  the  lungs. 
The  impressions  of  external  objects,  therefore,  in  order  to  produce 
their  complete  effect,  must  first  be  received  by  a  sensitive  appa- 
ratus, which  is  perfect  in  organization  and  functional  activity; 
and,  secondly,  these  impressions  must  be  subjected  to  the  action  of 
an  intelligent  perception,  by  which  their  nature,  source  and  rela- 
tions may  be  fully  appreciated. 

That  part  of  the  nervous  system  which  we  have  hitherto 
studied,  viz.,  the  cerebro-spinal  system,  consists  of  an  apparatus  of 
nerves  and  ganglia,  destined  to  bring  the  individual  into  relation 
with  the  external  world.  By  means  of  the  special  senses,  he  is 
made  cognizant  of  sights,  sounds,  taste,  and  odors,  by  which  he 
is  attracted  or  repelled,  and  which  guide  him  in  the  pursuit  and 
choice  of  food.  By  the  general  sensations  of  touch  and  the  volun- 
tary movements,  he  is  enabled  to  alter  at  will  his  position  and 
location,  and  to  adapt  them  to  the  varying  conditions  under  which 
he  may  be  placed.  The  great  passages  of  entrance  into  the  body, 
and  of  exit  from  it,  are  guarded  by  the  same  portion  of  the  nerv- 
ous system.  The  introduction  of  food  into  the  mouth,  and  its 
passage  through  the  oesophagus  to  the  stomach,  are  regulated  by 
the  same  nervous  apparatus ;  and  even  the  passage  of  air  through 
the  larynx,  and  its  penetration  into  the  lungs,  are  equally  under 
the  guidance  of  sensitive  and  motor  nerves  belonging  to  the 
cerebro-spinal  system. 

It  will  be  observed  that  the  above  functions  relate  altogether 
either  to  external  phenomena  or  to  the  simple  introduction  into  the 
body  of  food  and  air,  which  are  destined  to  undergo  nutritive 
changes  in  the  interior  of  the  frame. 

If  we  examine,  however,  the  deeper  regions  of  the  body,  we  find 
located  in  them  a  series  of  internal  phenomena,  relating  only  to 
the  substances  and  materials  which  have  already  penetrated  into 
the  frame,  and  which  form  or  are  forming  a  part  of  its  structure. 
These  are  the  purely  vegetative  functions,  as  they  are  called ;  or 
those  of  growth,  nutrition,  secretion,  excretion,  and  reproduction. 
These  functions,  and  the  organs  to  which  they  belong,  are  not 
under  the  direct  influence  of  the  cerebro-spinal  nerves,  but  are 
regulated  by  another  portion  of  the  nervous  system,  viz.,  the 
"  ganglionic  system ;"  or,  as  it  is  more  commonly  called,  the  "  sys- 
tem of  the  great  sympathetic." 
33 


514:  SYSTEM    OF    THE    GREAT    SYMPATHETIC. 


CHAPTER    VII. 

SYSTEM   OF   THE   GREAT   SYMPATHETIC. 

The  sympathetic  system  consists  of  a  double  chain  of  nervous 
ganglia,  running  from  the  anterior  to  the  posterior  extremity  of  the 
body,  along  the  front  and  sides  of  the  spinal  column,  and  connected 
with  each  other  by  slender  longitudinal  filaments.  Each  ganglion 
is  reinforced  by  a  motor  and  sensitive  filament  derived  from  the 
cerebro-spinal  system,  and  thus  the  organs  under  its  influence  are 
brought  indirectly  into  communication  with  external  objects  and 
phenomena.  The  nerves  of  the  great  sympathetic  are  distributed 
to  organs  over  which  the  consciousness  and  the  will  have  no  imme- 
diate control,  as  the  intestine,  kidneys,  heart,  liver,  &c. 

The  first  sympathetic  ganglion  in  the  head  is  the  ophthalmic  gan- 
glion. This  ganglion  is  situated  within  the  orbit  of  the  eye,  on  the 
outer  aspect  of  the  optic  nerve.  It  communicates  by  slender  fila- 
ments with  the  carotid  plexus,  which  forms  the  continuation  of  the 
sympathetic  system  from  below ;  and  receives  a  motor  root  from 
the  oculo-motorius  nerve,  and  a  sensitive  root  from  the  ophthalmic 
branch  of  the  fifth  pair.  Its  filaments  of  distribution,  known  as  the 
"  ciliary  nerves,"  pass  forward  upon  the  eyeball,  pierce  the  sclerotic, 
and  finally  terminate  in  the  iris. 

The  next  division  of  the  great  sympathetic  in  the  head  is  the 
spheno-palatine  ganglion,  situated  in  the  spheno-maxillary  fossa.  It 
communicates,  like  the  preceding,  with  the  carotid  plexus,  and 
receives  a  motor  root  from  the  facial  nerve,  and  a  sensitive  root 
from  the  superior  maxillary  branch  of  the  fifth  pair.  Its  filaments 
are  distributed  to  the  levator  palati  and  azygos  uvulee  muscles,  and 
to  the  mucous  membrane  about  the  posterior  nares. 

The  third  sympathetic  ganglion  in  the  head  is  the  submaxillary, 
situated  upon  the  submaxillary  gland.  It  communicates  with  the 
superior  cervical  ganglion  of  the  sympathetic  by  filaments  which 
accompany  the  facial  and  external  carotid  arteries.  It  derives  its 
sensitive  filaments  from  the  lingual  branch  of  the  fifth  pair,  and  its 


SYSTEM    OF    THE    GREAT    SYMPATHETIC. 


515 


motor  filaments  from  the  facial  nerve,  by  means  of  the  chorda 
tympani.  Its  branches  of  distribution  pass  to  the  sides  of  the  tongue 
and  to  the  submaxillary  and  sublingual  glands. 

The  last  sympathetic  ganglion  in  the  head  is  the  otic  ganglion. 
It  is  situated  just  beneath  the 

base  of  the  skull,  on  the  inner  Fig.  166. 

side  of  the  third  division  of 
the  fifth  pair.  It  sends  fila- 
ments of  communication  to 
the  carotid  plexus;  and  re- 
ceives a  motor  root  from  the 
facial  nerve,  and  a  sensitive 
root  from  the  inferior  maxil- 
lary division  of  the  fifth  pair. 
Its  branches  are  sent  to  the 
internal  muscle  of  the  mal- 
leus in  the  middle  ear  (tensor 
tympani),  and  to  the  mucous 
membrane  of  the  tympanum 
and  Eustachian  tube. 

The  continuation  of  the 
sympathetic  nerve  in  the  neck 
consists  of  two  and  some- 
times three  ganglia,  the  su- 
perior, middle,  and  inferior. 
These  ganglia  communicate 
with  each  other,  and  also 
with  the  anterior  branches 
of  the  cervical  spinal  nerves. 
Their  filaments  follow  the 
course  of  the  carotid  artery 
and  its  branches,  covering 
them  with  a  network  of  inter- 
lacing fibres,  and  are  finally 
distributed  to  the  substance  of 
the  thyroid  gland,  and  to  the 
walls  of  the  larynx,  trachea, 
pharynx,     and     oesophagus. 

By  the  superior,  middle,  and  inferior  cardiac  nerves,  they  also  supply 
sympathetic  fibres  to  the  cardiac  plexuses  and  to  the  substance  of 
the  heart. 


Course  and  distribution  of  the  Gkeat 

THETIC. 


516  SYSTEM    OF    THE    GliEAT   SYMPATHETIC. 

In  the  chest,  the  ganglia  of  the  sympathetic  nerve  are  situated  on 
each  side  the  spinal  column,  just  over  the  heads  of  the  ribs,  with 
which  they  accordingly  correspond  in  number.  Their  communi- 
cations with  the  intercostal  nerves  are  double ;  each  sympathetic 
ganglion  receiving  two  filaments  from  the  intercostal  nerve  next 
above  it.  The  filaments  originating  from  the  thoracic  ganglia  are 
distributed  upon  the  thoracic  aorta,  and  to  the  lungs  and  oesophagus. 

In  the  abdomen,  the  continuation  of  the  sympathetic  system  con- 
sists principally  of  the  aggregation  of  ganglionic  enlargements 
situated  upon  the  coeliac  artery,  known  as  the  semilunar  or  cceliac 
ganglion.  From  this  ganglion  a  multitude  of  radiating  and  inoscu- 
lating branches  are  sent  out,  which,  from  their  diverging  course  and 
their  common  origin  from  a  central  mass,  are  termed  the  "  solar 
plexus."  From  this,  other  diverging  plexuses  originate,  which 
accompany  the  abdominal  aorta  and  its  branches,  and  are  distri- 
buted to  the  stomach,  small  and  large  intestine,  spleen,  pancreas, 
liver,  kidneys,  supra-renal  capsules,  and  internal  organs  of  gene- 
ration. 

Beside  the  above  ganglia  there  are  in  the  abdomen  four  other 
pairs,  situated  in  front  of  the  lumbar  vertebrae,  and  having  similar 
connections  with  those  occupying  the  cavity  of  the  chest.  Their 
filaments  join  the  plexuses  radiating  from  the  semilunar  ganglion. 

In  the  pelvis,  the  sympathetic  system  is  continued  by  four  or  five 
pairs  of  ganglia,  situated  on  the  anterior  aspect  of  the  sacrum,  and 
terminating,  at  the  lower  extremity  of  the  spinal  column,  in  a  single 
ganglion,  the  "  ganglion  impar,"  which  is  probably  to  be  regarded 
as  a  fusion  of  two  separate  ganglia. 

The  entire  sympathetic  series  is  in  this  way  composed  of  nume- 
rous small  ganglia  which  are  connected  throughout,  first,  with  each 
other ;  secondly,  with  the  cerebro-spinal  system ;  and  thirdly,  with 
the  internal  viscera  of  the  body. 

The  properties  and  functions  of  the  great  sympathetic  have  been 
less  successfully  studied  than  those  of  the  cerebro-spinal  system, 
owing  to  the  anatomical  difficulties  in  the  way  of  reaching  and 
operating  upon  this  nerve  for  purposes  of  experiment.  The  cerebro- 
spinal axis  and  its  nerves  are  easily  exposed  and  subjected  to  exami- 
nation. It  is  also  easy  to  isolate  particular  portions  of  this  system, 
and  to  appreciate  the  disturbances  of  sensation  and  motion  conse- 
quent upon  local  lesions  or  irritations.  The  phenomena,  further- 
more, which  result  from  experiments  upon  this  part  of  the  nervous 
apparatus,  are  promptly  produced,  are  well-marked  in  character, 


SYSTEM    OF    THE    GREAT    SYMPATHETIC.  517 

and  are,  as  a  general  rule,  readily  understood  by  the  experimenter. 
On  the  other  hand,  the  principal  part  of  the  sympathetic  system  is 
situated  in  the  interior  of  the  chest  and  abdomen ;  and  the  mere 
operation  of  opening  these  cavities,  so  as  to  reach  the  ganglionic 
centres,  causes  such  a  disturbance  in  the  functions  of  vital  organs, 
and  such  a  shock  to  the  system  at  large,  that  the  results  of  these 
experiments  have  been  always  more  or  less  confused  and  unsatis- 
factory. Furthermore,  the  connections  of  the  sympathetic  ganglia 
with  each  other  and  with  the  cerebro-spinal  axis  are  so  numerous 
and  so  scattered,  that  these  ganglia  cannot  be  completely  isolated 
without  resorting  to  an  operation  still  more  mutilating  and  injuri- 
ous in  its  character.  And  finally,  the  sensible  phenomena  which 
are  obtained  by  experimenting  on  the  great  sympathetic  are,  in 
the  majority  of  cases,  slow  in  making  their  appearance,  and  not 
particularly  striking  or  characteristic  in  their  nature. 

Notwithstanding  these  difficulties,  however,  some  facts  have  been 
ascertained  with  regard  to  this  part  of  the  nervous  system,  which 
give  us  a  certain  degree  of  insight  into  its  character  and  functions. 

The  great  sympathetic  is  endowed  both  with  sensibility  and  the 
power  of  exciting  motion;  but  these  properties  are  less  active 
here  than  in  the  cerebro-spinal  system,  and  are  exercised  in  a  dif- 
ferent manner.  If  we  irritate,  for  example,  a  sensitive  nerve  in 
one  of  the  extremities,  or  apply  the  galvanic  current  to  the  poste- 
rior root  of  a  spinal  nerve,  the  evidences  of  pain  or  of  reflex 
action  are  acute  and  instantaneous.  There  is  no  appreciable  inter- 
val between  the  application  of  the  stimulus  and  the  sensations 
which  result  from  it.  On  the  other  hand,  experimenters  who  have 
operated  upon  the  sympathetic  ganglia  and  nerves  of  the  chest  and 
abdomen  find  that  evidences  of  sensibility  are  distinctly  manifested 
here  also,  but  much  less  acutely,  and  only  after  somewhat  prolonged 
application  of  the  irritating  cause.  These  results  correspond  very 
closely  with  what  we  know  of  the  vital  properties  of  the  organs 
which  are  supplied  either  principally  or  exclusively  by  the  sym- 
pathetic; as  the  liver,  intestine,  kidneys,  &c.  These  organs  are 
insensible,  or  nearly  so,  to  ordinary  impressions.  We  are  not  con- 
scious of  the  changes  and  operations  going  on  in  them,  so  long  as 
these  changes  and  operations  retain  their  normal  character.  But 
they  are  still  capable  of  perceiving  unusual  or  excessive  irritations, 
and  may  even  become  exceedingly  painful  when  in  a  state  of  in- 
flammation. 

There  is  the  same  peculiar  character  in  the  action  of  the  motor 


518  SYSTEM    OF    THE    GREAT    SYMPATHETIC. 

nerves  belonging  to  the  sympathetic  system.  If  the  facial  or  hypo- 
glossal, or  the  anterior  root  of  a  spinal  nerve  be  irritated,  the  con- 
vulsive movement  which  follows  is  instantaneous,  violent,  and  only 
momentary  in  its  duration.  But  if  the  semilunar  ganglion  or  its 
nerves  be  subjected  to  a  similar  experiment,  no  immediate  effect  is 
produced.  It  is  only  after  a  few  seconds  that  a  slow,  vermicular, 
progressive  contraction  takes  place  in  the  corresponding  part  of  the 
intestine,  which  continues  for  some  time  after  the  exciting  cause 
has  been  removed. 

Morbid  changes  taking  place  in  organs  supplied  by  the  sympa- 
thetic present  a  similar  peculiarity  in  the  mode  of  their  produc- 
tion. If  the  body  be  exposed  to  cold  and  dampness,  for  example, 
congestion  of  the  kidneys  shows  itself  perhaps  on  the  following 
day.  Inflammation  of  any  of  the  internal  organs  is  very  rarely 
established  within  twelve  or  twenty -four  hours  after  the  application 
of  the  exciting  cause.  The  internal  processes  of  nutrition,  together 
with  their  derangements,  which  are  regarded  as  especially  under 
the  control  of  the  great  sympathetic,  always  require  a  longer  time 
to  be  influenced  by  incidental  causes,  than  those  which  are  regulated 
by  the  nerves  and  ganglia  of  the  cerebro-spinal  system. 

In  the  head,  the  sympathetic  has  a  close  and  important  connec- 
tion with  the  exercise  of  the  special  senses.  This  is  illustrated 
more  particularly  in  the  case  of  the  eye,  by  its  influence  over  the 
alternate  expansion  and  contraction  of  the  pupil.  The  ophthalmic 
ganglion  sends  off  a  number  of  ciliary  nerves,  which  are  distributed 
to  the  iris.  It  is  connected,  as  we  have  seen,  with  the  remaining 
sympathetic  ganglia  in  the  head,  and  receives,  beside,  a  sensitive 
root  from  the  ophthalmic  branch  of  the  fifth  pair,  and  a  motor  root 
from  the  oculo-motorius.  The  reflex  action  by  which  the  pupil 
contracts  under  a  strong  light  falling  upon  the  retina,  and  expands 
under  a  diminution  of  light,  takes  place,  accordingly,  through  this 
ganglion.  The  impression  conveyed  by  the  optic  nerve  to  the 
tubercula  quadrigemina,  and  reflected  outward  by  the  fibres  of 
the  oculo-motorius,  is  not  transmitted  directly  by  the  last  named 
nerve  to  the  iris ;  but  passes  first  to  the  ophthalmic  ganglion,  and 
is  thence  conveyed  to  its  destination  by  the  ciliary  nerves. 

The  reflex  movements  of  the  iris  exhibit  consequently  a  some- 
what sluggish  character,  which  indicates  the  intervention  of  a  part 
of  the  sympathetic  system.  The  changes  in  the  size  of  the  pupil 
do  not  take  place  instantaneously,  with  the  variation  in  the  amount 
of  light,  but  always  require  an  appreciable  interval  of  time.     If 


SYSTEM    OF    THE    GREAT    SYMPATHETIC.  519 

we  pass  suddenly  from  a  brilliantly  lighted  apartment  into  a  dark 
room,  we  are  unable  to  distinguish  surrounding  objects  until  a 
certain  time  has  elapsed,  and  the  expansion  of  the  pupil  has  taken 
place ;  and  vision  even  continues  to  grow  more  and  more  distinct 
for  a  considerable  period  afterward,  as  the  expansion  of  the  pupil 
becomes  more  complete.  Again,  if  we  cover  the  eyes  of  another 
person  with  the  hand  or  a  folded  cloth,  and  then  suddenly  expose 
them  to  the  light,  we  shall  find  that  the  pupil,  which  is  at  first 
dilated,  contracts  somewhat  rapidly  to  a  certain  extent,  and  after- 
ward continues  to  diminish  in  size  during  several  seconds,  until  the 
proper  equilibrium  is  fairly  established.  Furthermore,  if  we  pass 
suddenly  from  a  dark  room  into  the  bright  sunshine,  we  are  imme- 
diately conscious  of  a  painful  sensation  in  the  eye,  which  lasts  for 
a  considerable  time ;  and  which  results  from  the  inability  of  the 
pupil  to  contract  with  sufficient  rapidity  to  shut  out  the  excessive 
amount  of  light.  All  such  exposures  should  be  made  gradually, 
so  that  the  movements  of  the  iris  may  keep  pace  with  the  varying 
quantity  of  stimulus,  and  so  protect  the  eye  from  injurious  impres- 
sions. 

The  reflex  movements  of  the  iris,  however,  though  accomplished 
through  the  medium  of  the  ophthalmic  ganglion,  derive  their 
original  stimulus,  through  the  motor  root  of  this  ganglion,  from 
the  oculo-motorius  nerve.  For  it  has  been  found  that  if  the  oculo- 
motorius  nerve  be  divided  between  the  brain  and  the  eyeball,  the 
pupil  becomes  immediately  dilated,  and  will  no  longer  contract 
under  the  influence  of  light.  The  motive  power  originally  derived 
from  the  brain  is,  therefore,  in  the  case  of  the  iris,  modified  by 
passing  through  one  of  the  sympathetic  ganglia  before  it  reaches 
its  final  destination. 

An  extremely  interesting  fact  in  this  connection  is  the  following. 
Of  the  three  organs  of  special  sense  in  the  head,  viz.,  the  eye,  the 
nose,  and  the  ear,  each  one  is  provided  with  two  sets  of  muscles, 
superficial  and  deep,  which  together  regulate  the  quantity  of  stimu- 
lus admitted  to  the  organ,  and  the  mode  in  which  it  is  received. 
The  superficial  set  of  these  muscles  is  animated  by  branches  of  the 
facial  nerve ;  the  deep-seated  or  internal  set,  by  filaments  from  a 
sympathetic  ganglion. 

Thus,  the  front  of  the  eyeball  is  protected  by  the  orbicularis  and 
levator  palpebrse  superioris  muscles,  which  open  or  close  the  eye- 
lids at  will,  and  allow  a  larger  or  smaller  quantity  of  light  to  reach 
the  cornea.     These  muscles  are  supplied  by  the  oculo-motorius  and 


520  SYSTEM    OP    THE    GREAT    SYMPATHETIC. 

facial  nerves,  and  are  for  the  most  part  voluntary  in  their  action. 
The  iris,  on  the  other  hand,  is  a  more  deeply-seated  muscular 
curtain,  which  regulates  the  quantity  of  light  admitted  through  the 
pupil.  There  is  also  the  ciliary  muscle,  which  regulates  the  position 
of  the  crystalline  lens,  and  secures  a  correct  focusing  of  the  light, 
at  different  distances.  Both  these  muscles  are  supplied,  as  we  have 
seen,  by  filaments  from  the  ophthalmic  ganglion,  and  their  move- 
ments are  involuntary  in  character. 

In  the  olfactory  apparatus,  the  anterior  or  superficial  set  of 
muscles  are  the  compressors  and  elevators  of  the  alae  nasi,  which 
are  animated  by  filaments  of  the  facial  nerve.  By  their  action, 
odoriferous  vapors,  when  faint  and  delicate  in  their  character,  are 
snuffed  up  and  directed  into  the  upper  part  of  the  nasal  passages, 
where  they  come  in  contact  with  the  most  sensitive  portions  of  the 
olfactory  membrane ;  or,  if  too  pungent  or  disagreeable  in  flavor, 
are  excluded  from  entrance.  These  muscles  are  not  very  im- 
portant or  active  in  the  human  subject ;  but  in  many  of  the  lower 
animals  with  a  more  active  and  powerful  sense  of  smell,  as,  for 
example,  the  carnivora,  they  may  be  seen  to  play  a  very  important 
part  in  the  mechanism  of  olfaction.  Furthermore,  the  levators  and 
depressors  of  the  velum  palati,  which  are  more  deeply  situated, 
serve  to  open  or  close  the  orifice  of  the  posterior  nares,  and  accom- 
plish a  similar  office  with  the  muscles  already  named  in  front.  The 
levator  palati  and  azygos  uvulas  muscles,  which,  by  their  action, 
tend  to  close  the  posterior  nares,  are  supplied  by  filaments  from  the 
spheno-palatine  ganglion,  and  are  involuntary  in  their  character. 

The  ear  has  two  similar  sets  of  muscles,  similarly  supplied.  The 
first,  or  superficial  set,  are  those  moving  the  external  ear,  viz.,  the 
anterior,  superior,  and  posterior  auriculares.  Like  the  muscles  of 
the  anterior  nares,  they  are  comparatiYely  inactive  in  man,  but  in 
many  of  the  lower  animals  are  well  developed  and  important.  In 
the  horse,  the  deer,  the  sheep,  &c.,  they  turn  the  ear  in  various 
directions  so  as  to  catch  more  distinctly  faint  and  distant  sounds,  or 
to  exclude  those  which  are  harsh  and  disagreeable.  These  muscles 
are  supplied  by  filaments  of  the  facial  nerve,  and  are  voluntary  in 
their  action. 

The  deep-seated  set  are  the  muscles  of  the  middle  ear.  In  order 
to  understand  their  action,  we  must  recollect  that  sounds  are  trans- 
mitted from  the  external  to  the  middle  ear  through  the  membrane 
of  the  tympanum,  which  vibrates,  like  the  head  of  a  drum,  on 
receiving  sonorous  impulses  from  without. 


^  SYSTEM    OF    THE    GREAT    SYMPATHETIC.  521 

The  membraae  of  the  tympanum,  accordingly,  which  is  an  elastic 
sheet,  stretched  across  the  passage  to  the  internal  ear,  may  be  made 
more  or  less  sensitive  to  sonorous  impressions  by  varying  its  con- 
dition of  tension  or  relaxation.  This  condition  is  regulated,  as  we 
have  already  seen,  by  the  combined  action  of  the  two  muscles  of 
the  middle  ear,  viz.,  the  tensor  tympani  and  the  stapedius.  The 
first  named  muscle,  the  action  of  which  is  perfectly  well  understood, 
is  supplied  with  nervous  filaments  from  the  otic  ganglion  of  the 
sympathetic.  By  its  contraction,  the  handle  of  the  malleus  is  drawn 
inward,  bringing  the  membrana  tympani  with  it,  and  putting  this 
membrane  upon  the  stretch.  On  the  relaxation  of  the  muscle,  the 
chain  of  bones  returns  to  its  ordinary  position,  by  the  elasticity  of 
the  neighboring  parts,  and  the  previous  condition  of  the  tympanic 
membrane  is  restored.  This  action,  so  far  as  we  can  judge,  is  purely 
involuntary.  But  the  stapedius  muscle  is  separately  supplied  by  a 
minute  branch  of  the  facial  nerve.  It  is  probable  that  this  arrange- 
ment enables  us  to  make  also  a  certain  degree  of  voluntary  exer- 
tion, in  listening  intently  for  faint  or  distant  sounds. 

In  all  these  instances,  the  reflex  action  taking  place  in  the 
deeper  seated  muscles,  originates  from  a  sensation  which  is  con- 
veyed inward  to  the  cerebro-spinal  centres,  and  is  then  transmitted 
outward  to  its  final  destination  through  the  medium  of  one  of  the 
sympathetic  ganglia. 

Another  very  striking  fact,  concerning  the  sympathetic,  relates  to 
the  changes  produced  by  its  division,  in  the  nutritive  processes  of 
the  parts  supplied  by  it.  One  of  the  most  important  and  remark- 
able of  these  changes  is  an  elevation  of  temperature  in  the  affectel 
parts.  If  the  sympathetic  nerve  be  divided  on  one  side  of  the  neck, 
in  the  rabbit,  cat,  or  dog,  an  elevation  of  temperature  begins  to  be 
perceptible  on  the  corresponding  side  of  the  head  in  a  very  shoii 
time.  In  the  cat,  we  have  found  a  very  sensible  difference  in 
temperature  between  the  two  sides  at  the  end  of  ten  minutes; 
and  in  the  rabbit,  at  the  end  of  half  an  hour.  A  vascular  conges- 
tion of  the  parts  also  takes  place,  which  may  be  seen  to  great 
advantage  in  the  ear  of  the  rabbit,  when  held  up  between  the  eye 
and  the  light.  The  elevation  of  temperature,  in  these  cases,  is  very 
perceptible  to  the  touch,  and  may  also  be  measured  by  the  thermo- 
meter. Bernard*  has  found  it  to  reach  8°  or  9°  F.  The  elevation 
of  temperature  and  congested  state  of  the  parts  are  sometimes  found 
to  be  diminished  by  the  next  day,  and  afterward  disappear  rapidly. 
'  Eecherches  Experimentales  sur  le  Grand  Sympathique.     Paris,  1854. 


522 


SYSTEM    OF    THE    GREAT    SYMPATHETIC. 


Occasionally,  however,  they  last  for  a  long  time.  Bernard  {op.  cit.) 
has  seen  the  unnatural  temperature  of  the  affected  parts  remain,  in 
the  rabbit,  from  fifteen  to  eighteen  days,  and  in  the  dog  for  two 
months.  Where  the  superior  cervical  ganglion  has  been  extirpated, 
he  has  even  found  the  above  appearances  to  continue,  in  the  dog,  for 
a  year  and  a  half.  They  may  also,  according  to  the  same  authority, 
be  reproduced  several  times  in  the  same  animal,  by  repeated  divi- 
sions of  the  sympathetic  nerve. 

The  above  effect  is  due  to  a  peculiar  modification  in  the  nutri- 
tion of  the  affected  parts,  which  has  some  analogy  with  inflamma- 
tion. The  unnatural  heat,  the  congestion,  and  the  increased  sensi- 
bility which  are  present,  all  serve  to  indicate  a  certain  resemblance 
between  the  two  conditions.  None  of  the  more  serious  consequences 
of  inflammation,  however,  such  as  oedema,  exudation,  sloughing  or 
ulceration,  have  ever  been  known  to  follow  from  this  operation ; 
and  the  term  inflammation,  accordingly,  cannot  properly  be  applied 
to  its  results. 

Division  of  the  sympathetic  nerve  in  the  middle  of  the  neck 
has  also  a  very  singular  and  instantaneous  effect  on  the  muscular 
apparatus  of  the  eye.  "Within  a  very  few  seconds  after  the  above 
operation  has  been  performed  upon  the  cat,  the  pupil  of  the  cor- 
responding eye  becomes  strongly  contracted,  and  remains  in  that 
condition.  At  the  same  time  the  third  eyelid,  or  "  nictitating  mem- 
brane," with  which  these  animals 
Fig.  167.  are  provided,  is  drawn  partially 

over  the  cornea,  and  the  upper 
and  lower  eyelids  also  approxi- 
mate very  considerably  to  each 
other;  so  that  all  the  apertures 
guarding  the  eyeball  are  very 
perceptibly  narrowed,  and  the  ex- 
pression of  the  face  on  that  side  is 
altered  in  a  corresponding  degree. 
This  effect  upon  the  pupil  has 
been  explained  by  supposing  the 
circular  fibres  of  the  iris,  or  the 
constrictors  of  the  pupil,  to  be 
animated  exclusively  by  nervous  filaments  derived  from  the  oculo- 
motorius ;  and  the  radiating  fibres,  or  the  dilators,  to  be  supplied 
by  the  sympathetic.  Accordingly,  while  division  of  the  oculo- 
raotorius  would  produce  dilatation  of  the  pupil,  by  paralysis  of 


Cat,  aftei  section  of  the  right  sympathetic. 


SYSTEM    OF    THE    GREAT    SYMPATHETIC,  523 

the  circular  fibres  only,  division  of  the  sympathetic  would  be 
followed  by  exclusive  paralysis  of  the  dilators,  and  a  permanent 
contraction  of  the  pupil  would  consequently  take  place.  The 
above  explanation,  however,  is  not  a  satisfactory  one;  since,  in 
the  first  place,  division  of  the  oculo-motorius,  as  the  experiments  of 
Bernard  have  shown,^  does  not  by  itself  produce  complete  dilata- 
tion of  the  pupil ;  and,  secondly,  after  division  of  the  sympathetic 
nerve  in  the  cat,  as  we  have  already  shown,  not  only  is  the  pupil 
contracted,  but  both  the  upper  and  lower  eyelids  and  the  nictitating 
membrane  are  also  partially  drawn  over  the  cornea,  and  assist  in 
excluding  the  light.  The  last-named  effect  cannot  be  owing  to  anv 
direct  paralysis,  from  division  of  the  fibres  of  the  sympathetic.  It 
is  more  probable  that  the  section  of  this  nerve  operates  simply  by 
exaggerating  for  a  time  the  sensibility  of  the  retina,  as  it  does  that 
of  the  integument ;  and  that  the  partial  closure  of  the  eyelids  and 
pupil  is  a  secondary  consequence  of  that  condition. 

It  will  be  remembered  that  in  describing  the  inflammation  of  the 
eyeball,  consequent  upon  section  of  the  fifth  pair  of  nerves,  we 
found  that  there  were  reasons  for  believing  this  effect  to  be  due 
to  injury  of  certain  sympathetic  fibres  which  accompany  the  fifth 
pair.  If  the  fifth  pair  in  fact  be  divided  at  the  level  of  the  Cas- 
serian  ganglion,  where  it  is  joined  by  sympathetic  fibres  from  the 
carotid  plexus,  or  between  this  ganglion  and  the  eyeball,  a  destruc- 
tive inflammation  of  the  organ  follows.  But  if  the  section  be  made 
behind  the  ganglion,  so  as  to  avoid  the  filaments  of  communication 
with  the  sympathetic,  no  inflammatory  change  takes  place.  If  this 
fact  be  really  owing  to  the  presence  of  sympathetic  fibres  which 
accompany  the  fifth  pair,  it  indicates  a  remarkable  difference  in  the 
effects  of  dividing  the  sympathetic  near  the  eyeball  and  at  a  dis- 
tance from  it;  since  no  real  inflammation  of  the  eyeball  or  its 
appendages  is  ever  produced  by  division  of  this  nerve  in  the  middle 
of  the  neck,  but  only  the  elevation  of  temperature  and  increase  of 
sensibility  which  have  been  already  described. 

The  influence  of  the  sympathetic  nerve  and  the  consequences 
of  its  division  upon  the  thoracic  and  abdominal  viscera  have  been 
only  very  imperfectly  investigated  by  experimental  methods.  It 
undoubtedly  serves  as  a  medium  of  reflex  action  between  the  sensi- 
tive and  motor  portions  of  the  digestive,  excretory,  and  generative 

'  Lf^(;ons  8ur  la  Physiologie  et  la  Pathologie  du  Systeme  Nerveux,  Paris,  1858, 
vol.  ii   p.  203. 


52-i  SYSTEM    OF    THE    GREAT    SYMPATHETIC. 

apparatuses ;  and  it  is  certain  that  it  also  takes  part  in  reflex  actions 
in  which  the  cerebro-spinal  system  is  at  the  same  time  interested. 
There  are  accordingly  three  different  kinds  of  reflex  action,  taking 
place  wholly  or  partially  through  the  sympathetic  system,  which 
may  be  observed  to  occur  in  the  living  body. 

1st.  Reflex  actions  taking  place  from  the  internal  organs,  through 
the  sympathetic  and  cerebrospinal  system.s,  to  the  voluntary  muscles  and 
sensitive  surfaces. — The  convulsions  of  young  children  are  often 
owing  to  the  irritation  of  undigested  food  in  the  intestinal  canal. 
Attacks  of  indigestion  are  also  known  to  produce  temporary  amau- 
rosis, double  vision,  strabismus,  and  even  hemiplegia.  Nausea,  and 
a  diminished  or  capricious  appetite,  are  often  prominent  symptoms 
of  early  pregnancy,  induced  by  the  peculiar  condition  of  the  uterine 
mucous  membrane. 

2d.  Reflex  actions  taking  place  from  the  sensitive  surfaces,  through 
the  cerebro-spinal  and  sympathetic  systems,  to  the  involuntary  muscles 
and  secreting  organs. — Imprudent  exposure  of  the  integument  to 
cold  and  wet,  will  often  bring  on  a  diarrhoea.  Mental  and  moral 
impressions,  conveyed  through  the  special  senses,  will  affect  the 
motions  of  the  heart,  and  disturb  the  processes  of  digestion  and 
secretion.  Terror,  or  an  absorbing  interest  of  any  kind,  will  pro- 
duce a  dilatation  of  the  pupil,  and  communicate  in  this  way  a  pecu- 
liarly wild  and  unusual  expression  to  the  eye.  Disagreeable  sights 
or  odors,  or  even  unpleasant  occurrences,  are  capable  of  hastening 
or  arresting  the  menstrual  discharge,  or  of  inducing  premature 
delivery. 

3d.  Reflex  actions  taking  place  through  the  sympathetic  system,  from 
one  part  of  the  internal  organs  to  another. — The  contact  of  food  with 
the  mucous  membrane  of  the  small  intestine  excites  a  peristaltic 
movement  in  the  muscular  coat.  The  mutual  action  of  the  diges- 
tive, urinary  and  internal  generative  organs  upon  each  other  takes 
place  through  the  medium  of  the  sympathetic  ganglia  and  their 
nerves.  The  variations  of  the  capillary  circulation  in  different 
abdominal  viscera,  corresponding  with  the  state  of  activity  or  re- 
pose of  their  associated  organs,  are  to  be  referred  to  a  similar  nerv- 
ous influence.  These  phenomena  are  not  accompanied  by  any 
consciousness  on  the  part  of  the  individual,  nor  by  any  apparent 
intervention  of  the  cerebro-spinal  system. 


SECTION  III. 
REPRODUCTION. 


CHAPTEK    I. 


ON   THE   NATURE   OF   REPRODUCTION,   AND   THE 
ORIGIN    OF    PLANTS    AND    ANIMALS. 

The  process  of  reproduction  is  the  most  characteristic,  and  in 
many  respects  the  most  interesting,  of  all  the  phenomena  presented 
by  organized  bodies.  It  includes  the  whole  history  of  the  changes 
taking  place  in  the  organs  and  functions  of  the  individual  at  suc- 
cessive periods  of  life,  as  well  as  the  production,  growth,  and  de- 
velopment of  the  new  germs  which  make  their  appearance  by 
generation. 

For  all  organized  bodies  pass  through  certain  well-defined  epochs 
or  phases  of  development,  by  which  their  structure  and  functions 
undergo  successive  alterations.  We  have  already  seen  that  the 
living  animal  or  plant  is  distinguished  from  inanimate  substances 
by  the  incessant  changes  of  nutrition  and  growth  which  take  place 
in  its  tissues.  The  muscles  and  the  mucous  membranes,  the  osse- 
ous and  cartilaginous  tissues,  the  secreting  and  circulatory  organs, 
all  incessantly  absorb  oxygen  and  nutritious  material  from  with- 
out, and  assimilate  their  molecules ;  while  new  substances,  produced 
by  a  retrogressive  alteration  and  decomposition,  are  at  the  same 
time  excreted  and  discharged.  These  nutritive  changes  correspond 
in  rapidity  with  the  activity  of  the  other  vital  phenomena ;  since 
the  production  of  these  phenomena,  and  the  very  existence  of  the 
vital  functions,  depend  upon  the  regular  and  normal  continuance 
of  the  nutritive  process.  Thus  the  organs  and  tissues,  which  are 
always  the  seat  of  this  double  change  of  renovation  and  decay, 

(  525  ) 


526  NATURE    OF    REPRODUCTION. 

retain  nevertlieless  their  original  constitution,  and  continue  to  be 
capable  of  exhibiting  the  vital  phenomena. 

The  above  changes,  however,  are  not  in  reality  the  only  ones 
which  take  place.  For  although  the  structure  of  the  body  and  the 
composition  of  its  constituent  parts  appear  to  be  maintained  in  an 
unaltered  condition,  by  the  nutritive  process,  from  one  moment  to 
another,  or  from  day  to  day,  yet  a  comparative  examination  of 
them  at  greater  intervals  of  time  will  show  that  this  is  not  pre- 
cisely the  case ;  but  that  the  changes  of  nutrition  are,  in  point  of 
fact,  progressive  as  well  as  momentary.  The  composition  and  pro- 
perties of  the  skeleton,  for  example,  are  not  the  same  at  the  age  of 
twenty-five  that  they  were  at  fifteen.  At  the  later  period  it  con- 
tains more  calcareous  and  less  organic  matter  than  before ;  and  its 
solidity  is  accordingly  increased,  while  its  elasticity  is  diminished. 
Even  the  anatomy  of  the  bones  alters  in  an  equally  gradual  manner ; 
the  medullary  cavities  enlarging  with  the  progress  of  growth,  and 
the  cancellated  tissue  becoming  more  open  and  spongy  in  texture. 
"We  have  already  noticed  the  difference  in  the  quantity  of  oxygen 
and  carbonic  acid  inspired  and  exhaled  at  different  ages.  The 
muscles,  also,  if  examined  after  the  lapse  of  some  years,  are  found 
to  be  less  irritable  than  formerly,  owing  to  a  slow,  but  steady  and 
permanent  deviation  in  their  intimate  constitution. 

The  vital  properties  of  the  organs,  therefore,  change  with  their 
varying  structure ;  and  a  time  comes  at  last  when  they  are  per- 
ceptibly less  capable  of  performing  their  original  functions  than 
before.  This  alteration,  being  dependent  on  the  varying  activity 
of  the  nutritive  process,  continues  necessarily  to  increase.  The  very 
exercise  of  the  vital  powers  is  inseparably  connected  with  the  sub- 
sequent alteration  of  the  organs  employed  in  them ;  and  the  func- 
tions of  life,  therefore,  instead  of  remaining  indefinitely  the  same, 
pass  through  a  series  of  successive  changes,  which  finally  terminate 
in  their  complete  cessation. 

The  history  of  a  living  animal  or  plant  is,  therefore,  a  history  of 
successive  epochs  or  phases  of  existence,  in  each  of  which  the  struc- 
ture and  functions  of  the  body  differ  more  or  less  from  those  in 
every  other.  Every  living  being  has  a  definite  term  of  life,  through 
which  it  passes  by  the  operation  of  an  invariable  law,  and  which, 
at  some  regularly  appointed  time,  comes  to  an  end.  The  plant 
germinates,  grows,  blossoms,  bears  fruit,  withers,  and  decays.  The 
animal  is  born,  nourished,  and  brought  to  maturity,  after  which  he 
retrogrades  and  dies.     The  very  commencement  of  existence,  by 


NATURE    OF    RKPEODUCTION.  527 

leading  through,  its  successive  intermediate  stages,  conducts  at  last 
necessarily  to  its  own  termination. 

But  while  individual  organisms  are  thus  constantly  perishing  and 
disappearing  from  the  stage,  the  particular  kind,  or  species,  remains 
in  existence,  apparently  without  any  important  change  in  the  cha- 
racter or  appearance  of  the  organized  forms  belonging  to  it.  The 
horse  and  the  ox,  the  oak  and  the  pine,  the  different  kinds  of  wild 
and  domesticated  animals,  even  the  different  races  of  man  himself, 
have  remained  without  any  essential  alteration  ever  since  the  earliest 
historical  epochs.  Yet  during  this  period  innumerable  individuals, 
belonging  to  each  species  or  race,  must  have  lived  through  their 
natural  term  and  successively  passed  out  of  existence.  A  species 
may  therefore  be  regarded  as  a  type  or  class  of  organized  beings,  in 
which  the  particular  forms  or  structures  composing  it  die  off  con- 
stantly and  disappear,  but  which  nevertheless  repeats  itself  from 
year  to  year,  and  maintains  its  ranks  constantly  full  by  the  regular 
accession  of  new  individuals.  This  process,  by  which  new  organ- 
isms make  their  appearance,  to  take  the  place  of  those  which  are 
destroyed,  is  known  as  the  process  of  reproduction  or  generation.  Let 
us  now  see  in  what  manner  it  is  accomplished. 

It  has  always  been  known  that,  as  a  general  rule  in  the  process 
of  generation,  the  young  animals  or  plants  are  produced  directly 
from  the  bodies  of  the  elder.  The  relation  between  the  two  is  that 
of  parents  and  progeny;  and  the  new  organisms,  thus  generated, 
become  in  turn  the  parents  of  others  which  succeed  them.  For  this 
reason  wherever  such  plants  or  animals  exist,  they  indicate  the 
previous  existence  of  others  belonging  to  the  same  species ;  and  if 
by  any  accident  the  whole  species  should  be  destroyed  in  any  par- 
ticular locality,  no  new  individuals  could  be  produced  there,  unless 
by  the  previous  importation  of  others  of  the  same  kind. 

The  commonest  observation  shows  this  to  be  true  in  regard  to 
those  animals  and  plants  with  whose  history  we  are  more  familiarly 
acquainted.  An  opinion,  however,  has  sometimes  been  maintained 
that  there  are  exceptions  to  this  rule ;  and  that  living  beings  may, 
under  certain  circumstances,  be  produced  from  inanimate  substances, 
without  any  similar  plants  or  animals  having  preceded  them ;  pre- 
senting, accordingly,  the  singular  phenomenon  of  a  progeny  without 
parents.  Such  a  production  of  organized  bodies  is  known  by  the 
name  of  spontaneous  generation.  It  is  believed  by  the  large  majority 
of  physiologists  at  the  present  day  that  no  such  spontaneous  gene- 
ration ever  takes  place ;  but  that  plants  and  animals  are  always 


528  NATURE    OF    REPRODUCTION". 

derived,  by  direct  reproduction,  from  previously  existing  parents 
of  the  same  species.  As  this,  however,  is  a  question  of  some  im- 
portance, and  one  which  has  been  frequently  discussed  in  works  on 
physiology,  we  shall  proceed  to  pass  in  review  the  facts  which  have 
been  adduced  in  favor  of  the  occurrence  of  spontaneous  generation, 
as  well  as  those  which  would  lead  to  its  disproval  and  rejection. 

It  is  evident,  in  the  first  place,  that  many  apparent  instances  of 
spontaneous  generation  are  found  to  be  of  a  very  different  character 
as  soon  as  they  are  subjected  to  a  critical  examination.  Thus  grass- 
hoppers and  beetles,  earthworms  and  crayfish,  the  swarms  of  minute 
insects  that  fill  the  air  over  the  surface  of  stagnant  pools,  and  even 
frogs,  moles,  and  lizards,  have  been  supposed  in  former  times  to  be 
generated  directly  from  the  earth  or  the  atmosphere ;  and  it  was 
only  by  investigating  carefully  the  natural  history  of  these  animals 
that  they  were  ascertained  to  be  produced  in  the  ordinary  manner 
by  generation  from  parents,  and  were  found  to  continue  the  repro- 
duction of  their  species  in  the  same  way.  A  still  more  striking 
instance  is  furnished  by  the  production  of  maggots  in  putrefying 
meat,  vegetables,  flour  paste,  fermenting  dung,  &c.  If  a  piece  of 
meat  be  exposed,  for  example,  and  allowed  to  undergo  the  process 
of  putrefaction,  at  the  end  of  a  few  days  it  will  be  found  to  contain 
a  multitude  of  living  maggots  which  feed  upon  the  decomposing 
flesh.  Now  these  maggots  are  always  produced  under  the  same 
conditions  of  warmth,  moisture  and  exposure,  and  at  the  same  stage 
of  the  putrefactive  process.  They  are  never  to  be  found  in  fresh 
meat,  nor,  in  fact,  in  any  other  situation  than  the  one  just  mentioned. 
They  appear,  consequently,  without  any  similar  individuals  having 
existed  in  the  same  locality ;  and  considering  the  regularity  of  their 
appearance  under  the  given  conditions,  and  their  absence  elsewhere, 
it  has  been  believed  that  they  were  spontaneously  generated,  under 
the  influence  of  warmth,  moisture,  and  the  atmosphere,  from  the 
decaying  organic  substances. 

A  little  examination,  however,  discovers  a  very  simple  solution 
of  the  foregoing  difficulty.  On  watching  the  exposed  animal  or 
vegetable  substances  during  the  earlier  periods  of  their  decompo- 
sition, it  is  found  that  certain  species  of  flies,  attracted  by  the  odor 
of  the  decaying  material,  hover  round  it  and  deposit  their  eggs 
upon  its  surface  or  in  its  interior.  These  eggs,  hatched  by  the 
warmth  to  which  they  are  exposed,  produce  the  maggots ;  which 
are  simply  the  young  of  the  winged  insects,  and  which  after  a  time 
become  transformed,  by  the  natural  progress  of  development,  into 


INFUSORIAL    ANIMALCULES.  529 

perfect  insects  similar  to  their  parents.  The  difficulty  of  account- 
ing for  the  presence  of  the  maggots  by  generation,  therefore,  de- 
pends simply  on  the  fact  that  they  are  different  in  appearance  from 
the  parents  that  produce  them.  This  difference,  however,  is  merely 
a  temporary  one,  corresponding  with  the  difference  in  age,  and  dis- 
appears when  the  development  of  the  animal  is  complete;  just  as 
the  young  chicken,  when  recently  hatched,  has  a  different  form  and 
plumage  from  those  which  it  presents  in  its  adult  condition. 

Nearly  all  the  causes  of  error,  in  fact,  which  have  suggested  at 
various  times  the  doctrine  of  spontaneous  generation,  have  been 
derived  from  these  two  sources.  First,  tlie  ready  transportation  of 
eggs  or  germs,  and  their  rapid  hatching  under  favorable  circum- 
stances ;  and  secondly,  the  different  appearances  presented  by  the 
same  animal  at  different  ages,  in  consequence  of  which  the  youthful 
animal  may  be  mistaken,  by  an  ignorant  observer,  for  an  entirely 
different  species.  These  sources  of  error  are,  however,  so  readily 
detected,  as  a  general  rule,  by  scientific  investigation,  that  it  is 
hardly  necessary  to  point  out  the  particular  instances  in  which  they 
exist.  In  fact,  whenever  a  rare  or  comparatively  unknown  animal 
or  plant  has  been  at  any  time  supposed  to  be  produced  by  sponta- 
neous generation,  it  has  only  been  necessary,  for  the  most  part,  to 
investigate  thoroughly  its  habits  and  functions,  to  discover  its  secret 
methods  of  propagation,  and  to  show  that  they  correspond,  in  all 
essential  particulars,  with  the  ordinary  laws  of  reproduction.  The 
limits,  therefore,  within  which  the  doctrine  of  spontaneous  genera- 
tion can  be  applied,  have  been  narrowed  in  precisely  the  same 
degree  that  the  study  of  natural  history  and  comparative  physiology 
has  advanced.  At  present,  indeed,  there  remain  but  two  classes 
of  phenomena  which  are  ever  supposed  to  lend  any  support  to  the 
above  doctrine ;  viz.,  the  existence  and  production,  1st,  of  infuso- 
rial animalcules,  and  2d,  of  animal  and  vegetable  parasites.  "We 
shall  now  proceed  to  examine  these  two  parts  of  the  subject  in 
succession. 

Infusorial  Animalcules. — If  water,  holding  in  solution  or- 
ganic substances,  be  exposed  to  the  contact  of  the  atmosphere  at 
ordinary  temperatures,  it  is  found  after  a  short  time  to  be  filled 
with  swarms  of  minute  living  organisms,  which  are  visible  only  by 
the  microscope.  The  forms  of  these  microscopic  animalcules  are 
exceedingly  varied ;  owing  either  to  the  great  number  of  species 
in  existence,  or  to  their  rapid  alteration  during  the  successive  pe- 
U 


530 


NATURE    OF    REPRODUCTION. 


Different  kiuds  of  I.nf0sokia. 


riods  of  their  growth.  Ehrenberg  has  described  more  than  300 
different  varieties  of  them.  They  are  generally  provided  with  cilia 
attached  to  the  exterior  of  their  bodies,  and  are,  for  the  most  part, 
in  constant   and   rapid   motion   in  the  fluid  which  they  inhabit. 

Owing   to  their   presence  in 
^^"       '  '  animal  and  vegetable  watery 

infusions,  they  have  received 
the  name  of  "infusoria,"  or 
"  infusorial  animalcules." 

Now  these  infusoria  are 
always  produced  under  the 
conditions  which  we  have  de- 
scribed above.  The  animal 
or  vegetable  substance  used 
for  the  infusion  may  be  pre- 
viously baked  or  boiled,  so 
as  to  destroy  all  living  germs 
which  it  might  accidentally 
contain;  the  water  in  which 
it  is  infused  may  be  carefully 
distilled,  and  thus  freed  from  all  similar  contamination;  and  yet  the 
infusorial  animalcules  will  make  their  appearance  at  the  usual  time 
and  in  the  usual  abundance.  It  is  only  requisite  that  the  infusion 
be  exposed  to  a  moderately  elevated  temperature,  and  to  the  access 
of  atmospheric  air;  conditions  which  are  equally  necessary  for 
maintaining  the  life  of  all  animal  and  vegetable  organisms,  what- 
ever be  the  source  from  which  they  are  derived.  Under  the  above 
circumstances,  therefore,  either  the  animalcules  must  have  been 
produced  by  spontaneous  generation  in  the  watery  infusion,  or  their 
germs  must  have  been  introduced  into  it  through  the  medium  of 
the  atmosphere.  No  such  introduction  has  ever  been  directly  de- 
monstrated, nor  have  even  any  eggs  or  germs  belonging  to  the 
infusoria  ever  been  detected. 

Nevertheless,  there  is  every  probability  that  the  infusoria  are 
produced  from  germs,  and  not  by  spontaneous  generation.  Since 
the  infusoria  themselves  are  microscopic  in  size,  it  is  not  surprising 
that  their  eggs,  which  must  be  smaller  still,  should  have  escaped 
observation.  We  know,  too,  that  in  many  instances  the  minute 
germs  of  animals  or  plants  may  be  wafted  about  in  a  dry  state  by 
the  atmosphere,  until,  by  accidentally  coming  in  contact  with  warmth 
and  moisture,  they  become  developed  and  bring  forth  living  organ- 


INFUSORIAL    ANIMALCULES.  531 

isms.  The  eggs  of  the  infusoria,  accordingly,  may  be  easily  raised 
and  held  suspended  in  the  atmosphere,  under  the  form  of  minute 
dust-like  particles,  ready  to  germinate  and  become  developed  when- 
ever they  are  caught  by  the  surface  of  a  stagnant  pool,  or  of  any 
artificially  prepared  infusion.  In  point  of  fact,  the  atmosphere 
does  really  contain  an  abundance  of  such  dust-like  particles,  even 
when  it  appears  to  be  most  transparent  and  free  from  impurities. 
This  may  be  readily  demonstrated  by  admitting  a  single  beam  of 
sunshine  into  a  darkened  apartment,  when  the  shining  particles  sus- 
pended in  the  atmosphere  become  immediately  visible  in  the  track 
of  the  sunbeam.  Again,  if  a  perfectly  clean  and  polished  mirror 
be  placed  with  its  face  upward  in  a  securely  closed  room,  and  left 
undisturbed  for  several  days,  its  surface  at  the  end  of  that  time  will 
be  found  to  be  dimmed  by  the  settling  upon  it  of  minute  dust, 
deposited  from  the  atmosphere.  There  is  no  reason,  therefore,  for 
disbelieving  that  the  air  may  always  contain  a  sufficient  number  of 
organic  germs  for  the  production  of  infusorial  animalcules. 

There  is  some  difficulty,  however,  in  obtaining  direct  proof  that  it 
is  through  the  medium  of  the  atmosphere  that  organic  germs  pene- 
trate into  the  watery  infusions.  It  is  true  that  if  such  an  infusion 
be  prepared  from  baked  meat  or  vegetables  and  distilled  water,  and 
afterward  hermetically  sealed,  no  infusoria  are  developed  in  it ;  but 
this  only  shows,  as  we  have  already  intimated,  that  the  free  access 
of  air  is  necessary  to  the  development  of  all  organic  life,  just  as  it  is 
to  the  support  of  animals  and  plants  under  ordinary  conditions  of 
growth  and  reproduction.  Such  a  result,  therefore,  proves  nothing 
with  regard  to  the  external  origin  of  the  infusoria.  In  order  to  be 
conclusive,  such  an  experiment  should  be  so  contrived  that  the 
watery  infusion,  previously  freed  from  all  foreign  contamination, 
should  be  supplied  with  a  free  access  of  atmospheric  air,  while  the 
introduction  of  living  germs  by  this  channel  should  at  the  same  time 
be  rendered  impossible.  An  experiment  of  this  kind  has  in  reality 
been  contrived  and  successfully  carried  out  by  Schultze,  of  Berlin.' 

This  observer  prepared  an  infusion  containing  organic  substances 
in  solution,  and  inclosed  it  in  a  glass  flask  (Fig.  169,  a)  of  such  a 
size,  that  the  infusion  filled  about  one-half  the  entire  capacity  of  the 
vessel.  The  mouth  of  the  flask  was  fitted  with  an  air-tight  stopper 
provided  with  two  holes,  through  which  were  passed  narrow  glass 
tubes  bent  at  right  angles.     To  each  of  these  tubes  was  attached  a 

'  Edinburgh  New  Philosophical  .Tonriial,  Oct.  1837. 


532 


NATURE    OF    REPRODUCTION. 


Fig.  169. 


Schnltze's  experimeDt  on  Sponta- 
neous Generation. — a.  Flask  con- 
taining watery  infusion.  6.  Potash-ap- 
paratas  containing  sulphuric  acid.  e. 
Potash-apparatus  containing  caustic  po- 
tassa. 


potash-apparatus  {h,  c),  similar  to  those  used  for  condensing  carbonic 
acid  in  organic  analyses.  One  of  these  {b)  was  filled  with  concen- 
trated sulphuric  acid,  the  other  (c)  with  a  solution  of  caustic  potassa. 

The  flask  with  the  organic  infusion 
having  been  subjected  to  a  boiling 
temperature,  in  order  to  destroy  any 
living  germs  which  it  might  con- 
tain, the  stopper  was  inserted,  and 
the  whole  apparatus  exposed  to  the 
light,  at  the  ordinary  summer  tempera- 
ture. The  connections  of  the  apparatus 
being  perfectly  tight,  no  air  could  pene- 
trate into  the  flask,  except  by  passing 
through  either  the  sulphuric  acid  or 
the  potassa;  either  of  which  would 
retain  and  destroy  any  organic  germs 
which  might  be  suspended  in  it.  Every 
day  a  fresh  supply  of  air  was  introduced 
into  the  flask  by  drawing  it  through 
the  tubes  b,  c;  and  in  this  way  the  atmospheric  air  above  the  infu- 
sion was  constantly  renewed,  while  at  the  same  time  the  introduction 
of  living  germs  from  without  was  effectually  prevented. 

Schultze  kept  this  apparatus  under  his  observation,  as  above,  from 
the  last  of  May  till  the  first  of  August ;  frequently  examining  the 
edges  of  the  fluid  with  a  lens,  through  the  sides  of  the  glass  jar, 
but  without  ever  detecting  in  it  any  traces  of  living  organisms.  At 
the  end  of  that  period  the  flask  was  opened,  and  the  fluid  which  it 
contained  subjected  to  direct  examination,  equally  without  result. 
It  was  then  exposed,  in  the  same  vessel  and  in  the  same  situation 
as  before,  to  the  free  access  of  the  atmosphere,  and  at  the  end  of 
two  or  three  days  it  was  found  to  be  swarming  with  infusoria. 

It  is  plain,  therefore,  that  the  infusoria  cannot  be  regarded  as 
produced  by  spontaneous  generation,  but  must  be  considered  as 
originating  in  the  usual  manner  from  germs;  since  they  do  not 
make  their  appearance  in  the  watery  infusion,  when  the  accidental 
introduction  of  germs  from  without  has  been  effectually  prevented. 


Animal  and  Yegetable  Parasites. — This  very  remarkable 
group  of  organized  bodies  is  distinguished  by  the  fact  that  they 
live  either  upon  the  surface  or  in  the  interior  of  other  animal  or 
vegetable  organisms.     Thus,  the  mistletoe  fixes  itself  on  the  branches 


ANIMAL    AND    VEGETABLE    PARASITES.  538 

of  aged  trees ;  the  Oidium  albicans  vegetates  upon  the  mucous  sur- 
faces of  the  mouth  and  pharynx ;  the  Botrytis  Bassiana  attacks  the 
body  of  the  silkworm,  and  plants  itself  in  its  tissues ;  while  many 
species  of  tretnatoid  worms  live  attached  to  the  gills  of  fish  and  of 
water-lizards. 

These  parasites  are  usually  nourished  by  the  fluids  of  the  animal 
whose  body  they  inhabit.  Each  particular  species  of  parasite  is 
found  to  inhabit  the  body  of  a  particular  species  of  animal,  and  is 
not  found  elsewhere.  They  are  met  with,  moreover,  as  a  general 
rule,  only  in  particular  organs,  or  even  in  particular  parts  of  a 
single  organ.  Thus  the  Tricocephalus  dispar  is  found  only  in  the 
cascum ;  the  Strongylus  gigas  in  the  kidney ;  the  Distoma  hepati- 
cum  in  the  biliary  passages.  The  Distoma  variegatum  is  found 
only  in  the  lungs  of  the  green  frog,  the  Distoma  cylindraceum  in 
those  of  the  brown.  The  Tsenia  solium  is  found  in  the  intestine  of 
the  human  subject  in  certain  parts  of  Europe,  while  the  Tsenia  lata 
occurs  exclusively  in  others.  It  appears,  therefore,  as  though  some 
local  combination  of  conditions  were  necessary  to  the  production 
of  these  parasites;  and  they  have  been  supposed,  accordingly,  to 
originate  by  spontaneous  generation  in  the  localities  where  they 
are  exclusively  known  to  exist. 

A  little  consideration  will  show,  however,  that  the  above  condi- 
tions are  not,  properly  speaking,  necessary  or  sufficient  for  the 
production,  but  only  for  the  development  of  these  parasites.  All  the 
parasites  mentioned  above  reproduce  their  species  by  generation. 
They  have  male  and  female  organs,  and  produce  fertile  eggs,  often 
in  great  abundance.  The  eggs  contained  in  a  single  female  Ascaris 
are  to  be  counted  by  thousands ;  and  in  a  tapeworm,  it  is  said,  even 
by  millions.  Now  these  eggs,  in  order  that  they  may  be  hatched 
and  produce  new  individuals,  require  certain  special  conditions 
which  are  favorable  for  their  development ;  in  the  same  manner 
as  the  seeds  of  plants  require,  for  their  germination  and  growth,  a 
certain  kind  of  soil  and  a  certain  supply  of  warmth  and  moisture. 
It  is  accordingly  no  more  surprising  that  the  Ascaris  vermicularis 
should  inhabit  the  rectum,  and  the  Ascaris  lumbricoides  the  ileum, 
than  that  the  Lobelia  inflata  should  grow  only  in  dry  pastures,  and 
the  Lobelia  cardinalis  by  the  side  of  running  brooks.  The  lichens 
flourish  on  the  exposed  surfaces  of  rocks  and  stone  walls ;  while 
the  fungi  vegetate  in  darkness  and  moisture,  on  the  decaying  trunks 
of  dead  trees.  Yet  no  one  imagines  these  vegetables  to  be  spon- 
taneously generated  from  the  soil  which  they  inhabit.     The  truth 


534  NATURE    OF    REPRODUCTION. 

is  simply  this,  fhat  if  the  animal  or  vegetable  germ  be  deposited  in 
a  locality  which  affords  the  requisite  conditions  for  its  development, 
it  becomes  developed ;  otherwise  not.  Each  female  Ascaris  pro- 
duces, as  we  have  stated  above,  many  thousands  of  ova.  Now, 
though  the  chances  are  very  great  against  any  particular  one  of 
these  ova  being  accidentally  transported  into  the  intestinal  canal  of 
another  individual,  it  is  easy  to  see  that  there  are  many  causes  in 
operation  by  which  some  of  them  might  be  so  transported.  By  far 
the  greater  number  undoubtedly  perish,  from  not  meeting  with  the 
conditions  necessary  for  their  development.  One  in  a  thousand,  or 
perhaps  one  in  a  million,  is  accidentally  introduced  into  the  body 
of  another  individual,  and  consequently  becomes  developed  there 
into  a  perfect  Ascaris. 

The  circumstance,  therefore,  that  particular  parasites  are  confined 
to  particular  localities,  presents  no  greater  difficulty  as  to  their 
mode  of  reproduction,  than  the  same  fact  regarding  other  animal 
and  vegetable  organisms. 

Neither  is  there  any  difficulty  in  accounting  for  the  introduction 
of  parasitic  germs  into  the  interior  of  the  body.  The  air  and  the 
food  offer  a  ready  means  of  entrance  into  the  respiratory  and 
digestive  passages ;  and,  a  parasite  once  introduced  into  the  intes- 
tine, there  is  no  difficulty  in  accounting  for  its  presence  in  any  of 
the  ducts  leading  from  or  opening  into  the  alimentary  canal.  Some 
parasites  are  known  to  insinuate  themselves  directly  underneath 
the  surface  of  the  skin ;  as  the  Pulex  penetrans  or  "  chiggo"  of 
South  America,  and  the  Ixodes  Americanus  or  "tick,"  Others, 
like  the  (Estrus  bovis,  penetrate  the  integument  for  the  purpose  of 
depositing  their  eggs  in  the  subcutaneous  areolar  tissue.  Some 
may  even  gain  an  entrance  into  the  bloodvessels,  and  circulate  in 
this  way  all  over  the  body.  Thus  the  Filaria  rubella  is  found  alive 
in  the  bloodvessels  of  the  frog,  the  Distoma  haematobium  in  those 
of  the  human  subject,  and  a  species  of  Spiroptera  in  those  of  the 
dog.  It  is  easy  to  see,  therefore,  how,  by  such  means,  parasitic 
germs  may  be  conveyed  to  any  part  of  the  body ;  and  may  even  be 
deposited,  by  accidental  arrest  of  the  circulation,  in  the  substance 
of  the  solid  organs. 

The  most  serious  difficulty,  however,  in  the  way  of  accounting 
for  the  production  of  parasitic  organisms,  was  that  presented  by  the 
existence  of  a  class  known  as  the  encysted  or  sexless  entozoa.  These 
parasites  for  the  most  part  occupy  the  interior  of  the  solid  organs 
and  tissues,  into  which  they  could  not  have  gained  access  by  the 


ANIMAL    ANJD    VEGETABLE    PARASITES.  535 

mucous  canals.  Thus  the  CcBnurus  cerebralis  is  found  imbedded 
in  the  substance  of  the  brain,  the  Trichina  spiralis  between  the 
fibres  of  the  voluntary  muscles,  and  the  Cysticercus  cellulosae  in  the 
areolar  tissue  of  various  parts  of  the  body.  They  are  also  distin- 
guished from  all  other  parasites  by  two  peculiar  characters.  First, 
they  are  inclosed  in  a  distinct  cyst,  with  which  they  have  no  organic 
connection  and  from  which  they  may  be  readily  separated ;  and  se- 
condly, they  have  no  genera- 
tive organs,  nor  is  there  any     ^'g-  170. 

difference  between  ^^^^^^^^^^^^^^^^^^^| 
the  sexes.  The  Trichina  spi-  ^^^^^^PUf^p^P^^I^^^^^^B 
ralis,  for  example  (Fig.  170),  ^^^^^KiWyf (^T^SSII^^^M 
is  inclosed  in  an  ovoid  or  ^^MiE||||tAAA 
spindle-shaped  cyst,  swollen  ^^^^|HM^^||^|||^^^^m^9 
in  the  middle  and  tapering  at  H^^^^^^^^^H^^H||Hi||ifl 
each  extremity,  with  a  round-       ^  ^  ,         .    ,      . 

'^  '  Tbich  IN  A  SPIB  A  1. 1  8  ;  from  rectus  femon.s  mua- 

ed    cavity  in    its    central    por-       cle  of  human  subject.     Magnified  57  diameters. 

tion,  in  which  the  worm  lies 

coiled  up  in  a  spiral  form.     The  worm  itself  has  neither  testicles 

nor  ovaries,  nor  does  it  present  any  trace  of  a  sexual  organization. 

Now  we  have  seen  that  it  is  easy  to  account  for  the  conveyance 
of  these  or  any  other  parasites  into  the  interior  of  vascular  organs 
and  tissues ;  the  eggs  from  which  they  are  produced  being  trans- 
ported by  the  bloodvessels  to  any  part  of  the  body,  and  there 
retained  by  a  local  arrest  of  the  capillary  circulation.  In  the  case 
of  the  encysted  entozoa,  however,  we  have  a  much  greater  diffi- 
culty ;  since  these  parasites  are  entirely  without  sexual  organs  or 
generative  apparatus  of  any  sort,  nor  have  they  ever  been  dis- 
covered in  the  act  of  producing  eggs,  or  of  developing  in  any 
manner  a  progeny  similar  to  themselves.  It  appears,  accordingly, 
difficult  to  understand  how  animals,  which  are  without  a  sexual 
apparatus,  should  have  been  produced  by  sexual  generation.  As 
it  is  certain  that  they  can  have  no  progeny,  it  would  seem  equally 
evident  that  they  must  have  been  produced  without  a  parentage. 

This  difficulty,  however,  serious  as  it  at  first  appears,  is  susceptible 
of  a  very  simple  explanation.  The  case  is  in  many  respects  analogous 
to  that  of  the  maggots,  hatched  from  the  eggs  of  flies  in  putrefying 
meat.  These  maggots  are  also  without  sexual  organs;  for  they 
are  still  imperfectly  developed,  and  in  a  kind  of  embryonic  condi- 
tion. It  is  only  after  their  metamorphosis  into  perfect  insects,  that 
generative  organs  are  developed    and  a  distinction   between   the 


536 


NATURE    OF    REPRODUCTION, 


sexes  manifests  itself.  This  is,  indeed,  more  or  less  the  case  witli 
all  animals  and  with  all  vegetables.  The  blossom,  which  is  the 
sexual  apparatus  of  the  plant,  does  not  appear,  as  a  general  rule, 
until  the  growth  of  the  vegetable  has  continued  for  a  certain  time, 
and  it  has  acquired  a  certain  age  and  strength.  Even  in  the  human 
subject  the  sexual  organs,  though  present  at  birth,  are  still  very 
imperfectly  developed  as  to  size,  and  altogether  inactive  in  func- 
tion. It  is  only  later  that  these  organs  acquire  their  full  growth, 
and  the  sexual  characters  become  complete.  In  very  many  of  the 
lower  animals  the  sexual  organs  are  entirely 
Fig.  171.  absent  at  birth,  and  appear  only  at  a  later 

period  of  development. 

Now  the  encysted  or  sexless  entozoa  are 
simply  the  undeveloped  young  of  other  para- 
sites which  propagate  by  sexual  generation ; 
the  membrane  in  which  they  are  inclosed 
being  either  an  embryonic  envelope,  or  else 
an  adventitious  cyst  formed  round  the  para- 
sitic embryo.  These  embryos  have  come,  in 
the  natural  course  of  their  migrations,  into 
a  situation  which  is  not  suitable  for  their  com- 
plete development.  Their  development  is 
accordingly  arrested  before  it  arrives  at  matu- 
rity ;  and  the  parasite  never  reaches  the  adult 
condition," until  removed  from  the  situation  in 
which  it  has  been  placed,  and  transported  to  a 
more  favorable  locality. 

The  above  explanation  has  been  demon- 
strated to  be  the  true  one,  more  particularly 
with  regard  to  the  Taenia,  or  tapeworm,  and 
several  varieties  of  Cysticercus.  The  Tsenia 
(Fig.  171)  is  a  parasite  of  which  different  species 
are  found  in  the  intestine  of  the  human  subject, 
the  dog,  cat,  fox,  and  other  of  the  lower  animals. 
T^NiA.  Its  upper  extremity,  termed  the  "head,"  con- 

sists of  a  nearly  globular  mass,  presenting  upon 
its  lateral  surfaces  a  set  of  four  muscular  disks,  or  "  suckers,"  and 
terminating  anteriorly  in  a  conical  projection  which  is  provided 
with  a  crown  of  curved  processes  or  hooks,  by  which  the  parasite 
attaches  itself  to  the  intestinal  mucous  membrane.  To  this  "head" 
succeeds  a  slender  ribbon-shaped  neck,  which  is  at  first  smooth,  but 


ANIMAL    AND    VEGETABLE    PARASITES. 


537 


which  soon  becomes  transversely  wrinkled,  and  afterward  divided 
into  distinct  rectangular  pieces  or  "articulations."     These  articula- 
tions multiply  by  a  process  of  successive  growth  or  budding,  from 
the  wrinkled  portion  of  the  neck ;  and  are  constantly  removed  farther 
and  farther  from  their  point  of  origin  by  new  ones  formed  behind 
them.     As   they  gradually  descend,  by   the   process   of  growth, 
farther  down  the  body  of  the  tapeworm,  they  become  larger  and 
begin  to  exhibit  a  sexual  apparatus,  developed  in  their  interior. 
In  each  fully  formed  articulation  there  are  contained  both  male 
and  female  organs  of  generation ;  and  the  mature  eggs,  which  are 
produced  in  great  numbers,  are  thrown  off  together  with  the  articu- 
lation itself  from  the  lower  extremity  of  the  tapeworm.     Since  the 
articulations  are  successively  produced,  as  we  have  mentioned  above, 
by  budding  from  the  neck  and  the  back  part  of  the  head,  the  para- 
site cannot  be  effectually  dislodged  by  taking  away  any  portion  of 
the  body,  however  large ;  since  it  is  subsequently  reproduced  from 
the  head,  and  continues  its  growth  as  before.     But  if  the  head  itself 
be  removed  from  the  intestine,  no  further  reproduction  of  the  articu- 
lations can  take  place. 

The  Cysticercus  is  an  encysted  parasite,  different  varieties  of  which 
are  found  in  the  liver,  the  peritoneum,  and  the  meshes  of  the  areolar 
tissue  in  various  parts  of  the  body.  It  consists  (Fig.  172)  first,  of 
a  globular  sac,  or  cyst  (a),  which  is  not  adherent  to  the  tissues  of 
the  organ  in  which  the  parasite  is  found,  but  may  be  easily  sepa- 


Fig.  172. 


Fig.  173. 


CTSTicERCug.— a.  External  cyst,  h  In- 
ternal sac,  containing  fluid,  c.  Narrow  canal, 
formed  by  involntion  of  walls  of  sac,  at  the 
bottom  of  which  is  the  head  of  the  tsenia. 


Cysticercus,  unfolded. 


rated  from  them.  In  its  interior  is  found  another  sac  {h),  lying 
loose  in  the  cavity  of  the  former,  and  filled  with  a  serous  fluid. 
This  second  sac  presents,  at  one  point  upon  its  surface,  a  puckered 
depression,  leading  into  a  long,  narrow  canal  (c).     This  canal,  which 


538  NATURE    OF    REPRODUCTION. 

is  formed  hy  an  involution  of  the  walls  of  the  second  sac,  presents 
at  its  bottom  a  small  globular  mass,  like  the  head  of  the  Taenia, 
provided  with  suckers  and  hooks,  and  supported  upon  a  short 
slender  neck.  If  the  outer  investing  sac  be  removed,  the  narrow 
canal  just  described  may  be  everted  by  careful  manipulation,  and 
the  parasite  will  then  appear  as  in  Fig.  173,  with  the  head  and  neck 
resembling  those  of  a  Taenia,  but  terminating  behind  in  a  dropsical 
sac-like  swelling,  instead  of  the  chain  of  articulations  which  are 
characteristic  of  the  fully  formed  tapeworm. 

Now  it  has  been  shown,  by  the  experiments  of  Kiichenmeister, 
Siebold,  and  others,  that  the  Cysticercus  is  only  the  imperfectly 
developed  embryo,  or  young,  of  the  Taenia.  When  the  mature 
articulation  of  the  tapeworm  is  thrown  oft]  as  already  mentioned, 
from  its  posterior  extremity,  the  eggs  which  it  incloses  have  already 
passed  through  a  certain  period  of  development,  so  that  each  one 
contains  an  imperfectly  formed  embryo.  The  articulation,  contain- 
ing the  eggs  and  embryos,  is  then  taken,  with  the  food,  into  the 
stomach  of  another  animal;  the  substance  of  the  articulation,  to- 
gether with  the  external  covering  of  the  eggs,  is  destroyed  by  di- 
gestion, and  the  embryos  are  thus  set  free.  They  then  penetrate 
through  the  walls  of  the  stomach,  into  the  neighboring  organs  or 
the  areolar  tissue,  and  becoming  encysted  in  these  situations,  are 
there  developed  into  cysticerci,  as  represented  in  Fig.  172.  After- 
ward, the  tissues  in  which  they  are  contained  being  devoured  by 
a  third  animal,  the  cysticercus  passes  into  the  intestine,  fixes  itself 
to  the  mucous  membrane,  and,  by  a  process  of  budding,  produces 
the  long  tape-like  series  of  articulations,  by  which  it  is  finally  con- 
verted into  the  full-grown  Taenia. 

Prof  Siebold  found  the  head  of  the  Cysticercus  fasciolaris,  met 
with  in  the  liver  of  rats  and  mice,  presenting  so  close  a  resem- 
blance to  the  Taenia  crassicollis,  inhabiting  the  intestine  of  the  cat, 
that  he  was  led  to  believe  the  two  parasites  to  be  identical.  This 
identity  was,  in  fact,  proved  by  the  experiments  of  Kiichenmeister ; 
and  Siebold  afterward  demonstrated'  the  same  relation  to  exist 
between  the  Cysticercus  pisiformis,  found  in  the  peritoneum  of  rab- 
bits, and  the  Taenia  serrata,  from  the  intestine  of  the  dog.  This 
experimenter  succeeded  in  administering  to  dogs  a  quantity  of  the 
cysticerci,  fresh  from  the  body  of  the  rabbit,  mixed  with  milk ;  and 

'  In  Buffalo  Medical  Journal,  Feb.  1853  ;  also  in  Siebold  on  Tape  and  Cystic 
vVornis,  Sydenham  translation:  London,  1857,  p.  59. 


ANIMAL    AXD    VEGETABLE    PAEASITES.  539 

on  killing  the  dogs,  at  various  periods  after  the  meal,  from  three 
hours  to  eight  weeks,  he  found  the  cysticerci  in  various  stages  of 
development  in  the  intestine,  and  finally  converted  into  the  full 
grown  Tgenia,  with  complete  articulations  and  mature  eggs. 

Dr.  Kiichenmeister'  has  also  performed  the  same  experiment,  with 
success,  on  the  human  subject.  A  number  of  cysticerci  were  ad- 
ministered to  a  criminal,  at  different  periods  before  his  execution, 
varying  from  12  to  72  hours ;  and  upon  post-mortem  examination 
of  the  body,  no  less  than  ten  young  taeniee  were  found  in  the 
intestine,  four  of  which  could  be  distinctly  recognized  as  specimens 
of  Taenia  solium. 

Finally,  both  Leuckart  and  Kiichenmeister^  have  shown,  on  the 
other  hand,  that  the  eggs  of  Taenia  solium,  introduced  into  the  body 
of  the  pig,  will  give  rise  to  the  development  of  Cysticercus  cellulosae ; 
thus  demonstrating  that  the  two  kinds  of  parasites  are  identical  in 
their  nature,  and  differ  only  in  the  manner  and  degree  of  their 
development. 

There  remains,  accordingly,  no  good  reason  for  believing  that 
even  the  encysted  parasites  are  produced  by  spontaneous  genera- 
tion. Whatever  obscurity  may  hang  round  the  origin  or  reproduc- 
tion of  any  class  or  species  of  animals,  the  direct  investigations  of 
the  physiologist  always  tend  to  show  that  they  do  not,  in  reality, 
form  any  exception  to  the  general  law  in  this  respect ;  and  the  only 
opinion  which  is  admissible,  from  the  facts  at  present  within  our 
knowledge,  is  that  organizedheings,  animal  and  vegetable,  wherever  they 
may  he  found,  are  always  the  -progeny  of  previously  existing  parents. 

'  On  Animal  and  Vegetable  Parasites,  Sydenham  translation :  London,  1857, 
p.  115. 

*  Op.  cit.,  p.  120. 


540 


SEXUAL    GENERATION. 


CHAPTEB,   II. 

ON  SEXUAL  GENEEATION,  AND  THE  MODE  OF  ITS 
ACCOMPLISHMENT. 


Fig.  174. 


The  function  of  generation  is  performed  by  means  of  two  sets  of 
organs,  each  of  which  gives  origin  to  a  peculiar  product,  capable 
of  uniting  with  the  other  so  as  to  produce  a  new  individual.    These 

two  sets  of  organs,  belonging  to  the 
two  different  sexes,  are  called  the  male 
and  female  organs  of  generation.  The 
female  organs  produce  a  globular  body 
called  the  germ,  or  egg,  which  is  capable 
of  being  developed  into  the  body  of 
the  young  animal  or  plant ;  the  male 
organs  produce  a  substance  which  is 
necessary  to  fecundate  the  germ,  and 
enable  it  to  go  through  with  its  natural 
growth  and  development. 

Such  are  the  only  essential  and  uni- 
versal characters  of  the  organs  of  gene- 
ration. These  organs,  however,  exhibit 
various  additions  and  modifications  in 
different  classes  of  organized  beings, 
while  they  show  throughout  the  same 
fundamental  and  essential  characters. 
In  the  flowering  plants,  for  example, 
the  blossom,  which  is  the  generative 
apparatus  (Fig.  174),  consists  first  of  a 
female  organ  containing  the  germ  (a),  situated  usually  upon  the 
highest  part  of  the  leaf-bearing  stalk.  This  is  surmounted  by  a 
nearly  straight  column,  termed  the  pistil  (5),  dilated  at  its  summit 
into  a  globular  expansion,  and  occupying  the  centre  of  the  flower. 
Around  it  are  arranged  several  slender  filaments,  or  stamens,  bear- 
ing upon  their  extremities  the  male  organs,  or  anthers  (c,  c).     The 


Blossom  of  CoNvoLVtritrs 
PuRPURECS.  (Morning  glory.) — a. 
Germ.  6.  Pistil,  c.  c.  Stamens,  with 
anthers,    d.  Corolla,    e.  Calyx. 


SEXUAL    GENEP.ATIOISr. 


541 


Fig.  175. 


■wliole  is  surrounded  by  a  circle  or  crown  of  delicate  and  brilliantly 
colored  leaves,  termed  tbe  corolla  (d),  which  is  frequently  provided 
with  a  smaller  sheath  of  green  leaves  outside,  called  the  calyx  (e). 
The  anthers,  when  arrived  at  maturity,  discharge  a  fine  organic 
dust,  called  the  pollen,  the  granules  of  which  are  caught  upon  the 
extremity  of  the  pistil,  and  then  penetrate  downward  through  its 
tissues,  until  they  reach  its  lower  extremity  and  come  in  contact 
with  the  germ.  The  germ  thus  fecundated,  the  process  of  genera- 
tion is  accomplished.  The  pistil,  anthers,  and  corolla  wither  and 
fall  ofij  while  the  germ  increases  rapidly  in  size,  and  changes  in 
form  and  texture,  until  it  ripens  into  the  mature  fruit  or  seed.  It 
is  then  ready  to  be  separated  from  the  parent  stem ;  and,  if  placed 
in  the  proper  soil,  will  germinate  and  at  last  produce  a  new  plant 
similar  to  the  old. 

In  the  above  instance,  the  male  and  female  organs  are  both 
situated  upon  the  same  flower ;  as  in  the  lily,  the  violet,  the  con- 
volvulus, &c.  In  other  cases,  there  are  separate  male  and  female 
flowers  upon  the  same  plant,  of  which  the  male  flowers  produce 
only  the  pollen,  the  female,  the 
germ  and  fruit.  In  others  still, 
the  male  and  female  flowers  are 
situated  upon  different  plants, 
which  otherwise  resemble  each 
other,  as  in  the  willow,  poplar, 
and  hemp. 

In  animals,  the  female  organs 
of  generation  are  called  ovaries, 
since  it  is  in  them  that  the  egg, 
or  "ovum,"  is  produced.  The 
male  organs  are  the  testicles, 
which  give  origin  to  the  fecun- 
dating product,  or  "seminal 
fluid,"  by  which  the  egg  is  fer- 
tilized. We  have  already  men- 
tioned above  that  in  the  articula- 
tions of  the  tapeworm  the  ovaries 
and  testicles  are  developed  to- 
gether. (Fig.  175.)  The  ovary 
(a,  a,  a)  is  a  series  of  branching  follicles  terminating  in  rounded 
extremities,  and  communicating  with  each  other  by  a  central  canal. 
The  testicle  {b)  is  a  narrow,  convoluted  tube,  very  much  folded 


SrNQLE  Articulation  of  Taenia 
Ckassicolms,  from  small  intestine  of  cat. — 
a,  a,  a.  Ovary  filled  with  eggs.  b.  Testicle,  c. 
Genital  orifice. 


542  SEXUAL    GENERATION. 

■upon  itself,  whicli  opens  by  an  external  orifice  (c)  upon  the  lateral 
border  of  the  articulation,  about  midway  between  its  two  ex- 
tremities. The  spermatic  fluid  produced  in  the  testicle  is  intro- 
duced into  the  female  generative  passage,  which  opens  at  the  same 
spot,  and,  penetrating  deeply  into  the  interior,  comes  in  contact 
with  the  eggs,  which  are  thereby  fecundated  and  rendered  fertile. 
The  fertile  eggs  are  afterward  set  free  by  the  rupture  or  decay  of 
the  articulation,  and  a  vast  number  of  young  are  produced  by  their 
development. 

In  snails,  also,  and  in  som«  other  of  the  lower  animals,  the  ovaries 
and  testicles  are  both  present  in  the  same  individual ;  so  that  these 
animals  are  sometimes  said  to  be  "  hermaphrodite,"  or  of  double 
sex.  In  reality,  however,  it  appears  that  the  male  and  female 
organs  do  not  come  to  maturity  at  the  same  time ;  but  the  ovaries 
are  first  developed  and  perform  their  function,  after  which  the  tes- 
ticles come  into  activity  in  their  turn.  The  same  individual,  there- 
fore, is  not  both  male  and  female  at  any  one  time;  but  is  first 
female  and  afterward  male,  exercising  the  two  generative  functions 
at  different  ages. 

In  all  the  higher  animals,  however,  the  two  sets  of  generative 
organs  are  located  in  separate  individuals;  and  the  species  is 
consequently  divided  into  two  sexes,  male  and  female.  All  that 
is  absolutely  requisite  to  constitute  the  two  sexes  is  the  existence 
of  testicles  in  the  one,  and  of  ovaries  in  the  other.  Beside  these, 
however,  there  are,  in  most  instances,  certain  secondary  or  acces- 
sory organs  of  generation,  which  assist  more  or  less  in  the  accom- 
plishment of  the  process,  and  which  occasion  a  greater  difference  in 
the  anatomy  of  the  two  sexes.  Such  are  the  uterus  and  mammary 
glands  of  the  female,  the  vesiculae  seminales  and  prostate  gland 
of  the  male.  The  female  naturally  having  the  immediate  care  of 
the  young  after  birth,  and  the  male  being  occupied  in  providing 
food  and  protection  for  both,  there  are  also  corresponding  differ- 
ences in  the  general  structure  of  the  body,  which  affect  the  whole 
external  appearance  of  the  two  sexes,  and  which  even  show  them- 
selves in  their  mental  and  moral,  as  well  as  in  their  physical 
characteristics.  In  some  cases  this  difference  is  so  excessive  that 
the  male  and  female  would  never  be  recognized  as  belonging  to  the 
same  species,  unless  they  were  seen  in  company  with  each  other. 
Not  to  mention  some  extreme  instances  of  this  among  insects  and 
other  invertebrate  animals,  it  will  be  sufficient  to  refer  to  the  well- 
known  examples  of  the  cock  and  the  hen,  the  lion  and  lioness,  the 


SEXUAL    GENERATION.  543 

buck  and  the  doe.  In  the  human  species,  also,  the  distinction 
between  the  sexes  shows  itself  in  the  mental  constitution,  the  dis- 
position, habits,  and  pursuits,  as  well  as  in  the  general  conforma- 
tion of  the  body,  and  the  peculiarities  of  external  appearance. 

We  shall  now  study  more  fully  the  character  of  the  male  and 
female  organs  of  generation,  together  with  their  products,  and  the 
manner  in  which  these  ai'e  discharged  from  the  body,  and  brought 
into  relation  with  each  other. 


544 


EGG  AND  FEMALE  ORGANS  OF  GENERATION. 


CHAPTEE  III. 

ON  THE  EGG,  AND  THE  FEMALE  ORGANS  OF 
GENERATION. 


Fig.  176. 


The  egg  is  a  globular  body  which  varies  considerably  in  size  in 
different  classes  of  animals,  according  to. the  peculiar  conditions 
under  which  its  development  is  to  take  place.  In  the  frog  it  mea- 
sures x'5  of  an  inch  in  diameter,  in  the  lamprey  3^,  in  quadrupeds 
and  in  the  human  species  yi^.  It  consists,  first,  of  a  membranous 
external  sac  or  envelope,  the  vitelline  membrane;  and  secondly,  of  a 
spherical  mass  inclosed  in  its  interior,  called  the  vitellus. 

The  vitelline  membrane  in  birds  and  reptiles  is  very  thin,  measur- 
ing often  not  more  than  y^^^^  of  an  inch  in  thickness,  and  is  at  the 

same  time  of  a  somewhat  fibrous  texture. 
In  man  and  the  higher  animals,  on  the 
contrary,  it  is  perfectly  smooth,  structure- 
less and  transparent,  and  is  about  y  5V7  of 
an  inch  in  thickness.  Notwithstanding 
its  delicate  and  transparent  appearance,  it 
has  a  considerable  degree  of  resistance 
and  elasticity.  The  egg  of  the  human 
subject,  for  example,  may  be  perceptibly 
flattened  out  under  the  microscope  by 
pressing  with  the  point  of  a  needle  upon 
the  slip  of  glass  which  covers  it;  but  it 
still  remains  unbroken,  and  when  the 
pressure  is  removed,  readily  resumes  its  globular  form.  When  the 
egg  is  somewhat  flattened  under  the  microscope  in  this  way,  by 
pressure  of  the  glass  slip,  the  apparent  thickness  of  the  vitelline 
membrane  is  increased,  and  it  then  appears  (Fig.  176)  as  a  rather 
wide,  colorless,  and  pellucid  border  or  zone,  surrounding  the  granu- 
lar and  opaque  vitellus.  Owing  to  this  appearance,  it  has  some- 
times received  the  name  of  the  "  zona  pellucida."     The  name  of 


HcMAN  Ovum,  magnified  S5 
diameters,  a.  Vitelline  membrane. 
6.  Vitellus.  c.  Germinative  vesicle. 
d.  Germinative  spot. 


EGG  AXD  FEMALE  ORGANS  OF  GENERATION.    545 

vitelline  membrane,  however,  is  the  one  more  generally  adopted, 
and  is  also  the  more  appropriate  of  the  two. 

The  vitellus  (h)  is  a  globular,  semi-solid  mass,  contained  within 
the  vitelline  membrane.  It  consists  of  a  colorless  albuminoid  sub- 
stance, with  an  abundance  of  minute  molecules  and  oleaginous 
granules  scattered  through  it.  These  minute  oleaginous  masses 
give  to  the  vitellus  a  partially  opaque  and  granular  aspect  under 
the  microscope.  Imbedded  in  the  vitellus,  usually  near  its  surface 
and  almost  immediately  beneath  the  vitelline  membrane,  there  is  a 
clear,  colorless,  transparent  vesicle  (c)  of  a  rounded  form,  known 
as  the  germinative  vesicle.  In  the  egg  of  the  human  subject  and  of 
the  quadrupeds,  this  vesicle  measures  ^\-q  to  -^{^  of  an  inch  in 
diameter.  It  presents  upon  its  surface  a 
dark  spot,  like  a  nucleus  (cZ),  which  is  known  =" 

by  the  name  of  the  germinative  spot.  The 
germinative  vesicle,  with  its  nucleus-like 
spot,  is  often  partially  concealed  by  the 
granules  of  the  vitellus  by  which  it  is  sur- 
rounded, but  it  may  always  be  discovered 
by  careful  examination. 

If  the  Qgg  be  ruptured  by  excessive  pres-  human  ovfm,  ruptured  by 
sure  under  the  microscope,  the  vitellus  is    p'«'*^"«:  showing  the  viteiius 

^  ^  partially  expelled,  the  germina- 

seen  to  have  a  gelatinous  consistency.  It  tive  vesicle  at  a,  and  the  smooth 
is  gradually  expelled  from  the  vitelline  ;';;;^;'  °'  "^'  ""'"'"'  '"''"■ 
cavity,  but  still  retains  the  granules  and  oil 

globules  entangled  in  its  substance.  (Fig.  177.)  The  edges  of  the 
fractured  vitelline  membrane,  under  these  circumstances,  present  a 
smooth  and  nearly  straight  outline,  without  any  appearance  of 
laceration  or  of  a  fibrous  structure.  The  membrane  is,  to  all  ap- 
pearance, perfectly  homogeneous. 

The  most  essential  constituent  of  the  egg  is  the  vitellus.  It  is 
from  the  vitellus  that  the  body  of  the  embryo  will  afterward  be 
formed,  and  the  organs  of  the  new  individual  developed.  The 
vitelline  membrane  is  merely  a  protective  inclosure,  intended  to 
secure  the  vitellus  from  injury,  and  enable  it  to  retain  its  figure 
during  the  early  periods  of  development. 

The  Qgg,  as  above  described,  consists  therefore  of  a  simple 
vitellus  of  minute-  size,  and  a  vitelline  membrane  inclosing  it.  It 
is  such  an  egg  which  is  found  in  the  human  subject,  the  quadru- 
peds, most  aquatic  reptiles,  very  many  fish,  and  some  invertebrate 
animals.  In  nearly  all  those  species,  in  fact,  where  the  fecundated 
'6b 


546     EGG  AND  FEMALE  ORGA^'S  OF  GENERATION. 

eggs  are  deposited  and  hatched  in  the  water,  as  well  as  those  in 
which  they  are  retained  in  the  body  of  the  female  until  the  develop- 
ment of  the  young  is  completed,  such  an  egg  as  above  described  is 
sufficient  for  the  formation  of  the  embryo ;  since  during  its  develop- 
ment it  can  absorb  freely,  either  from  the  water  in  which  it  floats, 
or  from  the  mucous  membrane  of  the  female  generative  organs,  the 
requisite  supply  of  nutritious  fluids.  But  in  birds  and  in  the 
terrestrial  reptiles,  such  as  lizards,  tortoises,  &c.,  where  the  eggs 
are  expelled  from  the  body  of  the  female  at  an  early  period,  and 
incubated  on  land,  there  is  no  external  source  of  nutrition,  to  pro- 
vide for  the  support  of  the  young  animal  during  its  development. 
In  these  instances  accordingly  the  vitellus,  or  "yolk,"  as  it  is  called, 
is  of  very  large  size ;  and  the  bulk  of  the  egg  is  still  further  in- 
creased by  the  addition,  within  the  female  generative  passages,  of 
layers  of  albumen  and  various  external  fibrous  and  calcareous 
envelopes.  The  essential  constituents  of  the  egg,  however,  still 
remain  the  same  in  character,  and  the  process  of  embryonic  deve- 
lopment follows  the  same  general  laws  as  in  other  cases. 

The  eggs  are  produced  in  the  interior  of  certain  organs,  situated 
in  the  abdominal  cavity,  called  the  ovaries.  These  organs  consist 
of  a  number  of  globular  sacs,  or  follicles,  known  as  the  "  Graafian 
follicles,"  each  one  of  which  contains  a  single  egg.  The  follicles 
are  connected  with  each  other  by  a  quantity  of  vascular  areolar 
tissue,  which  binds  them  together  into  a  well-defined  and  consistent 
mass,  covered  upon  its  exterior  by  a  layer  of  peritoneum.  The 
egg  has  sometimes  been  spoken  of  as  a  "product,"  or  even  as  a 
"  secretion"  of  the  ovary.  Nothing  can  be  more  inappropriate, 
however,  than  to  compare  the  egg  with  a  secretion,  or  to  regard  the 
ovary  as  in  any  respect  resembling  a  glandular  organ.  The  egg  is 
simply  an  organized  body,  growing  in  the  ovary  like  a  tooth  in  its 
follicle,  and  forming  a  constituent  part  of  the  body  of  the  female. 
It  is  destined  to  be  finally  separated  from  its  attachments  and 
thrown  off;  but  until  that  time,  it  is,  properly  speaking,  a  part  of 
the  ovarian  texture,  and  is  nourished  like  any  other  portion  of  the 
female  organism. 

The  ovaries,  accordingly,  since  they  are  directly  concerned  in 
the  production  of  the  eggs,  are  to  be  regarded  as  the  essential 
parts  of  the  female  generative  apparatus.  Beside  them,  however, 
there  are  usually  present  certain  other  organs,  which  play  a  secon- 
dary or  accessory  part  in  the  process  of  generation.  The  most 
important  of  these  accessory  organs  are  two  symmetrical  tubes,  or 


EGG  AND  FEMALE  ORGANS  OF  GENERATION. 


547 


Fig.  178. 


oviducts,  which  are  destined  to  receive  the  eggs  at  their  internal 
extremity  and  convey  them  to  the  external  generative  orifice.  The 
mucous  membrane  lining  the  oviducts  is  also  intended  to  supply 
certain  secretions  during  the  passage  of  the  egg,  which  are  requi- 
site either  to  complete  its  structure,  or  to  provide  for  the  nutrition 
of  the  embryo. 

In  the  frog,  for  example,  the  oviduct  commences  at  the  upper 
part  of  the  abdomen,  by  a  rather  wide  orifice,  which  communicates 
directly  with  the  peritoneal  cavity.  It 
soon  after  contracts  to  a  narrow  tube, 
and  pursues  a  zigzag  course  down  the 
side  of  the  abdomen  (Fig.  178),  folded 
upon  itself  in  convolutions,  like  the 
small  intestine,  until  it  opens,  near  its 
fellow  of  the  opposite  side,  into  the 
"■  cloaca"  or  lower  part  of  the  intestinal 
canal.  The  oviducts  present  the  same 
general  characters  with  those  described 
above,  in  nearly  all  species  of  reptiles 
and  birds ;  though  there  are  some  modi- 
fications, in  particular  instances,  which 
do  not  require  any  special  notice. 

The  ovaries,  as  well  as  the  eggs  which 
they  contain,  undergo  at  particular  sea- 
sons a  periodical  development  or  increase 
in  growth.  If  we  examine  the  female 
frog  in  the  latter  part  of  summer  or  the 
fell,  we  shall  find  the  ovaries  presenting 

the  appearance  of  small  clusters  of  minute  and  nearly  colorless 
eggs,  the  smaller  of  which  are  perfectly  transparent  and  not  over 
■x\-^  of  an  inch  in  diameter.  But  in  the  early  spring,  when  the 
season  of  reproduction  approaches,  the  ovaries  will  be  found  in- 
creased to  four  or  five  times  their  former  size,  ;and  forming  large 
lobulated  masses,  crowded  with  dark-colored  opaque  eggs,  measur- 
ing j'j  of  an  inch  in  diameter.  At  the  approach  of  the  generative 
season,  in  all  the  lower  animals,  a  certain  number  of  the  eggs,  which 
were  previously  in  an  imperfect  and  inactive  condition,  begin  to 
increase  in  size  and  become  somewhat  altered  in  structure.  The 
vitellus  more  especially,  which  was  before  colorless  and  transparent, 
becomes  granular  in  texture  as  well  as  increased  in  volume;  and 
assumes  at  the  same  time,  in  many  species  of  animals,  a  black, 


Female  Generativf,  Or- 
gans OF  Fkog. — «,  ".  Ovaries. 
6,  6.  Oviducts,  c,  c.  Their  iaternal 
orifices,  d.  Cloaca,  showing  exter- 
nal orifices  of  oviducts. 


548     EGG  AM)  FEMALE  ORGANS  OF  GENERATION". 

brown,  yellow,  or  orange  color.  In  the  human  subject,  however, 
the  change  consists  only  in  an  increase  of  size  and  granulation, 
without  any  remarkable  alteration  of  color. 

The  eggs,  as  they  ripen  in  this  way,  becoming  enlarged  and 
changed  in  texture,  gradually  distend  the  Graafian  follicles  and 
project  from  the  surface  of  the  ovary.  At  last,  when  fully  ripe, 
they  are  discharged  by  a  rupture  of  the  walls  of  the  follicles,  and, 
passing  into  the  oviducts,  are  conveyed  by  them  to  the  external 
generative  orifice,  and  there  expelled.  In  this  way,  as  successive 
seasons  come  round,  successive  crops  of  eggs  enlarge,  ripen,  leave 
the  ovaries,  and  are  discharged.  Those  which  are  to  be  expelled 
at  the  next  generative  epoch  may  always  be  recognized  by  their 
greater  degree  of  development ;  and  in  this  way,  in  many  animals, 
the  eggs  pf  no  less  than  three  different  crops  may  be  recongized  in 
the  ovary  at  once,  viz.,  1st,  those  which  are  perfectly  mature  and 
ready  to  be  discharged ;  2d,  those  which  are  to  ripen  in  the  follow- 
ing season ;  and  3d,  those  which  are  as  yet  altogether  inactive  and 
undeveloped.  In  most  fish  and  reptiles,  as  well  as  in  birds,  this 
regular  process  of  maturation  and  discharge  of  eggs  takes  place 
but  once  a  year.  In  different  species  of  quadrupeds  it  may  take 
place  annually,  semi-annually,  bi-monthly,  or  even  monthly;  but 
in  every  instance  it  recurs  at  regular  intervals,  and  exhibits  accord- 
ingly, in  a  marked  degree,  the  periodic  character  which  we  have 
seen  to  belong  to  most  of  the  other  vital  phenomena. 

Action  of  the  Oviducts  and  Female  Generative  Passages. — In  frogs 
and  lizards,  the  ripening  and  discharge  of  the  eggs  take  place,  as 
above  mentioned  in  the  early  spring.     At  the  time  of  leaving  the 

ovary,  the  eggs  consist  simply  of  the 
'=■    '"  dark-colored   and   granular  vitellus, 

inclosed  in  the  vitelline  membrane. 
They  are  then  received  by  the  inner 
o'®®a  ^^^^^"^      extremity  of  the  oviducts,  and  carried 

'^  downward  by  the  peristaltic  move- 

ment of  these  canals,  aided  by  the 
matfre  Frogs' Eggs.— fl.  While     morc   powcrful    Contraction    of    the 
r4°.  l'o;Z..  '•  ""  ""'"^     abdominal  muscles.    During  the  pas- 

sage  of  the  eggs,  moreover,  the  mucous 
membrane  of  the  oviduct  secretes  a  colorless,  viscid,  albuminoid 
substance,  which  is  deposited  in  successive  layers  round  each  egg, 
forming  a  thick  and  tenacious  coating  or  envelope,  (Fig.  179.) 
When  the  eggs  are  finally  discharged,  this   albuminoid   matter 


EGG  AND  FEMALE  ORGANS  OF  GENERATION.    549 

absorbs  the  water  in  which,  the  spawn  is  deposited,  and  swells  up 
into  a  transparent  gelatinous  mass,  in  which  the  eggs  are  separately 
imbedded.  This  substance  supplies,  by  its  subsequent  liquefaction 
and  absorption,  a  certain  amount  of  nutritious  material,  durino-  the 
development  and  early  growth  of  the  embryo. 

In  the  terrestrial  reptiles  and  in  birds,  the  oviducts  perform  a 
still  more  important  secretory  function.  In  the  common  fowl,  the 
ovary  consists,  as  in  the  frog,  of  a  large  number  of  follicles,  loosely 
connected  by  areolar  tissue,  in  which  the  eggs  can  be  seen  in  different 
stages  of  development.  (Fig.  180,  a)  As  the  egg  which  is  approach- 
ing  maturity  enlarges,  it  distends  the  cavity  of  its  follicle,  and  pro- 
jects farther  from  the  general  surface  of  the  ovary ;  so  that  it  hangs 
at  last  into  the  peritoneal  cavity,  retained  only  by  the  attenuated 
wall  of  the  follicle,  and  a  slender  pedicle  through  which  run  the 
bloodvessels  by  which  its  circulation  is  supplied.  A  rupture  of  the 
follicle  then  occurs,  at  its  most  prominent  part,  and  the  egg  is  dis- 
charged from  the  lacerated  opening. 

At  the  time  of  its  leaving  the  ovary,  the  Qgg  of  the  fowl  consists 
of  a  large,  globular,  orange-colored  vitellus,  or  "yolk,"  inclosed  in 
a  thin  and  transparent  vitelline  membrane.  Immediately  under- 
neath the  vitelline  membrane,  at  one  point  upon  the  surface  of  the 
vitellus,  is  a  round  white  spot,  consisting  of  a  layer  of  minute 
granules,  termed  the  "  cicatricula."  It  is  in  the  central  part  of  the 
cicatricula  that  the  germinative  vesicle  is  found  imbedded,  at  an 
early  stage  of  the  development  of  the  egg.  At  the  time  of  its 
discharge  from  the  ovary,  the  germinative  vesicle  has  usually  dis- 
appeared ;  but  the  cicatricula  is  still  a  very  striking  and  important 
part  of  the  vitellus,  as  it  is  from  this  spot  that  the  body  of  the  chick 
begins  afterward  to  be  developed. 

At  the  same  time  that  the  egg  protrudes  from  the  surface  of  the 
ovary,  it  projects  into  the  inner  orifice  of  the  oviduct ;  so  that,  when 
discharged  from  its  follicle,  it  is  immediately  embraced  by  the  upper 
or  fringed  extremity  of  this  tube,  and  commences  its  passage  down- 
ward. In  the  fowl,  the  muscular  coat  of  the  oviduct  is  highly  deve- 
loped, and  its  peristaltic  contractions  gently  urge  the  egg  from  above 
downward,  precisely  as  the  oesophagus  or  the  intestines  transport 
the  food  in  a  similar  direction.  While  passing  through  the  first 
two  or  three  inches  of  the  oviduct  (c,  tZ),  where  the  mucous  mem- 
brane is  smooth  and  transparent,  the  yolk  merely  absorbs  a  certain 
quantity  of  fluid,  so  as  to  become  more  flexible  and  yielding  in  con- 
sistency.    It  tbon  passes  into  a  second  division  of  the  generative 


550  EGG    AND    FEilALE    ORGANS    OF    GENERATION. 

canal,  in  which  the  mucous  membrane  is  thick  and  glandular  in 
texture,  and  is  also  thrown  into  numerous  longitudinal  folds,  which 
project  into  the  cavity  of  the  oviduct.  This  portion  of  the  oviduct 
{d,  e),  extends  over  about  nine  inches  of  its  entire  length.  In  its 
upper  part,  the  mucous  membrane  secretes  a  viscid  material,  by 
which  the  yolk  is  encased,  and  which  soon  consolidates  into  a  gela- 
tinous, membranous  deposit ;  thus  forming  a  second  homogeneous 
layer,  outside  the  vitelline  membrane. 

Now  the  peristaltic  movements  of  this  part  of  the  oviduct  are 
such  as  to  give  a  rotary,  as  well  as  a  progressive  motion  to  the 
egg ;  and  the  two  extremities  of  the  membranous  layer  described 
above  become,  accordingly,  twisted  in  opposite  directions  into  two 
fine  cords,  which  run  backward  and  forward  from  the  opposite  poles 
of  the  Qgg.  These  cords  are  termed  the  "  chalazse,"  and  the  mem- 
brane with  which  they  are  connected,  the  "  chalaziferous  membrane." 

Throughout  the  remainder  of  the  second  division  of  the  oviduct, 
the  mucous  membrane  exudes  an  abundant,  gelatinous,  albuminoid 
substance,  which  is  deposited  in  successive  layers  round  the  yolk, 
inclosing  at  the  same  time  the  chalaziferous  membrane  and  the 
chalazas.  This  substance,  which  forms  the  so-called  albumen,  or 
"  white  of  Qgg,^^  is  semi-solid  in  consistency,  nearly  transparent,  and 
of  a  faint  amber  color.  It  is  deposited  in  greater  abundance  in  front 
of  the  advancing  egg  than  behind  it,  and  forms  accordingly  a 
pointed  or  conical  projection  in  front,  while  behind,  its  outline  is 
rounded  off,  parallel  with  the  spherical  surface  of  the  yolk.  In  this 
way,  the  egg  acquires,  when  covered  with  its  albumen,  an  ovoid 
form,  of  which  one  end  is  round,  the  other  pointed ;  the  pointed 
extremity  being  always  directed  downward,  as  the  egg  descends 
along  the  oviduct. 

In  the  third  division  of  the  oviduct  (/),  which  is  about  three  and 
a  half  inches  in  length,  the  mucous  membrane  is  arranged  in  longi- 
tudinal folds,  which  are  narrower  and  more  closely  packed  than  in 
the  preceding  portion.  The  material  secreted  in  this  part,  and  de- 
posited upon  the  egg,  condenses  into  a  firm  fibrous  covering,  com- 
posed of  three  different  layers  which  closely  embrace  the  surface 
of  the  albuminous  mass,  forming  a  tough,  flexible,  semi-opaque 
envelope  for  the  whole.  These  layers  are  known  as  the  external, 
middle,  and  internal  fibrous  membranes  of  the  egg. 

Finally  the  egg  passes  into  the  fourth  division  of  the  oviduct  {g), 
which  is  wider  than  the  rest  of  the  canal,  but  only  a  little  over  two 
inches  in  length.     Here  the  mucous  membrane,  which  is  arranged 


EGG  AND  FEMALE  ORGANS  OF  GENERATION. 


551 


Fig.  180. 


in  abundant,  projecting,  leaf-like  villosities,  exudes  a  fluid  very  rich 
in  calcareous  salts.  The  most  external  of  the  three  membranes 
just  described  is  permeated  by  this  fluid,  and  very  soon  the  calcare- 
ous matter  begins  to  crystallize  in 
the  interstices  of  its  fibres.  This 
deposit  of  calcareous  matter  goes 
on,  growing  constantly  thicker  and 
more  condensed,  until  the  entire 
external  membrane  is  converted  into 
a  white,  opaque,  brittle,  calcareous 
shell,  which  incloses  the  remaining 
portions  and  protects  them  from  ex- 
ternal injury.  The  egg  is  then  driven 
outward  by  the  contraction  of  the 
muscular  coat  through  a  narrow  por- 
tion of  tbe  oviduct  (A),  and,  gradually 
dilating  the  passages  by  its  conical 
extremity,  is  finally  discharged  from 
the  external  orifice. 

The  egg  of  the  fowl,  after  it  has 
been  discharged  from  the  body,  con- 
sists, accordingly,  of  various  parts; 
some  of  which,  as  the  yolk  and  the 
vitelline  membrane,  entered  into  its 
original  formation,  while  the  remain- 
der have  been  deposited  round  it  dur- 
ing its  passage  through  the  oviduct. 
On  examining  such  an  egg  (Fig.  181), 
we  find  externally  the  calcareous 
shell  (A),  while  immediately  beneath 
it  are  situated  the  middle  and  internal 
fibrous  shell-membranes  (e,/). 

Soon  after  the  expulsion  of  the  egg 
there  is  a  partial  evaporation  of  its 
watery  ingredients,  which  are  replaced 
by  air  penetrating  through  the  pores 

F  M  Ai.K  0E5ERATIVE  Oroaks  OF  Fowl. — «.  Ovary,  ft.  Graafian  follicle,  from  which  tli« 
eifg  hat.  just  been  discharged,  c.  Yollc,  entering  upper  extremity  of  oviduct.  rf,e.  Second  divi.-!ioii 
of  oviduct.  In  which  ch:iIa7,iferous  membranf;,  chalazse,  and  albumen  are  formed.  /.  Third  portion, 
in  which  the  flbronn  Khell  membranes  are  produced,  g.  Fourth  portion  laid  open,  showing  enK 
completely  formed,  with  calcareous  sliell.     h.  Narrow  canal  throusjh  which  the  egg  is  discharged. 


552 


EGG  AND  FEMALE  ORGANS  OP  GENERATION. 


of  the  shell  at  its  rounded  extremity.  The  air  thus  introduced 
accumulates  between  the  middle  and  internal  fibrous  membranes 
at  this  spot,  separating  them  from  each  other,  and  forming  a  cavity 
or  air-chamber  {g),  which  is  always  found  between  the  two  fibrous 
membranes  at  the  rounded  end  of  the  Qgg.  Next  we  come  to  the 
albumen  or  "  white"  of  the  eg^  {d) ;  next  to  the  chalaziferous  mem- 
brane and  chalazse  (c) ;  and  finally  to  the  vitelline  membrane  (5) 

Fig.  181. 


Biasrvara  of  Fowl 's  Egg. — ".  Yolk.     J.  Vitelline  membrane,     c.  Chalaziferons  membrane. 
Albumea.     e,  f.  Middle  and  internal  shell  membranes,    g.  Aii-chamber.    h.  Calcareous  shell. 


inclosing  the  yolk  (a).  After  the  expulsion  of  the  egg,  the  external 
layers  of  the  albumen  liquefy ;  and  the  vitellus,  being  specifically 
lighter  than  the  albumen,  owing  to  the  large  proportion  of  oleagin- 
ous matter  which  it  contains,  rises  toward  the  surface  of  the  q^^, 
with  the  cicatricula  uppermost.  This  part,  therefore,  presents 
itself  almost  immediately  on  breaking  open  the  egg  upon  its  lateral 
surface,  and  is  placed  in  the  most  favorable  position  for  the  action 
of  warmth  and  atmospheric  air  in  the  development  of  the  chick. 

The  vitellus,  therefore,  is  still  the  essential  and  constituent  portion 
of  the  egg ;  while  all  the  other  parts  consist  either  of  nutritious  mate- 
rial, like  the  albumen,  provided  for  the  support  of  the  embryo,  or 
of  protective  envelopes,  like  the  shell  and  the  fibrous  membranes. 

In  the  quadrupeds,  another  and  still  more  important  modification 
of  the  oviducts  takes  place.  In  these  animals,  the  q^^,  which  is 
originally  very  minute  in  size,  is  destined  to  b6  retained  within  the 
generative  passages  of  the  female  during  the  development  of  the 
embryo.  While  the  upper  part  of  the  oviduct,  therefore,  is  quite 
narrow,  and  intended  merely  to  transmit  the  egg  from  the  ovary, 


EGG  AND  FEMALE  ORGANS  OF  GENERATION. 


553 


and  to  supply  it  witli  a  little  albuminous  secretion,  its  lower  por- 
tions are  very  much  increased  in  size,  and  are  lined,  moreover,  with 
a  mucous  membrane,  so  constructed  as  to  provide  for  the  protection 
and  nourishment  of  the  embryo,  during  the  entire  period  of  gesta- 
tion. The  upper  and  narrower  portions  of  the  oviduct  are  known 
as  the  "Fallopian  tubes"  (Fig.  182);  while  the  lower  and  more 

Fig.  182. 


TTtertts  and  Ovaries  of  the  Sow.— a,  a.  Ovaries.    b,h.  Fallopian  tubes.    c,c.  Horns  of 
Tiie.  us.    d.  Body  of  uterus,     e.  Vagina. 


highly  developed  portions  constitute  the  uterus.  These  lower  por- 
tions unite  with  each  other  upon  the  median  line  near  their  infe- 
rior termination,  so  as  to  form  a  central  organ,  termed  the  "  body" 
of  the  uterus ;  while  the  remaining  ununited  parts  are  known  as 
its  ''  cornua"  or  "  horns." 

In  the  human  subject,  the  female  generative  apparatus  presents 
the  following  peculiarities.  The  ovaries  consist  of  Graafian  follicles, 
which  are  imbedded  in  a  somewhat  dense  areolar  tissue,  supplied 
with  an  abundance  of  bloodvessels.  The  entire  mass  is  covered 
with  a  thick,  opaque,  yellowish  white  layer  of  fibrous  tissue  called 
the  "  albugineous  tunic."  Over  the  whole  is  a  layer  of  peritoneum, 
which  is  reflected  upon  the  vessels  which  supply  the  ovar^",  and  is 
continuous  with  the  broad  ligaments  of  the  uterus. 

The  oviducts  commence  by  a  wide  expansion,  provided  with 
fringed  edges,  called  the  "  fimbriated  extremity  of  the  Fallopian 
tube."  The  Fallopian  tubes  themselves  are  very  narrow  and  con- 
voluted, and  terminate  on  each  side  in  the  upper  part  of  the  body 
of  the  uterus.  In  the  human  subject,  the  body  of  the  uterus  is  so 
much  developed  at  the  expense  of  the  cornua,  that  the  latter  hardly  , 
appear  to  have  an  existence ;  and  in  fact  no  trace  of  them  is  visible 
externally.     But  on  opening  the  body  of  the  uterus  its  cavity  is 


554 


EGG  AND  FEMALE  ORGANS  OF  GENERATION. 


seen  to  be  nearly  triangular  in  shape,  its  two  superior  angles  run- 
ning out  on  each  side  to  join  the  lower  extremities  of  the  Fallopian 
tubes.  This  portion  evidently  consists  of  the  cornua,  which  have 
been  consolidated  with  the  body  of  the  uterus,  and  enveloped  in 
its  thickened  layer  of  muscular  fibres. 


Fig.  183. 


Generative    Okoaks    op    Human    Female. — n,  a.    Ovaries.     5,  h.  Fallopian    tubes, 
c.  Body  of  uterus,     d.  Cervix.    «.  Vagina. 

The  cavity  of  the  body  of  the  uterus  terminates  below  by  a  con- 
stricted portion  termed  the  os  internum,  by  which  it  is  separated 
from  the  cavity  of  the  cervix.  These  two  cavities  are  not  only 
different  from  each  other  in  shape,  but  differ  also  in  the  structure 
of  their  mucous  membrane  and  the  functions  which  it  is  destined 
to  perform. 

The  mucous  membrane  of  the  body  of  the  uterus  in  its  usual 
condition  is  smooth  and  rosy  in  color,  and  closely  adherent  to  the 
subjacent  muscular  tissue.  It  consists  of  minute  tubular  follicles 
somewhat  similar  to  those  of  the  gastric  mucous  membrane,  ranged 
side  by  side,  and  opening  by  distinct  orifices  upon  its  free  surface. 
The  secretion  of  these  follicles  is  destined  for  the  nutrition  of  the 
embryo  during  the  earlier  periods  of  its  formation. 

The  internal  surface  of  the  neck  of  the  uterus,  on  the  other  hand, 
is  raised  in  prominent  ridges  which  are  arranged  usually  in  two 
lateral  sets,  diverging  from  a  central  longitudinal  ridge ;  presenting 
the  appearance  known  as  the  "  arbor  vitas  uterina."  The  follicles 
of  this  part  of  the  uterine  mucous  membrane  are  different  in  struc- 
ture from  those  of  the  foregoing.     They  are  of  a  globular  or  sac- 


EGG  AND  FEMALE  ORGANS  OF  GENERATION.    555 

like  form,  and  secrete  a  very  firm,  adhesive,  transparent  mucus, 
which  is  destined  to  block  up  the  cavity  of  the  cervix  during  ges- 
tation, and  guard  against  the  accidental  displacement  of  the  egg. 
Some  of  these  follicles  are  frequently  distended  with  their  secretion, 
and  project,  as  small,  hard,  rounded  eminences,  from  the  surface 
of  the  mucous  membrane.  In  this  condition  they  are  sometimes 
designated  by  the  name  of  "  ovula  Nabothi,"  owing  to  their  having 
been  formerly  mistaken  for  eggs,  or  ovules. 

The  cavity  of  the  cervix  uteri  is  terminated  below  by  a  second 
constriction,  the  "os  externum."  Below  this  comes  the  vagina, 
which  constitutes  the  last  division  of  the  female  generative  pas- 
sages. 

The  accessory  female  organs  of  generation  consist  therefore  of 
ducts  or  tubes,  by  means  of  which  the  egg  is  conveyed  from  within 
outward.  These  ducts  vary  in  the  degree  and  complication  of 
their  development,  according  to  the  importance  of  the  task  assigned 
to  them.  In  the  lower  orders,  they  serve  merely  to  convey  the  egg 
rapidly  to  the  exterior,  and  to  supply  it  more  or  less  abundantly 
with  an  albuminous  secretion.  In  the  higher  classes  and  in  the 
human  subject,  they  are  adapted  to  the  more  important  function  of 
retaining  the  egg  during  the  period  of  gestation,  and  of  providing 
during  the  same  time  for  the  nourishment  of  the  young  embryo. 


556  MALE  ORGANS  OF  GENERATION. 


CHAPTER  IV. 

ON  THE  SPERMATIC  FLUID,  AND  THE  MALE 
OEGANS  OF  GENERATION. 

The  mature  egg  is  not  bj  itself  capable  of  being  developed  into 
the  embryo.  If  simply  discharged  from  the  ovary  and  carried 
through  the  oviducts  toward  the  exterior,  it  soon  dies  and  is  de- 
composed, like  any  other  portion  of  the  body  separated  from  its 
natural  connections.  It  is  only  when  fecundated  by  the  spermatic 
fluid  of  the  male,  that  it  is  stimulated  to  continued  development, 
and  becomes  capable  of  a  more  complete  organization. 

The  product  of  the  male  generative  organs  consists  of  a  colorless, 
somewhat  viscid,  and  albuminous  fluid,  containing  an  innumerable 
quantity  of  minute  filamentous  bodies,  termed  spermatozoa.  The 
name  spermatozoa  has  been  given  to  these  bodies,  on  account  of 
their  exhibiting  under  the  microscope  a  very  active  and  continu- 
ous movement,  bearing  some  resemblance  to  that  of  certain  animal- 
cules. 

The  spermatozoa  of  the  human  subject  (Fig.  184,  a)  are  about 
g^^  of  an  inch  in  length,  according  to  the  measurements  of  Kol- 
liker.  Their  anterior  extremity  presents  a  somewhat  flattened, 
triangUlar-shaped  enlargement,  termed  the  "  head."  The  head  con- 
stitutes about  one-tenth  part  the  entire  length  of  the  spermato- 
zoon. The  remaining  portion  is  a  very  slender  filamentous  pro- 
longation, termed  the  "tail,"  which  tapers  gradually  backward, 
becoming  so  exceedingly  delicate  towards  its  extremity,  that  it  is 
difficult  to  be  seen  except  when  in  motion.  There  is  no  further 
organization  or  internal  structure  to  be  detected  in  any  part  of  the 
spermatozoon ;  and  the  whole  appears  to  consist,  so  far  as  can  be 
seen  by  the  microscope,  of  a  completely  homogeneous,  tolerably 
firm,  albuminoid  substance.  The  terms  head  and  tail,  therefore, 
as  justly  remarked  by  Bergmann  and  Leuckart,^  are  not  used, 
when  describing  the  different  parts  of  the  spermatozoon,  in  the 
same  sense  as  that  in  which  they  would  be  applied  to  the  corre- 

'  Vergleichende  Physiologic.     Stuttgart,  1852. 


MALE    ORGANS    OF    GENERATIOIST. 


557 


spending  parts  of  an  animal,  but  simply  for  the  sake  of  conveni- 
ence ;  just  as  one  might  speak  of  the  head  of  an  arrow,  or  the  tail 
of  a  comet. 

In  the  lower  animals,  the  spermatozoa  have  -usually  the  same 
general  form  as  in  the  human  subject;  that  is,  they  are  slender 
filamentous  bodies,  with  the  anterior  extremity  more  or  less  en- 
larged. In  the  rabbit  they  have  a  head  which  is  roundish  and 
flattened  in  shape,  somewhat  resembling  the  globules  of  the  blood. 
In  the  rat  (Fig.  184,  b)  they  are  much  larger  than  in  man,  measur- 
ing nearly  yig  of  an  inch  in  length.     The  head  is  conical  in  shape, 

Fig.  184. 


Spermatozoa. — a.  Human,    b.  Of  Rat.    c.  Of  Menobranchus.    Magnified  480  times. 

about  one-twentieth  the  whole  length  of  the  filament,  and  often 
slightly  curved  at  its  anterior  extremity.  In  the  frog  and  in  rep- 
tiles generally,  the  spermatozoa  are  longer  than  in  quadrupeds. 
In  the  Menobranchus,  or  great  American  water-lizard,  they  are  of 
very  unusual  size  (Fig.  184,  c),  measuring  not  less  than  ^\  of  an 
inch  in  length,  about  one-third  of  which  is  occupied  by  the  head, 
6r  enlarged  portion  of  the  filament. 

The  rno.st  remarkable   peculiarity  of  the  spermatozoa  is  their 


558  MALE  ORGANS  OF  GKNERATION. 

very  singular  and  active  movement,  to  wliich  we  liave  already 
alluded.  If  a  drop  of  fresli  seminal  fluid  be  placed  under  the 
microscope,  the  numberless  minute  filaments  with  which  it  is 
crowded  are  seen  to  be  in  a  state  of  incessant  and  agitated  motion. 
This  movement  of  the  spermatozoa,  in  many  species  of  animals, 
strongly  resembles  that  of  the  tadpole ;  particularly  when,  as  in  the 
human  subject,  the  rabbit,  &c.,  the  spermatozoa  consist  of  a  short 
and  well  defined  head,  followed  by  a  long  and  slender  tail.  Here 
the  tail-like  filament  keeps  up  a  constant  lateral  or  vibratory  move- 
ment, by  which  the  spermatozoon  is  driven  from  place  to  place  in 
the  spermatic  fluid,  just  as  the  fish  or  the  tadpole  is  propelled 
through  the  water.  In  other  instances,  as  for  example  in  the  water- 
lizard,  and  in  some  parasitic  animals,  the  spermatozoa  have  a  con- 
tinuous writhing  or  spiral-like  movement,  which  presents  a  very 
peculiar  and  elegant  appearance  when  large  numbers  of  them  are 
viewed  together. 

It  is  the  existence  of  this  movement  which  first  suggested  the 
name  of  spermatozoa  to  designate  the  animated  filaments  of  the 
spermatic  fluid ;  and  which  has  led  some  writers  to  attribute  to 
them  an  independent  animal  nature.  This  is,  >however,  a  very 
erroneous  mode  of  regarding  them ;  since  they  cannot  properly  be 
considered  as  animals,  notwithstanding  the  active  character  of  their 
movement,  and  the  striking  resemblance  which  it  sometimes  pre- 
sents to  a  voluntary  act.  The  spermatozoa  are  organic  forms, 
which  are  produced  in  the  testicles,  and  constitute  a  part  of  their 
tissue ;  just  as  the  eggs,  which  are  produced  in  the  ovaries,  natu- 
rally form  a  part  of  the  texture  of  these  organs.  Like  the  egg, 
also,  the  spermatozoon  is  destined  to  be  discharged  from  the  organ 
where  it  grew,  and  to  retain,  for  a  certain  length  of  time  afterward, 
its  vital  properties.  One  of  the  most  peculiar  of  these  properties 
is  its  power  of  keeping  in  constant  motion ;  which  does  not,  how- 
ever, mark  it  as  a  distinct  animal,  but  only  distinguishes  it  as  a 
peculiar  structure  belonging  to  the  parent  organism.  The  motion 
of  a  spermatozoon  is  precisely  analogous  to  that  of  a  ciliated  epi- 
thelium cell.  The  movement  of  the  latter  will  continue  for  some 
hours  after  it  has  been  separated  from  its  mucous  membrane,  pro- 
vided its  texture  be  not  injured,  nor  the  process  of  decomposition 
allowed  to  commence.  In  the  same  manner,  the  movement  of  the 
spermatozoa  is  a  characteristic  property  belonging  to  them,  which 
continues  for  a  certain  time,  even  after  they  have  been  separated 
from  the  rest  of  the  body. 


MALE  OKGANS  OF  GENERATION.  559 

III  order  to  preserve  their  vitality,  the  spermatozoa  must  be 
kept  at  the  ordinary  temperature  of  the  body,  and  preserved 
from  the  contact  of  the  air  or  other  unnatural  fluids.  In  this  way, 
they  may-  be  kept  without  difficulty  many  hours  for  purposes  of 
examination.  But  if  the  fluid  in  which  they  are  kept  be  allowed 
to  dry,  or  if  it  be  diluted  by  the  addition  of  water,  in  the  case  of 
birds  and  quadrupeds,  or  if  it  be  subjected  to  extremes  of  heat  or 
cold,  the  motion  ceases,  and  the  spermatozoa  themselves  soon  begin 
to  disintegrate. 

The  spermatozoa  are  produced  in  certain  glandular-looking 
organs,  the  testicles,  which  are  characteristic  of  the  male,  as  the  ova- 
ries are  characteristic  of  the  female.  In  man  and  all  the  higher 
animals,  the  testicles  are  solid,  ovoid-shaped  bodies,  composed 
principally  of  numerous  long,  narrow,  and  convoluted  tubes,  the 
''  seminiferous  tubes,"  somewhat  similar  in  their  general  anatomical 
characters  to  the  tubuli  uriniferi  of  the  kidneys.  These  tubes  lie 
for  the  most  part  closely  in  contact  with  each  other,  so  that  nothing 
intervenes  between  them  except  capillary  bloodvessels  and  a  little 
areolar  tissue.  They  commence,  by  blind,  rounded  extremities,  near 
the  external  surface  of  the  testicle,  and  pursue  an  intricately  con- 
voluted course  toward  its  central  and  posterior  part.  They  are  not 
strongly  adherent  to  each  other,  but  may  be  readily  unravelled  by 
manipulation,  and  separated  from  each  other. 

The  formation  of  the  spermatozoa,  as  it  takes  place  in  the 
substance  of  the  testicle;  has  been  fully  investigated  by  Kdlliker. 
According  to  his  observations,  as  the  age  of  puberty  approaches, 
beside  the  ordinary  pavement  epithelium  lining  the  seminiferous 
tubes,  other  cells  or  vesicles  of  larger  size  make  their  appearance 
in  these  tubes,  each  containing  from  one  to  fifteen  or  twenty  nuclei, 
with  nucleoli.  It  is  in  the  interior  of  these  vesicles  that  the  sper- 
matozoa are  formed ;  their  number  corresponding  usually  with  that 
of  the  nuclei  just  mentioned.  They  are  at  first  developed  in  bundles 
of  ten  to  twenty,  held  together  by  the  thin  membranous  substance 
which  surrounds  them,  but  are  afterward  SQt  free  by  the  liquefac- 
tion of  the  vesicle,  and  then  fill  nearly  the  entire  cavity  of  the 
seminiferous  ducts,  mingled  only  with  a  very  minute  quantity  of 
transparent  fluid. 

In  the  seminiferous  tubes  themselves,  the  spermatozoa  are  al- 
ways inclosed  in  the  interior  of  their  parent  vesicles ;  they  are  libe- 
rated, and  mingled  promiscuously  together,  only  after  entering  the 
rete  testis  and  the  head  of  the  epididymis. 


560  MALE  OKGANS  OF  GENERATION. 

Beside  the  testicles,  whicli  are,  as  above  stated,  the  primary  and 
essential  parts  of  the  male  generative  apparatus,  there  are  certain 
secondary  or  accessory  organs,  by  means  of  which  the  spermatic 
fluid  is  conveyed  to  the  exterior,  and  mingled  with  various  secre- 
tions which  assist  in  the  accomplishment  of  its  functions. 

As  the  sperm  leaves  the  testicle,  it  consists,  as  above  mentioned, 
almost  entirely  of  the  spermatozoa,  crowded  together  in  an  opaque, 
white,  semi-fluid  mass,  which  fills  up  the  vasa  efl'erentia,  and  com- 
pletely distends  their  cavities.  It  then  enters  the  single  duct 
which  forms  the  body  and  lower  extremity  of  the  epididymis, 
following  the  long  and  tortuous  course  of  this  tube,  until  it 
reaches  the  vas  deferens;  through  which  it  is  still  conveyed 
onward  to  the  point  where  this  canal  opens  into  the  urethra. 
Throughout  this  course,  it  is  mingled  with  a  glairy,  mucus-like 
fluid,  secreted  by  the  walls  of  the  epididymis  and  vas  deferens,  in 
which  the  spermatozoa  are  enveloped.  The  mixture  is  then  depo- 
sited in  the  vesiculse  seminales,  where  it  accumulates,  as  fresh  quan- 
tities are  produced  in  the  testicle  and  conveyed  downward  by  the 
spermatic  duct.  It  is  probable  that  a  second  secretion  is  supplied 
also  by  the  internal  surface  of  the  vesiculse  seminales,  and  that  the 
sperm,  while  retained  in  their  cavities,  is  not  only  stored  up  for 
subsequent  use,  but  is  at  the  same  time  modified  in  its  properties 
by  the  admixture  of  another  fluid. 

At  the  time  when  the  evacuation  of  the  sperm  takes  place,  it  is 
driven  out  from  the  seminal  vesicles  by  the  muscular  contraction 
of  the  surrounding  parts,  and  meets  in  the  urethra  with  the  secre- 
tions of  the  prostate  gland,  the  glands  of  Cowper,  and  the  mucous 
follicles  opening  into  the  urethral  passage.  All  these  organs  are  at 
that  time  excited  to  an  unusual  activity  of  secretion,  and  pour  out 
their  difierent  fluids  in  great  abundance. 

The  sperm,  therefore,  as  it  is  discharged  from  the  urethra,  is  an 
exceedingly  mixed  fluid,  consisting  of  the  spermatozoa  derived 
from  the  testicles,  together  with  the  secretions  of  the  epididymis 
and  vas  deferens,  the  prostate,  Cowper's  glands,  and  the  mucous  fol- 
licles of  the  urethra.  Of  all  these  ingredients,  it  is  the  spermatozoa 
which  constitute  the  essential  part  of  the  seminal  fluid.  They  are 
the  true  fecundating  element  of  the  sperm,  while  all  the  others  are 
secondary  in  importance,  and  perform  only  accessory  functions. 

Spallanzani  found  that  if  frog's  semen  be  passed  through  a  suc- 
cession of  filters,  so  as  to  separate  the  spermatozoa  from  the  liquid 
portions,  the  filtered  fluid  is  destitute  of  any  fecundating  properties ; 


MALE  OEGANS  OF  GENERATION.  561 

while  tlie  spermatozoa  remaining  entangled  in  the  filter,  if  mixed 
with  a  sufficient  quantity  of  fluid  of  the  requisite  density  for  dilu- 
tion, may  still  be  successfully  used  for  the  impregnation  of  eggs. 
It  is  well  known,  also,  that  animals  or  men  from  whom  both  testi- 
cles have  been  removed,  are  incapable  of  impregnating  the  female 
or  her  eggs ;  while  a  removal  or  imperfection  of  any  of  the  other 
generative  organs  does  not  necessarily  prevent  the  accomplishment 
of  the  function. 

In  most  of  the  lower  orders  of  animals  there  is  a  periodical 
development  of  the  testicles  in  the  male,  corresponding  in  time  with 
that  of  the  ovaries  in  the  female.  As  the  ovaries  enlarge  and  the 
eggs  ripen  in  the  one  sex,  so  in  the  other  the  testicles  increase  in 
size,  as  the  season  of  reproduction  approaches,  and  become  turgid 
with  spermatozoa.  The  accessory  organs  of  generation,  at  the 
same  time,  share  the  unusual  activity  of  the  testicles,  and  become 
increased  in  vascularity  and  ready  to  perform  their  part  in  the 
reproductive  function. 

In  the  fish,  for  example,  where  the  testicles  occupy  the  same 
position  in  the  abdomen  as  the  ovaries  in  the  opposite  sex,  these 
bodies  enlarge,  become  distended  with  their  contents,  and  project 
into  the  peritoneal  cavity.  Each  of  the  two  sexes  is  then  at  the 
same  time  under  the  influence  of  a  corresponding  excitement.  The 
unusual  development  of  the  generative  organs  reacts  upon  the  entire 
system,  and  produces  a  state  of  peculiar  activity  and  excitabilityj 
known  as  the  condition  of  "  erethism,"  The  female,  distended  with 
eggs,  feels  the  impulse  which  leads  to  their  expulsion ;  while  the 
male,  bearing  the  weight  of  the  enlarged  testicles  and  the  accumu- 
lation of  newly-developed  spermatozoa,  is  impelled  by  a  similar 
sensation  to  the  discharge  of  the  spermatic  fluid.  The  two  sexes, 
accordingly,  are  led  by  instinct  at  this  season  to  frequent  the  same 
situations.  The  female  deposits  her  eggs  in  some  spot  favorable 
to  the  protection  and  development  of  the  young ;  after  which  the 
male,  apparently  attracted  and  stimulated  by  the  sight  of  the  new- 
laid  eggs,  discharges  the  spermatic  fluid  upon  them,  and  their 
impregnation  is  accomplished. 

In  such  instances  as  the  above,  where  the  male  and  female  gene- 
rative products  are  discharged  separately  by  the  two  sexes,  the 
subsequent  contact  of  the  eggs  with  the  spermatic  fluid  would  seem 
to  be  altogether  dependent  on  the  occurrence  of  fortuitous  circum- 
stances, and  their  impregnation,  therefore,  often  liable  to  fail.  In 
point  of  fact,  however,  the  simultaneous  functional  excitement  of 
36 


662  MALE  ORGANS  OP  GENERATION". 

the  two  sexes  and  the  operation  of  corresponding  instincts,  leading 
them  to  ascend  the  same  rivers  and  to  frequent  the  same  spots, 
provide  with  sufi&cient  certainty  for  the  impregnation  of  the  eggs. 
In  these  animals,  also,  the  number  of  eggs  produced  by  the  female 
is  very  large,  the  ovaries  being  often  so  distended  as  to  fill  nearly 
the  whole  of  the  abdominal  cavity ;  so  that,  although  many  of  the 
eggs  may  be  accidentally  lost,  a  sufficient  number  will  still  be  im- 
pregnated and  developed,  to  provide  for  the  continuation  of 'the 
species. 

In  other  instances,  an  actual  contact  takes  place  between  the 
sexes  at  the  time  of  reproduction.  In  the  frog,  for  example,  the 
male  fastens  himself  upon  the  back  of  the  female  by  the  anterior 
extremities,  which  seem  to  retain  their  hold  by  a  kind  of  spasmodic 
contraction.  This  continues  for  one  or  two  days,  during  which 
time  the  mature  eggs,  which  have  been  discharged  from  the  ovary, 
are  passing  downward  through  the  oviducts.  At  last  they  are  ex- 
pelled from  the  anus,  while  at  the  same  time  the  seminal  fluid  of 
the  male  is  discharged  upon  them,  and  impregnation  takes  place. 

In  the  higher  classes  of  animals,  however,  and  in  man,  where  the 
egg  is  to  be  retained  in  the  body  of  the  female  parent  during  its 
development,  the  spermatic  fluid  is  introduced  into  the  female 
generative  passages  by  sexual  congress,  and  meets  the  egg  at  or 
soon  after  its  discharge  from  the  ovary.  The  same  correspondence, 
however,  between  the  periods  of  sexual  excitement  in  the  male  and 
female,  is  visible  in  many  of  these  animals,  as  well  as  in  fish  and 
reptiles.  This  is  the  case  in  most  species  which  produce  young  but 
once  a  year,  and  at  a  fixed  period,  as  the  deer  and  the  wild  hog.  In 
other  species,  on  the  contrary,  such  as  the  dog,  as  well  as  the  rabbit, 
the  guinea  pig,  &c.,  where  several  broods  of  young  are  produced 
during  the  year,  or  where,  as  in  the  human  subject,  the  generative 
epochs  of  the  female  recur  at  short  intervals,  so  that  the  particular 
period  of  impregnation  is  comparatively  indefinite,  the  generative 
apparatus  of  the  male  is  almost  constantly  in  a  state  of  full  deve- 
lopment ;  and  is  excited  to  action  at  particular  periods,  apparently 
by  some  influence  derived  from  the  condition  of  the  female. 

In  the  quadrupeds,  accordingly,  and  in  the  human  species,  the 
contact  of  the  sperm  with  the  egg  and  the  fecundation  of  the  latter 
take  place  in  the  generative  passages  of  the  female ;  either  in  the 
uterus,  the  Fallopian  tubes,  or  even  upon  the  surface  of  the  ovary ; 
in  each  of  which  situations  the  spermatozoa  have  been  found,  after 
the  accomplishment  of  sexual  intercourse. 


PEBIODICAL    OVULATION.  563 


CHAPTER  V. 

ON   PERIODICAL    OVULATION,   AND    THE    FUNCTION 
OF   MENSTRUATIO 


I.  PERIODICAL  OVULATION. 

"We  have  already  spoken  in  general  terms  of  the  periodical  ripen- 
ing of  the  eggs  and  their  discharge  from  the  generative  organs  of 
the  female.  This  function  is  known  by  the  name  of  "  ovulation," 
and  may  be  considered  as  the  primary  and  most  important  act  in 
the  process  of  reproduction.  We  shall,  therefore,  enter  more  fully 
into  the  consideration  of  certain  particulars  in  regard  to  it,  by 
which  its  nature  and  conditions  may  be  more  clearly  understood. 

1st.  Sggs  exist  originally  in  the  ovaries  of  all  animals,  as  part  of 
their  natural  structure.  In  describing  the  ovaries  of  fish  and  reptiles 
we  have  said  that  they  consist  of  nothing  more  than  Graafian  vesi- 
cles, each  vesicle  containing  an  Qgg,  and  united  with  the  others  by 
loose  areolar  tissue  and  a  peritoneal  investment.  In  the  higher 
animals  and  in  the  human  subject,  the  essential  constitution  of  the 
ovary  is  the  same ;  only  its  fibrous  tissue  is  more  abundant,  so  that 
the  texture  of  the  entire  organ  is  more  dense,  and  its  figure  more 
compact.  In  all  classes,  however,  without  exception,  the  interior 
of  each  Graafian  vesicle  is  occupied  by  an  egg ;  and  it  is  from  this 
Qgg  that  the  young  offspring  is  afterward  produced. 

The  process  of  reproduction  was  formerly  regarded  as  essentially 
different  in  the  oviparous  and  the  viviparous  animals.  In  the  ovipa- 
rous classes,  such  as  most  fish,  and  all  reptiles  and  birds,  the  young 
animal  was  well  known  to  be  formed  from  an  egg  produced  by  the 
female ;  while  in  the  viviparous  animals,  or  those  which  bring 
forth  their  young  alive,  such  as  the  quadrupeds  and  the  human 
species,  the  embryo  was  supposed  to  originate  in  the  body  of  the 
female,  by  some  altogether  peculiar  and  mysterious  process,  m 
consequence  of  sexual  intercourse.  As  soon,  however,  as  the 
microscope  began  to  be  used  in  the  examination  of  the  tissues, 


564       OVULATION   AND    FUNCTION    OF    MENSTRUATION. 

the  ovaries  of  quadrupeds  were  also  found  to  contain  eggs.  These 
eggs  bad  previously  escaped  observation  on  account  of  their  simple 
structure  and  minute  size ;  but  they  were  nevertheless  found  to 
possess  all  the  most  essential  characters  belonging  to  the  larger 
eggs  of  the  oviparous  animals. 

The  true  difference  in  the  process  of  reproduction,  between  the 
two  classes,  is  therefore  merely  an  apparent,  not  a  fundamental  one. 
In  fish,  reptiles,  and  birds,  the  egg  is  discharged  by  the  female 
before  or  immediately  after  impregnation,  and  the  embryo  is  subse- 
quently developed  and  hatched  externally.  In  the  quadrupeds  and 
the  human  species,  on  the  other  hand,  the  egg  is  retained  within 
the  body  of  the  female  until  the  embryo  is  developed ;  when  the 
membranes  are  ruptured  and  the  young  expelled  at  the  same  time. 
In  all  classes,  however,  viviparous  as  well  as  oviparous,  the  young 
is  produced  equally  from  an  egg ;  and  in  all  classes  the  egg,  some- 
times larger  and  sometimes  smaller,  but  always  consisting  essentially 
of  a  vitellus  and  a  vitelline  membrane,  is  contained  originally  in 
the  interior  of  an  ovarian  follicle. 

The  egg  is  accordingly,  as  we  have  already  intimated,  an  integral 
part  of  the  ovarian  tissue.  It  may  be  found  there  long  before  the 
generative  function  is  established,  and  during  the  earliest  periods 
of  life.  It  may  be  found  without  difficulty  in  the  newly  born 
female  infant,  and  may  even  be  detected  in  the  foetus  before  birth. 
Its  growth  and  nutrition,  also,  are  provided  for  in  the  same  man- 
ner with  that  of  other  portions  of  the  bodily  structure, 

2d.  These  eggs  become  more  fully  developed  at  a  certain  age,  when 
tlue  generative  function  is  about  to  be  established.  During  the  early 
periods  of  life,  the  ovaries  and  their  contents,  like  many  other 
organs,  are  imperfectly  developed.  They  exist,  but  they  are  as 
yet  inactive,  and  incapable  of  performing  any  function.  In  the 
young  chick,  for  example,  the  ovary  is  of  small  size ;  and  the  eggs, 
instead  of  presenting  the  voluminous,  yellow,  opaque  vitellus  which 
they  afterward  exhibit,  are  minute,  transparent,  and  colorless.  In 
the  young  quadrupeds,  and  in  the  human  female  during  infancy 
and  childhood,  the  ovaries  are  equally  inactive.  They  are  small, 
friable,  and  of  a  nearly  homogeneous  appearance  to  the  naked  eye ; 
presenting  none  of  the  enlarged  follicles,  filled  with  transparent 
fluid,  which  are  afterward  so  readily  distinguished.  At  this  time, 
accordingly,  the  female  is  incapable  of  bearing  young,  because  the 
ovaries  are  inactive,  and  the  eggs  which  they  contain  immature. 

At  a  certain  period,  however,  which  varies  in  the  time  of  its 


PERIODICAL   OVULATIOIT.  565 

occurrence  for  different  species  of  animals,  the  sexual  apparatus 
begins  to  enter  upon  a  state  of  activity.  The  ovaries  increase  in 
size,  and  their  circulation  becomes  more  active.  The  eggs,  also, 
instead  of  remaining  quiescent,  take  on  a  rapid  growth,  and  the 
structure  of  the  vitellus  is  completed  bj  the  abundant  deposit  of 
oleaginous  granules  in  its  interior.  Arrived  at  this  state,  the  eggs 
are  ready  for  impregnation,  and  the  female  becomes  capable  of 
bearing  young.  She  is  then  said  to  have  arrived  at  the  state  of 
"puberty,"  or  that  condition  in  which  the  generative  organs  are 
fully  developed.  This  condition  is  accompanied  by  a  visible 
alteration  in  the  system  at  large,  which  indicates  the  complete 
development  of  the  entire  organism.  In  many  birds,  for  example, 
the  plumage  assumes  at  this  period  more  varied  and  brilliant 
colors;  and  in  the  common  fowl  the  comb,  or  "crest,"  enlarges 
and  becomes  red  and  vascular.  In  the  American  deer  (Cervus 
virginianus),  the  coat,  which  during  the  first  year  is  mottled  with 
white,  becomes  in  the  second  year  of  a  uniform  tawny  or  reddish 
tinge.  In  nearly  all  species,  the  limbs  become  more  compact  and 
the  body  more  rounded ;  and  the  whole  external  appearance  is  so 
altered,  as  to  indicate  that  the  animal  has  arrived  at  the  period  of 
puberty,  and  is  capable  of  reproduction. 

3d.  Successive  crops  of  eggs,  in  the  adult  female,  ripen  and  are 
discharged  independently  of  sexual  intercourse.  It  was  formerly  sup- 
posed, as  we  have  mentioned  above,  that  in  the  viviparous  animals 
the  germ  was  formed  in  the  body  of  the  female  only  as  a  conse- 
quence of  sexual  intercourse.  Even  after  the  important  fact 
became  known  that  eggs  exist  originally  in  the  ovaries  of  these 
animals,  and  are  only  fecundated  by  the  influence  of  the  sperm- 
atic fluid,  the  opinion  still  prevailed  that  the  occurrence  of  sexual 
intercourse  was  the  cause  of  their  being  discharged  from  the  ovary, 
and  that  the  rupture  of  a  Graafian  vesicle  in  this  organ  was  a 
certain  indication  that  coitus  had  taken  place. 

This  opinion,  however,  was  altogether  unfounded.  We  already 
know  that  in  fish  and  reptiles  the  mature  eggs  not  only  leave  the 
ovary,  but  are  actually  discharged  from  the  body  of  the  female 
while  still  unimpregnated,  and  only  subsequently  come  in  contact 
with  the  spermatic  fluid.  In  fowls,  also,  it  is  a  matter  of  common 
observation  that  the  hen  will  continue  to  lay  fully-formed  eggs,  if 
well  supplied  with  nourishment,  without  the  presence  of  the  cock ; 
only  these  eggs,  being  unimpregnated,  are  incapable  of  producing 


566       OVULATION    AND    FUNCTION    OF    MENSTRUATION. 

chicks.  In  oviparous  animals,  therefore,  the  discharge  of  the  egg, 
as  well  as  its  formation,  is  independent  of  sexual  intercourse. 

Continued  observation  shows  this  to  be  the  case,  also,  in  the 
viviparous  quadrupeds.  The  researches  of  Bischoff,  Pouchet,  and 
Coste  have  demonstated  that  in  the  sheep,  the  pig,  the  bitch,  the 
rabbit,  &c.,  if  the  female  be  carefully  kept  from  the  male  until  after 
the  period  of  puberty  is  established,  and  then  killed,  examination 
of  the  ovaries  will  show  that  Graafian  vesicles  have  matured,  rup- 
tured, and  discharged  their  eggs,  in  the  same  manner  as  though 
sexual  intercourse  had  taken  place.  Sometimes  the  vesicles  are 
found  distended  and  prominent  upon  the  surface  of  the  ovary; 
sometimes  recently  ruptured  and  collapsed ;  and  sometimes  in  vari- 
ous stages  of  cicatrization  and  atrophy.  Bischoff,*  in  several  in- 
stances of  this  kind,  actually  found  the  unimpregnated  eggs  in  the 
oviduct,  on  their  way  to  the  cavity  of  the  uterus.  In  those  animals 
in  which  the  ripening  of  the  eggs  takes  place  at  short  intervals,  as, 
for  example,  the  sheep,  the  pig,  and  the  cow,  it  is  very  rare  to  exa- 
mine the  ovaries  in  any  instance  where  traces  of  a  more  or  less 
recent  rupture  of  the  Graafian  follicles  are  not  distinctly  visible. 

One  of  the  most  important  facts,  derived  from  the  examination 
of  such  cases  as  the  above,  is  that  the  ovarian  eggs  become  deve- 
loped and  are  discharged  in  successive  crops,  which  follow  each 
other  regularly  at  periodical  intervals.  If  we  examine  the  ovary 
of  the  fowl,  for  example  (Fig.  180),  we  see  at  a  glance  how  the  eggs 
grow  and  ripen,  one  after  the  other,  like  fruit  upon  a  vine.  In  this 
instance,  the  process  of  evolution  is  very  rapid ;  and  it  is  easy  to 
distinguish,  at  the  same  time,  eggs  which  are  almost  microscopic  in 
size,  colorless,  and  transparent;  those  which  are  larger,  firmer, 
somewhat  opaline,  and  yellowish  in  hue ;  and  finally  those  which 
are  fully  developed,  opaque,  of  a  deep  orange  color,  and  just  ready 
to  leave  the  ovary. 

It  will  be  observed  that  in  this  instance  the  difference  between 
the  undeveloped  and  the  mature  eggs  consists  principally  in  the 
size  of  the  vitellus,  which  is  furthermore,  for  reasons  previously 
given  (Chap.  III.),  very  much  larger  than  in  the  quadrupeds.  It 
is  also  seen  that  it  is  the  increased  size  of  the  vitellus  alone,  by 
which  the  ovarian  follicle  is  distended  and  ruptured,  and  the  egg 
finally  discharged. 

■  Memoire  sur  la  chute  periodique  de  I'oeuf,  &c.,  Annales  des  Sciences  Naturelles, 
Aout — Septembre,  1844. 


PERIODICAL    OVULATION".  567 

In  tlie  "human  species  and  the  quadrupeds,  on  the  otTier  hand, 
the  microscopic  egg  never  becomes  large  enough  to  distend  the 
follicle  bj  its  own  size.  The  rupture  of  the  follicle  and  the  libera- 
tion of  the  egg  are  accordingly  provided  for,  in  these  instances,  by 
a  totally  different  mechanism. 

In  the  earlier  periods  of  life,  in  man  and  the  higher  animals,  the 
egg  is  contained  in  a  Graafian  follicle  which  closely  embraces  its 
exterior,  and  is  consequently  hardly  larger  than  the  egg  itself.  As 
puberty  approaches,  those  follicles  which  are  situated  near  the  free 
surface  of  the  ovary  become  enlarged  by  the  accumulation  of  a 
colorless  serous  fluid  in  their  cavity.  We  then  find  that  the  ovary, 
when  cut  open,  shows  a  considerable  number  of  globular,  transpa- 
rent vesicles,  readily  perceptible  by  the  eye,  the  smaller  of  which 
are  deep  seated,  but  which  increase  in  size  as  they  approach  the 
free  surface  of  the  organ.  These  vesicles  are  the  Graafian  follicles, 
which,  in  consequence  of  the  advancing  maturity  of  the  eggs  con- 
tained in  them,  gradually  enlarge  as  the  period  of  generation  ap- 
proaches. 

The  Graafian  follicle  at  this  time  consists  of  a  closed  globular 
sac  or  vesicle,  the  external  wall  of  which,  though  quite  translucent, 
has  a  fibrous  texture  under  the  microscope  and  is  well  supplied 
with  bloodvessels.  This  fibrous  and  vascular  wall  is  distinguished 
by  the  name  of  the  "membrane  of  the  vesicle."  It  is  not  very 
firm  in  texture,  and  if  roughly  handled  is  easily  ruptured. 

The  membrane  of  the  vesicle  is  lined  throughout  by  a  thin  layer 
of  minute  granular  cells,  which  form  for  it  a  kind  of  epithelium, 
similar  to  the  epithelium  of  the  pleura,  pericardium,  and  other 
serous  membranes.  This  layer  is  termed  the  membrana  granulosa. 
It  adheres  but  slightly  to  the  membrane  of  the  vesicle,  and  may 
easily  be  detached  by  careless  manipulation  before  the  vesicle  is 
opened,  being  then  mingled,  in  the  form  of  light  flakes  and  shreds, 
with  the  serous  fluid  contained  in  the  vesicle. 

At  the  most  superficial  part  of  the  Graafian  follicle,  or  that 
which  is  nearest  the  surface  of  the  ovary,  the  membrana  granulosa 
is  thicker  than  elsewhere.  Its  cells  are  here  accumulated,  in  a 
kind  of  mound  or  "heap,"  which  has  received  the  name  of  the 
curaulus  proligerus.  It  is  sometimes  called  the  discus  proligerus, 
because  the  thickened  mass,  when  viewed  from  above,  has  a  some- 
what circular  or  disk-like  form.  In  the  centre  of  this  thickened 
portion  of  the  membrana  granulosa  the  Qgg  is  imbedded.     It  is 


568       OVULATION   AND   FUNCTION    OF    MENSTRUATION. 


accordingly  always  situated  at  the  most  superficial  portion  of  the 
follicle,  and  advances  in  this  way  toward  the  surface  of  the  ovary. 
As  the  period  approaches  at  which  the  egg  is  destined  to  be  dis- 
charged, the  Graafian  follicle  becomes  more  vascular,  and  enlarges 
by  an  increased  exudation  of  serum  into  its  cavity.     It  then  begins 

Fig.  185. 


Graafian  Follicle,  near  the  period  of  rupture — a.  Membrane  of  the  vesicle,  b.  Membrsna 
grauulosa.  c.  Cavity  of  follicle,  d.  Egg.  e.  Peritoneum.  /.  Tunica  albuginea.  g,  g.  Tissue  of 
the  ovary. 

to  project  from  the  surface  of  the  ovary,  still  covered  by  the  albu- 
gineous  tunic  and  the  peritoneum.  (Fig.  185.)  The  constant  accu- 
mulation of  fluid,  however,  in  the  follicle,  exerts  such  a  steady  and 
increasing  pressure  from  within  outward,  that  the  albugineous  tunic 
and  the  peritoneum  successively  yield  before  it ;  until  the  Graafian 
follicle  protrudes  from  the  ovary  as  a  tense,  rounded,  translucent 

vesicle,  in  which  the  sense  of 
^^'  fluctuation  can  be  readily  per- 

/t  ceived  on  applying  the  fingers 
to  its  surface.  Finally,  the  pro- 
cess of  effusion  and  distension 
still  going  on,  the  wall  of  the 
vesicle  yields  at  its  most  promi- 
nent portion,  the  contained  fluid 
is  driven  out  with  a  gush,  by  the 
reaction  and  elasticity  of  the 
neighboring  ovarian  tissues,  car- 
rying with  it  the  Qgg,  still  en- 
tangled in  the  cells  of  the  pro- 
ligerous  disk. 

The  rupture  of  the  Graafian 
vesicle  is  accompanied,  in  some  instances,  by  an  abundant  hemor-. 


OvAKY  WITH  Graafian  Follicle 
ruptured:  at  a,  e^g  just  discharged  with  a 
portion  of  membraua  granulosa. 


PERIODICAL    OVULATION.  569 

rhage,  whicli  takes  place  from  the  internal  surface  of  the  congested 
follicle,  and  by  which,  its  cavity  is  filled  with  blood.  This  occurs 
in  the  human  subject  and  in  the  pig,  and  to  a  certain  extent,  also,  in 
other  of  the  lower  animals.  Sometimes,  as  in  the  cow,  where  no 
hemorrhage  takes  place,  the  Graafian  vesicle  when  ruptured 
simply  collapses ;  after  which  a  slight  exudation,  more  or  less  tinged 
with  blood,  is  poured  out  during  the  course  of  a  few  hours. 

Notwithstanding,  however,  these  slight  variations,  the  expulsion 
of  the  egg  takes  place,  in  the  higher  animals,  always  in  the  manner 
above  described,  viz.,  by  the  accumulation  of  serous  fluid  in  the 
cavity  of  the  Grraafian  follicle,  by  which  its  walls  are  gradually  dis- 
tended and  finally  ruptured. 

This  process  takes  place  in  one  or  more  Graafian  follicles  at  a 
time,  according  to  the  number  of  young  which  the  animal  produces 
at  a  birth.  In  the  bitch  and  the  sow,  where  each  litter  consists  of 
from  six  to  twenty  young  ones,  a  similar  number  of  eggs  ripen  and 
are  discharged  at  each  period.  In  the  mare,  in  the  cow,  and  in  the 
human  female,  where  there  is  usually  but  one  foetus  at  a  birth,  the 
eggs  are  matured  singly,  and  the  Graafian  vesicles  ruptured,  one 
after  another,  at  successive  periods  of  ovulation. 

4th.  The  ripening  and  discharge  of  the  egg  are  accomjjanied  by  a 
peculiar  condition  of  the  entire  system,  known  as  the  "  rutting''''  condi- 
tion,- or  "  oestruationr  The  peculiar  congestion  and  functional 
activity  of  the  ovaries  at  each  period  of  ovulation,  act  by  sympathy 
upon  the  other  generative  organs  and  produce  in  them  a  greater  or 
less  degree  of  excitement,  according  to  the  particular  species  of  ani- 
mal. Almost  always  there  is  a  certain  amount  of  congestion  of  the 
entire  generative  apparatus;  Fallopian  tubes,  uterus,  vagina,  and 
external  organs.  The  secretions  of  the  vagina  and  neighboring 
parts  are  more  particularly  affected,  being  usually  increased  in  quan- 
tity  and  at  the  same  time  altered  in  quality.  In  the  bitch,  the 
vaginal  mucous  membrane  becomes  red  and  tumefied,  and  pours 
out  an  abundant  secretion  which  is  often  more  or  less  tinged  with 
blood.  The  secretions  acquire  also  at  this  time  a  peculiar  odor, 
which  appears  to  attract  the  male,  and  to  excite  in  him  the  sexual 
impulse.  An  unusual  tumefaction  and  redness  of  the  vagina  and 
vulva  are  also  very  perceptible  in  the  rabbit ;  and  in  some  species 
of  apes  it  has  been  observed  that  these  periods  are  accompanied 
not  only  by  a  bloody  discharge  from  the  vulva,  but  also  by  an  en- 
gorgement and  infiltration  of  the  neighboring  parts,  extending  even 


570       OVULATION    AND    FUNCTION    OF    MENSTRUATION. 

to  the  skin  of  the  buttocks,  the  thighs,  and  the  under  part  of  the 
tail^ 

The  system  at  large  is  also  visibly  affected  by  the  process  going 
on  in  the  ovary.  In  the  cow,  for  example,  the  approach  of  an 
cestrual  period  is  marked  by  an  unusual  restlessness  and  agitation, 
easily  recognized  by  an  ordinary  observer.  The  animal  partially 
loses  her  appetite.  She  frequently  stops  browsing,  looks  about  un- 
easily, perhaps  runs  from  one  side  of  the  field  to  the  other,  and  then 
recommences  feeding,  to  be  disturbed  again  in  a  similar  manner 
after  a  short  interval.  Her  motions  are  rapid  and  nervous,  and  her 
hide  often  rough  and  disordered ;  and  the  whole  aspect  of  the  ani- 
mal indicates  the  presence  of  some  unusual  excitement.  After  this 
condition  is  fully  established,  the  vaginal  secretions  show  them- 
selves in  unusual  abundance,  and  so  continue  for  one  or  two  days ; 
after  which  the  symptoms,  both  local  and  general,  subside  sponta- 
neously, and  the  animal  returns  to  her  usual  condition. 

It  is  a  remarkable  fact,  in  this  connection,  that  the  female  of 
these  animals  will  allow  the  approaches  of  the  male  only  during  and 
immediately  after  the  cestrual  period  ;  that  is,  just  when  the  egg  is 
recently  discharged,  and  ready  for  impregnation.  At  other  times, 
when  sexual  intercourse  would  be  necessarily  fruitless,  the  instinct 
of  the  animal  leads  her  to  avoid  it ;  and  the  concourse  of  the  sexes 
is  accordingly  made  to  correspond  in  time  with  the  maturity  of  the 
egg  and  its  aptitude  for  fecundation. 

II.  MENSTRUATION. 

In  the  human  female,  the  return  of  the  period  of  ovulation  is 
marked  by  a  peculiar  group  of  phenomena  which  are  known  as 
menstruation,  and  which  are  of  sufficient  importance  to  be  described 
by  themselves. 

During  infancy  and  childhood  the  sexual  system,  as  we  have 
mentioned  above,  is  inactive.  No  discharge  of  eggs  takes  place 
from  the  ovaries,  and  no  external  phenomena  show  themselves, 
connected  with  the  reproductive  function. 

At  the  age  of  fourteen  or  fifteen  years,  however,  a  change  begins 
to  manifest  itself.  The  limbs  become  rounder,  the  breasts  increase 
in  size,  and  the  entire  aspect  undergoes  a  peculiar  alteration,  which 
indicates  the  approaching  condition  of  maturity.  At  the  same 
time  a  discharge  of  blood  takes  place  from  the  generative  passages, 

'  Pouchet,  Theorie  positive  de  I'ovulation,  &c.     Paris,  1847,  p.  230. 


MENSTRUATION.  571 

accompanied  by  some  disturbance  of  the  general  system,  and  the 
female  is  then  known  to  have  arrived  at  the  period  of  puberty. 

Afterward,  the  bloody  discharge  just  spoken  of  returns  at  regular 
intervals  of  four  weeks ;  and,  on  account  of  this  recurrence  corres- 
ponding with  the  passage  of  successive  lunar  months,  its  phenomena 
are  designated  by  the  name  of  the  "menses"  or  the  "menstrual 
periods."  The  menses  return  with  regularity,  from  the  time  of 
their  first  appearance,  until  the  age  of  about  forty-five  years. 
During  this  period,  the  female  is  capable  of  bearing  children,  and 
sexual  intercourse  is  liable  to  be  followed  by  pregnancy.  After 
the  forty-fifth  year,  the  periods  first  become  irregular,  and  then 
cease  altogether ;  and  their  final  disappearance  is  an  indication  that 
the  woman  is  no  longer  fertile,  and  that  pregnancy  cannot  again 
take  place. 

Even  during  the  period  above  referred  to,  from  the  age  of  fifteen 
to  forty-five,  the  regularity  and  completeness  of  the  menstrual 
periods  indicate  to  a  great  extent  the  aptitude  of  individual  females 
for  impregnation.  It  is  well  known  that  all  those  causes  of  ill 
health  which  derange  menstruation  are  apt  at  the  same  time  to 
interfere  with  pregnancy ;  so  that  women  whose  menses  are  habi- 
tually regular  and  natural  are  much  more  likely  to  become  preg- 
nant, after  sexual  intercourse,  than  those  in  whom  the  periods  are 
absent  or  irregular. 

If  pregnancy  happen  to  take  place,  however,  at  any  time  during 
the  child-bearing  period,  the  menses  are  suspended  during  the  con- 
tinuance of  gestation,  and  usually  remain  absent,  after  delivery,  as 
long  as  the  woman  continues  to  nurse  her  child.  They  then  re* 
commence,  and  subsequently  continue  to  appear  as  before. 

The  menstrual  discharge  consists  of  an  abundant  secretion  of 
mucus  mingled  with  blood.  When  the  expected  period  is  about 
to  come  on,  the  female  is  affected  with  a  certain  degree  of  discomfort 
and  lassitude,  a  sense  of  weight  in  the  pelvis,  and  more  or  less  dis- 
inclination to  society.  These  symptoms  are  in  some  instances 
slightly  pronounced,  in  others  more  troublesome.  An  unusual 
discharge  of  vaginal  mucus  then  begins  to  take  place,  which  soon 
becomes  yellowish  or  rusty  brown  in  color,  from  the  admixture  of 
a  certain  proportion  of  blood ;  and  by  the  second  or  third  day  the 
discharge  has  the  appearance  of  nearly  pure  blood.  The  unpleasant 
sensations  which  were  at  first  manifest  then  usually  subside;  and 
the  discharge,  after  continuing  for  a  certain  period,  begins  to  grow 
more  scanty.     Its  color  changes  from  a  pure  red  to  a  brownish  or 


672       OVULATION    AND    FUNCTION    OF    MENSTRUATION. 

rusty  tinge,  until  it  finally  disappears  altogether,  and  tlie  female 
returns  to  her  ordinary  condition. 

The  menstrual  epochs  of  the  human  female  correspond  with  the 
periods  of  cestruation  in  the  lower  animals.  Their  general  resem- 
blance to  these  periods  is  too  evident  to  require  demonstration. 
Like  them,  they  are  absent  in  the  immature  female ;  and  begin 
to  take  place  only  at  the  period  of  puberty,  when  the  aptitude  for 
impregnation  commences.  Like  them,  they  recur  during  the  child- 
bearing  period  at  regular  intervals;  and  are  liable  to  the  same 
interruption  by  pregnancy  and  lactation.  Finally,  their  disappear- 
ance corresponds  with  the  cessation  of  fertility. 

The  periods  of  cestruation,  furthermore,  in  many  of  the  lower 
animals,  are  accompanied,  as  we  have  already  seen,  with  an  unusual 
discharge  from  the  generative  passages ;  and  this  discharge  is  fre- 
quently more  or  less  tinged  with  blood.  In  the  human  female  the 
bloody  discharge  is  more  abundant  than  in  other  instances,  but  it 
is  evidently  a  phenomenon  differing  only  in  degree  from  that  which 
shows  itself  in  many  species  of  animals. 

The  most  complete  evidence,  however,  that  the  period  of  men- 
struation is  in  reality  that  of  ovulation,  is  derived  from  the  results 
of  direct  observation.  A  sufficient  number  of  instances  have  now 
been  observed  to  show  that  at  the  menstrual  epoch  a  Graafian 
vesicle  becomes  enlarged,  ruptures,  and  discharges  its  egg.  Cruik- 
shank'  noticed  such  a  case  so  long  ago  as  1797.  Negrier^  relates 
two  instances,  communicated  to  him  by  Dr.  OUivier  d'Angers,  in 
which,  after  sudden  death  during  menstruation,  a  bloody  and  rup- 
tured Graafian  vesicle  was  found  in  the  ovary.  Bischoff^  speaks  of 
four  similar  cases  in  his  own  observation,  in  three  of  which  the 
vesicle  was  just  ruptured,  and  in  the  fourth  distended,  prominent, 
and  ready  to  burst.  Coste"*  has  met  with  several  of  the  same  kind. 
Dr.  MicheP  found  a  vesicle  ruptured  and  filled  with  blood  in  a 
woman  who  was  executed  for  murder  while  the  mensesr  were  pre- 
sent. We  have  also^  met  with  the  same  appearances  in  a  case  of 
death  from  acute  disease,  on  the  second  day  of  menstruation. 

>  London  Philosophical  Transactions,  1797,  p.  135. 

2  Recherches  sur  les  Ovaires,  Paris,  1840,  p.  78. 

3  Annales  des  Sciences  Naturelles,  August,  1844. 

*  Histoire  du  Developpement  des  Corps  Organises,  Paris,  1847,  vol.  i.  p.  221. 
5  Am.  Journ.  Med.  Sci.,  July,  1848. 

^  Corpus  Luteum  of  Menstruation  and  Pregnancy,  in  Transactions  of  American 
Medical  Association,  Philadelphia,  1851. 


MENSTRUATION,  573 

The  process  of  ovulation,  accordingly,  in  the  human  female, 
accompanies  and  forms  a  part  of  that  of  menstruation.  As  the 
menstrual  period  comes  on,  a  congestion  takes  place  in  nearly  the 
whole  of  the  generative  apparatus ;  in  the  Fallopian  tubes  and  the 
uterus,  as  well  as  in  the  ovaries  and  their  contents.  One  of  the 
Graafian  follicles  is  more  especially  the  seat  of  an  unusual  vascular 
excitement.  It  becomes  distended  by  the  fluid  which  accumulates 
in  its  cavity,  projects  from  the  surface  of  the  ovary,  and  is  finally 
ruptured  in  the  same  manner  as  we  have  already  described  this 
process  taking  place  in  the  lower  animals. 

It  is  not  quite  certain  at  what  particular  period  of  the  menstrual 
flow  the  rupture  of  the  vesicle  and  discharge  of  the  egg  take  place. 
It  is  the  opinion  of  Bischoff,  Pouchet,  and  Eaciborski,  that  the 
regular  time  for  this  rupture  and  discharge  is  not  at  the  commence- 
ment, but  towards  the  termination  of  the  period.  Coste*  has  ascer- 
tained, from  his  observations,  that  the  vesicle  ruptures  sometimes 
in  the  early  part  of  the  menstrual  epoch,  and  sometimes  later.  So 
far  as  we  can  learn,  therefore,  the  precise  period  of  the  discharge 
of  the  egg  is  not  invariable.  Like  the  menses  themselves,  it  may 
apparently  take  place  a  little  earlier,  or  a  little  later,  according  to 
various  accidental  circumstances ;  but  it  always  occurs  at  some 
time  in  connection  with  the  menstrual  flow,,  and  constitutes  the 
most  essential  and  important  part  of  the  catamenial  process. 

The  egg,  when  discharged  from  the  ovary,  enters  the  fimbriated 
extremity  of  the  Fallopian  tube,  and  commences  its  passage  toward 
the  uterus.  The  mechanism  by  which  it  finds  its  way  into  and 
through  the  Fallopian  tube  is  different,  in  the  quadrupeds  and  the 
human  species,  and  in  birds  and  reptiles.  In  the  latter,  the  bulk 
of  the  egg  or  mass  of  eggs  discharged  is  so  great  as  to  fill  entirely 
the  wide  extremity  of  the  oviduct,  and  they  are  afterward  conveyed 
downward  by  the  peristaltic  action  of  the  muscular  coat  of  this 
canal.  In  the  higher  classes,  on  the  contrary,  the  egg  is  micro- 
scopic in  size,  and  would  be  liable  to  be  lost,  were  there  not  some 
further  provision  for  its  safety.  The  wide  extremity  of  the  Fallo- 
pian tube,  accordingly,  which  is  here  directed  toward  the  ovary,  is 
lined  with  ciliated  epithelium ;  and  the  movement  of  the  cilia, 
which  is  directed  from  the  ovary  toward  the  uterus,  produces  a 
kind  of  converging  stream,  or  vortex,  by  which  the  egg  is  neces- 
sarily drawn  toward  the  narrow  portion  of  the  tube,  and  subse- 
quently conducted  to  the  cavity  of  the  uterus. 

'  Loc.  cit. 


574       OVULATION    AND    FUNCTION    OF    MENSTRUATION. 

Accidental  causes,  however,  sometimes  disturb  this  regular  course 
or  passage  of  the  egg.  The  egg  may  be  arrested,  for  example, 
at  the  surface  of  the  ovary,  and  so  fail  to  enter  the  tube  at  all. 
If  fecundated  in  this  situation,  it  will  then  give  rise  to  "  ovarian 
pregnancy."  It  may  escape  from  the  fimbriated  extremity  into  the 
peritoneal  cavity,  and  form  attachments  to  some  one  of  the  neigh- 
boring organs,  causing  "abdominal  pregnancy;"  or  finally,  it  may 
stop  at  any  part  of  the  Fallopian  tube,  and  so  give  origin  to  "  tubal 
pregnancy." 

The  egg,  immediately  upon  its  discharge  from  the  ovary,  is  ready 
for  impregnation.  If  sexual  intercourse  happen  to  take  place  about 
that  time,  the  egg  and  the  spermatic  fluid  meet  in  some  part  of  the 
female  generative  passages,  and  fecundation  is  accomplished.  It 
appears  from  various  observations  of  Bischoff,  Coste,  and  others, 
that  this  contact  may  take  place  between  the  egg  and  the  sperm, 
either  in  the  uterus  or  any  part  of  the  Fallopian  tubes,  or  even 
upon  the  surface  of  the  ovary.  If,  on  the  other  hand,  coitus  do  not 
take  place,  the  egg  passes  down  to  the  uterus  unimpregnated,  loses 
its  vitality  after  a  short  time,  and  is  finally  carried  away  with  the 
uterine  secretions. 

It  is  easily  understood,  therefore,  why  sexual  intercourse  should 
be  more  liable  to  be  followed  by  pregnancy  when  it  occurs  about 
the  menstrual  epoch  than  at  other  times.  This  fact,  which  was  long 
since  established  as  a  matter  of  observation  by  practical  obstetri- 
cians, depends  simply  upon  the  coincidence  in  time  between  men- 
struation and  the  discharge  of  the  egg.  Before  its  discharge,  the 
egg  is  immature,  and  unprepared  for  impregnation ;  and  after  the 
menstrual  period  has  passed,  it  gradually  loses  its  freshness  and 
vitality.  The  exact  length  of  time,  however,  preceding  and  follow- 
ing the  menses,  during  which  impregnation  is  still  possible,  has  not 
been  ascertained.  The  spermatic  fluid,  on  the  one  hand,  retains  its 
vitality  for  an  unknown  period  after  coition,  and  the  egg  for  an 
unknown  period  after  its  discharge.  Both  these  occurrences  may, 
therefore,  either  precede  or  follow  each  other  within  certain  limits, 
and  impregnation  be  still  possible ;  but  the  precise  extent  of  these 
limits  is  still  uncertain,  and  is  probably  more  or  less  variable  in 
different  individuals. 

The  above  facts  indicate  also  the  true  explanation  of  certain 
exceptional  cases,  which  have  sometimes  been  observed,  in  which 
fertility  exists  without  menstruation.  Various  authors  (Churchill, 
Heid,  Velpeau,  &c.)  have  related  instances  of  fruitful  women  in  whom 


MENSTRUATION.  675 

the  menses  were  very  scanty  and  irregular,  or  even  entirely  absent. 
The  menstrual  flow  is,  in  fact,  only  the  external  sign  and  accompa- 
niment of  a  more  important  process  taking  place  within.  It  is 
habitually  scanty  in  some  individuals,  and  abundant  in  others. 
Such  variations  depend  upon  the  condition  of  vascular  activity  of 
the  system  at  large,  or  of  the  uterine  organs  in  particular;  and 
though  the  bloody  discharge  is  usually  an  index  of  the  general 
aptitude  of  these  organs  for  successful  impregnation,  it  is  not  an 
absolute  or  necessary  requisite.  Provided  a  mature  egg  be  dis- 
charged from  the  ovary  at  the  appointed  period,  menstruation  pro- 
perly speaking  exists,  and  pregnancy  is  possible. 

The  blood  which  escapes  during  the  menstrual  flow  is  supplied 
by  the  uterine  mucous  membrane.  If  the  cavity  of  the  uterus  be 
examined  after  death  during  menstruation,  its  internal  surface  is 
seen  to  be  smeared  with  a  thickish  bloody  fluid,  which  may  be 
traced  through  the  uterine  cervix  and  into  the  vagina.  The  Fallo- 
pian tubes  themselves  are  sometimes  found  excessively  congested, 
and  filled  with  a  similar  bloody  discharge.  The  menstrual  blood 
has  also  been  seen  to  exude  from  the  uterine  orifice  in  cases  of  pro- 
cidentia uteri,  as  well  as  in  the  natural  condition  by  examination 
with  the  vaginal  speculum.  It  is  discharged  by  a  kind  of  capillary 
hemorrhage,  similar  to  that  which  takes  place  from  the  lungs  in 
cases  of  haemoptysis,  only  less  sudden  and  violent.  The  blood  does 
not  form  any  visible  coagulum,  owing  to  its  being  gradually  exuded 
from  many  minute  points,  and  mingled  with  a  large  quantity  of 
mucus.  When  poured  out,  however,  more  rapidly  or  in  larger 
quantity  than  usual,  as  in  cases  of  menorrhagia,  the  menstrual  blood 
coagulates  in  the  same  manner  as  if  derived  from  any  other  source. 
The  hemorrhage  which  supplies  it  comes  from  the  whole  extent  of 
the  mucous  membrane  of  the  body  of  the  uterus,  and  is,  at  the  same 
time,  the  consequence  and  the  natural  termination  of  the  periodical 
congestion  of  the  parts. 


576.  MENSTRUATION    AND    PREGNANCY. 


CHAPTER    VI. 

ON   THE   CORPUS   LUTEUM   OF   MENSTEUATION 
AND    PREGNANCY. 

After  the  rupture  of  the  Graafian  follicle  at  the  menstrual 
period,  a  bloody  cavity  is  left  in  the  ovary,  which  is  subsequently 
obliterated  by  a  kind  of  granulating  process,  somewhat  similar  in 
character  to  the  healing  of  an  abscess.  For  the  Graafian  follicle 
is  intended  simply  for  the  formation  and  growth  of  the  egg. 
After  the  egg  therefore  has  arrived  at  maturity  and  has  been  dis- 
charged, the  Graafian  follicle  has  no  longer  any  function  to  per- 
form. It  then  only  remains  for  it  to  pass  through  a  process  of 
obliteration  and  atrophy,  as  an  organ  which  has  become  useless 
and  obsolete.  AYhile  undergoing  this  process,  the  Graafian  follicle 
is  at  one  time  converted  into  a  peculiar,  solid,  globular  body,  which 
is  called  the  cojyus  luteum- ;  a  name  given  to  it  on  account  of  the 
yellow  color  which  it  acquires  at  a  certain  period  of  its  formation. 

We  shall  proceed  to  describe  the  corpus  luteum  in  the  human 
species;  first,  as  it  follows  the  ordinary  course  of  development 
after  menstruation ;  and  secondly,  as  it  is  modified  in  its  growth 
and  appearance  during  the  existence  of  pregnancy. 

I.   CORPUS  LUTEUM  OF  MENSTRUATION. 

"We  have  already  described,  in  the  preceding  chapter,  the  man- 
ner in  which  a  Graafian  follicle,  at  each  menstrual  epoch,  swells, 
protrudes  from  the  surface  of  the  ovary,  and  at  last  ruptures  and 
discharges  its  egg.  At  the  moment  of  rupture,  or  immediately 
after  it,  an  abundant  hemorrhage  takes  place  in  the  human  sub- 
ject from  the  vessels  of  the  follicle,  by  which  its  cavity  is  filled 
with  blood.  This  blood  coagulates  soon  after  its  exudation,  as 
it  would  do  if  extravasated  in  any  other  part  of  the  body,  and 
the  coagulum  is  retained  in  the  interior  of  the  Graafian  follicle. 


CORPUS    LUTEUM    OP    MENSTRUATION.  577 

The  opening  by  which  the  egg  makes  its  escape  is  usually  not  an 

extensive  laceration,  but  a  minute  rounded  perforation,  often  not 

more  than  half  a  line  in  diameter.      A  small  probe,  introduced 

through  this  opening,  passes  directly  into  the 

cavity  of  the  follicle.     If  the  Graafian  follicle  Fig-  1S7. 

be  opened  at  this  time  by  a  longitudinal  inci-  ,. 

sion  (Fig.  187),  it  will  be  seen  to  form  a  globu-  Jfff 

lar   cavity,  one-half  to   three-quarters   of  an  M^T 

inch   in   diameter,  containing   a   soft,   recent, 

dark-colored  coagulum.     This  coagulum  has  ___^^^mmi--- 

no  organic  connection  with  the  walls  of  the 

follicle,  but  lies  loose  in  its  cavity  and  may  be 

easily  turned  out  with  the  handle  of  a  knife.  'w^'"'""^ 

There  is  sometimes  a  slight  mechanical  adhe-  f§| 

sion  of  the  clot  to  the  edges  of  the  lacerated 

opening,   iust  as  the  coagulum  in  a  recently  g«aafiak  folliolb 

c  O'    o  O  J      recently    rnptured    daring 

ligatured  artery  is  entangled  by  the  divided    menstruation,    and    eued 

1  i?j^i*i  1  J  'in  A  1      I      ■with   a    bloody   coagalum ; 

edges  of  the  internal  and  middle  coats ;  but    .^own  m  longitudinal  sec^ 
there  is  no  continuity  of  substance  between    tion.— «.    Tissue    of    the 

,  T    ii  1  1  1  T1         ovary.    6.  Membrane  of  the 

them,  and  the  clot  may  be  everywhere  readily    vesicle,  c.  Point  of  rupture, 
separated  by  careful  manipulation.    The  mem- 
brane of  the  vesicle  presents  at  this  time  a  smooth,  transparent,  and 
vascular  internal  surface,  without  any  alteration  of  color,  consistency, 
or  texture. 

An  important  change,  however,  soon  begins  to  take  place,  both 
in  the  central  coagulum  and  in  the  membrane  of  the  vesicle. 

The  clot,  which  is  at  first  large,  soft,  and  gelatinous,  like  any 
other  mass  of  coagulated  blood,  begins  to  contract ;  and  the  serum 
separates  from  the  coagulum  proper.  The  serum,  as  fast  as  it 
separates  from  the  coagulum,  is  absorbed  by  the  neighboring  parts ; 
and  the  clot,  accordingly,  grows  every  day  smaller  and  denser  than 
before.  At  the  same  time  the  coloring  matter  of  the  blood  under- 
goes the  changes  which  usually  take  place  in  it  after  extravasation, 
and  is  partially  reabsorbed  together  with  the  serum.  This  second 
change  is  somewhat  less  rapid  than  the  former,  but  still  a  diminu- 
tion of  color  is  very  perceptible  in  the  clot,  at  the  expiration  of 
two  weeks. 

The  membrane  of  the  vesicle  during  this  time  is  beginning  to 
undergo  a  process  of  hypertrophy  or  development,  by  which  it 
becomes  thickened  and  convoluted,  and  tends  partially  to  fill  up 
37 


578 


MENSTRUATION    AND    PREGNANCY. 


Fin.  188. 


the  cavity  of  the  follicle.  This  hypertrophy  and  convolution  of 
the  membrane  just  named  commences  and  proceeds  most  rapidly 
at  the  deeper  part  of  the  follicle,  directly  opposite  the  situation  of 
the  superficial  rupture.  From  this  point  the  membrane  gradually 
becomes  thinner  and  less  convoluted  as  it  approaches  the  surface 
of  the  ovary  and  the  edges  of  the  ruptured  orifice. 

At  the  end  of  three  weeks,  this  hypertrophy  of  the  membrane  of 
the  vesicle  has  reached  its  maximum.  The  ruptured  Graafian  fol- 
licle has  now  become  so  completely  solidified  by  the  new  growth 
above  described,  and  by  the  condensation  of  its  clot,  that  it  receives 
the  name  of  the  corpus  luteum.  It  forms  a  perceptible  prominence 
on  the  surface  of  the  ovary,  and  may  be  felt  between  the  fingers 
as  a  well-defined  rounded  tumor,  which  is  nearly  always  somewhat 
flattened  from  side  to  side.     It  measures  about  three-quarters  of  an 

inch  in  length  and  half  an  inch  in 
depth.  On  its  surface  may  be  seen  a 
minute  cicatrix  of  the  peritoneum, 
occupying  the  spot  of  the  original 
rupture. 

On  cutting  it  open  at  this  time  (Fig. 
188),  the  corpus  luteum  is  seen  to  con- 
sist, as  above  described,  of  a  central 
coagulum  and  a  convoluted  wall. 
The  coagulum  is  semi-transparent,  of 
a  gray  or  light  greenish  color,  more 
or  less  mottled  with  red.  The  con- 
voluted wall  is  about  one-eighth  of 
an  inch  thick  at  its  deepest  part,  and 
of  an  indefinite  yellowish  or  rosy 
hue,  not  very  different  in  tinge  from 
the  rest  of  the  ovarian  tissue.  The  convoluted  wall  and  the  con- 
tained clot  lie  simply  in  contact  with  each  other,  as  at  first,  without 
any  intervening  membrane  or  other  organic  connection ;  and  they 
may  still  be  readily  separated  from  each  other  by  the  handle  of  a 
knife  or  the  flattened  end  of  a  probe.  The  corpus  luteum  at  this 
time  may  also  be  stripped  out,  or  enucleated  entire,  from  the  ovarian 
tissue,  just  as  might  have  been  done  with  the  Graafian  follicle  pre- 
viously to  its  rupture.  When  enucleated  in  this  way,  the  corpus 
luteum  presents  itself  under  the  form  of  a  solid  globular  or  flat- 
tened tumor,  with  convolutions  upon  it  somewhat  similar  in  ap- 
pearance to  those  of  the  brain,  and  covered  with  the  remains  of 


OvAitY  cut  open,  sliowiui;  corpus 
luteum  divided  longitudinally;  three 
veek-i  after  menstruation.  From  a  girl 
dead  of  hsemoptysis. 


CORPUS    LUTEUM    OF    MENSTRUATION. 


579 


Fig.  IS 9. 


Ovary,  sKowiiig  corpas 
luteum  four  week^*  after  men- 
struation ;  from  a  woman  dead 
of  apoplexy. 


the  areolar  tissue,  by  which  it  was  previously  connected  with  the 
substance  of  the  ovarj. 

After  the  third  week  from  the  close  of  menstruation,  the  corpus 
luteum  passes  into  a  retrograde  condition.  It  diminishes  percep- 
tibly in  size,  and  the  central  coagulum  con- 
tinues to  be  absorbed  and  loses  still  farther 
its  coloring  matter.  The  whole  body  under- 
goes a  process  of  partial  atrophy;  and  at 
the  end  of  the  fourth  week  it  is  not  more 
than  three-eighths  of  an  inch  in  its  longest 
diameter.  (Fig.  189.)  The  external  cicatrix 
may  still  usually  be  seen,  as  well  as  tlie 
point  where  the  central  coagulum  comes 
in  contact  with  the  peritoneum.  There  is 
still  no  organic  connection  between  the 
central  coagulum  and  the  convoluted  wall  ; 
but  the  partial  condensation  of  the  clot  and 
the  continued  folding  of  the  wall  prevent  the 
separation  of  the  two  being  so  easily  accom- 
plished  as   before,  though  it  may  still   be 

effected  by  careful  management.     The  entire  corpus  luteum  may 
also  still  be  extracted  from  its  bed  in  the  ovarian  tissue. 

The  color  of  the  convoluted  wall,  during  the  early  part  of  this 
retrograde  stage,  instead  of  fading,  like  that  of  the  fibrinous  coagu- 
lum, becomes  more  strongly  marked.  From  having  a  dull  yellowish 
or  rosy  hue,  as  at  first,  it  gradually  as- 
sumes a  brighter  and  more  decided  yellow. 
This  change  of  color  in  the  convoluted 
wall  is  produced  in  consequence  of  a 
kind  of  fatty  degeneration  which  takes 
place  in  its  texture ;  a  large  quantity  of  oil- 
globules  being  deposited  in  it  at  this  time, 
as  may  be  readily  recognized  under  the 
microscope.  At  the  end  of  the  fourth 
week,  this  alteration  in  hue  is  complete; 
and  the  outer  wall  of  the  corpus  luteum 
is  then  of  a  clear  chrome-yellow  color,  by 
which  it  is  readily  distinguished  from  all 
the  neighboring  tissues. 

After  this  period,  the  process  of  atrophy 
and  degeneration  goes  on  rapidly.     The  clot  becomes  constantly 


Fig.  190. 


OvART,  showing  corpiiH  In 
tPuni.  ninn  weeks  after  inennlnia' 
tiiin  ;  from  a  fjirl  dead  of  tuber- 
cular irieniiigitis. 


580  MENSTBUATION   AND    PREGNANCY. 

more  dense  and  shrivelled,  and  is  soon  converted  into  a  minute, 
stellate,  wMte,  or  reddish-wliite  cicatrix.  The  yellow  wall  becomes 
softer  and  more  friable,  as  is  the  case  with  all  tissues  undergoing 
fatty  degeneration,  and  shows  less  distinctly  the  marking  of  its 
convolutions.  At  the  same  time  its  surfaces  become  confounded 
with  the  central  coagulum  on  the  one  hand,  and  with  the  neigh- 
boring tissues  on  the  other,  so  that  it  is  no  longer  possible  to  separate 
them  fairly  from  each  other.  At  the  end  of  eight  or  nine  weeks 
(Fig.  190)  the  whole  body  is  reduced  to  the  condition  of  an  insignifi- 
cant, yellowish,  cicatrix-like  spot,  measuring  less  than  a  quarter  of 
an  inch  in  its  longest  diameter,  in  which  the  original  texture  of  the 
corpus  luteum  can  be  recognized  only  by  the  peculiar  folding  and 
coloring  of  its  constituent  parts.  Subsequently  its  atrophy  goes  on 
in  a  less  active  manner,  and  a  period  of  seven  or  eight  months  some- 
times elapses  before  its  final  and  complete  disappearance. 

The  corpus  luteum,  accordingly,  is  a  formation  which  results 
from  the  filling  up  and  obliteration  of  a  ruptured  Graafian  follicle. 
Under  ordinary  conditions,  a  corpus  luteum  is  produced  at  every 
menstrual  period ;  and  notwithstanding  the  rapidity  with  which  it 
retrogrades  and  becomes  atrophied,  a  new  one  is  always  formed 
before  its  predecessor  has  completely  disappeared. 

"When,  therefore,  we  examine  the  ovaries  of  a  healthy  female,  in 
whom  the  menses  have  recurred  with  regularity  for  some  time 
previous  to  death,  several  corpora  lutea  will  be  met  with,  in  different 
stages  of  formation  and  atrophy.  Thus  we  have  found,  under  such 
circumstances,  four,  five,  six,  and  even  eight  corpora  lutea  in  the 
ovaries  at  the  same  time,  perfectly  distinguishable  by  their  texture, 
but  very  small,  and  most  of  them  evidently  in  a  state  of  advanced 
retrogression.  They  finally  disappear  altogether,  and  the  number 
of  those  present  in  the  ovary,  therefore,  no  longer  corresponds  with 
that  of  the  Graafian  follicles  which  have  been  ruptured. 

II.  CORPUS  LUTEUM  OF  PREGNANCY. 

Since  the  process  above  described  takes  place  at  every  menstrual 
period,  it  is  independent  of  impregnation  and  even  of  sexual  inter- 
course. The  mere  presence  of  a  corpus  luteum,  therefore,  is  no 
indication  that  pregnancy  has  existed,  but  only  that  a  Graafian 
follicle  has  been  ruptured  and  its  contents  discharged.  We  find, 
nevertheless,  that  when  pregnancy  takes  place,  the  appearance  of 
the  corpus  luteum  becomes  so  much  altered  as  to  be  readily  dis- 


CORPUS    LUTEUM    OF    PREGNANCY.  581 

tinguished  from  tliat  which  simply  follows  the  ordinary  menstrual 
process.  It  is  proper,  therefore,  to  speak  of  two  kinds  of  corpora 
lutea ;  one  belonging  to  menstruation,  the  other  to  pregnancy. 

The  difference  between  these  two  kinds  of  corpora  lutea  is  not 
an  essential  or  fundamental  difference ;  since  they  both  originate  in 
the  same  way,  and  are  composed  of  the  same  structures.  It  is, 
properly  speaking,  only  a  difference  in  the  degree  and  rapidity  of 
their  development.  For  while  the  corpus  luteum  of  menstruation 
passes  rapidly  through  its  different  stages,  and  is  very  soon  reduced 
to  a  condition  of  atrophy,  that  of  pregnancy  continues  its  develop- 
ment for  a  long  time,  attains  a  larger  size  and  firmer  organization, 
and  disappears  finally  only  at  a  much  later  period. 

This  variation  in  the  development  and  history  of  the  corpus 
luteum  depends  upon  the  unusually  active  condition  of  the  pregnant 
uterus.  This  organ  exerts  a  powerful  sympathetic  action,  during 
pregnancy,  upon  many  other  parts  of  the  system.  The  stomach 
becomes  irritable,  the  appetite  is  capricious,  and  even  the  mental 
faculties  and  the  moral  disposition  are  frequently  more  or  less 
affected.  The  ovaries,  however,  feel  the  disturbing  influence  of 
gestation  more  certainly  and  decidedly  than  the  other  organs,  since 
they  are  more  closely  connected  with  the  uterus  in  the  ordinary 
performance  of  their  function.  The  moment  that  pregnancy  takes 
place,  the  process  of  menstruation  is  arrested.  No  more  eggs  come 
to  maturity,  and  no  more  Graafian  follicles  are  ruptured,  during  the 
whole  period  of  gestation.  It  is  not  at  all  singular,  therefore,  that 
the  growth  of  the  corpus  luteum  should  also  be  modified,  by  an 
influence  which  affects  so  profoundly  the  system  at  large,  as  well 
as  the  ovaries  in  particular. 

During  the  first  three  weeks  of  its  formation,  the  growth  of  the 
corpus  luteum  is  the  same  in  the  impregnated  as  in  the  unimpreg- 
nated  condition.  After  that  time,  however,  a  difference  becomes 
manifest.  Instead  of  commencing  a  retrograde  course  during  the 
fourth  week,  the  corpus  luteum  of  pregnancy  continues  its  deve- 
lopment. The  external  wall  grows  thicker,  and  its  convolutions 
more  abundant.  Its  color  alters  in  the  same  way  as  previously 
described,  and  becomes  a  bright  yellow  by  the  deposit  of  fatty 
matter  in  microscopic  globules  and  granules. 

By  the  end  of  the  second  month,  the  whole  corpus  luteum  has 
increased  in  size  to  such  an  extent  as  to  measure  seven-eighths  of 
an  inch  in  length  by  half  an  inch  in  depth.  (Fig.  191.)  The  central 
coagulum  has  by  this  time  become  almost  entirely  decolorized,  so  as 


582 


MENSTRUATION    AND    PREGNANCY. 


Cor  PITS    LuTEPM   of  prpsnancy,  at  end  of  second 
mouth  :  from  a  womaa  dead  from  iuduced  abortion. 


to  present  the  appearance  of  a  purely  fibrinous  deposit.  Sometimes 
we  find  tliat  a  part  of  the  serum,  during  its  separation  from  the  clot, 
has  accumulated  in  the  centre  of  the  mass,  as  in  Fig.  191,  forming  a 

little  cavity  containing  a  few 
Fig-  191-  drops  of  clear  fluid  and  in- 

closed by  a  whitish,  fibrinous 
layer,  the  remains  of  the  solid 
portion  of  the  clot.  It  is 
this  fibrinous  layer  which  has 
sometimes  been  mistaken  for 
a  distinct  organized  mem- 
brane, lining  the  internal  sur- 
face of  the  convoluted  wall, 
and  which  has  thus  led  to 
the  belief  that  the  yellow 
matter  of  the  corpus  luteum  is  normally  deposited  outside  the  mem- 
brane of  the  Graafian  follicle.  Such,  however,  is  not  its  real  struc- 
ture. The  convoluted  wall  of  the  corpus  luteum  is  the  membrane 
of  the  follicle  itself,  partially  altered  by  hypertrophy,  as  may  be 
readily  seen  by  examination  in  the  earlier  stages  of  its  growth  ;  and 

the  fibrinous   layer,    situated 
'^^'       '  internally,     is     the     original 

bloody  coagulum,  decolorized 
and  condensed  by  continued 
absorption.  The  existence  of 
a  central  cavity  containing 
serous  fluid,  is  merely  an  oc- 
casional, not  a  constant  pheno- 
menon. More  frequently,  the 
fibrinous  clot  is  solid  through- 
out, the  serum  being  gradually 
absorbed,  as  it  separates  spon- 
taneously from  the  coagulum. 
During  the  third  and  fourth 
months,  the  enlargement  of  the  corpus  luteum  continues ;  so  that  at 
the  end  of  that  time  it  may  measure  seven-eighths  of  an  inch  in 
length  by  three-quarters  of  an  inch  in  depth.  (Fig.  192.)  The  con- 
voluted wall  is  still  thicker  and  more  highly  developed  than  before, 
having  a  thickness,  at  its  deepest  part,  of  three-sixteenths  of  an  inch. 
Its  color,  however,  has  already  begun  to  fade,  and  is  now  of  a  dull 
yellow,  instead  of  the  bright,  clear  tinge  which  it  previously  ex- 


CoRPtrs  LcTEtJM  of  preETiianry,  at  end  of  fourth 
tnoath  ;  from  a  woman  dead  by  poison. 


CORTUS  LUTEUM  OF  PREGNANCY. 


583 


Fi-.  103. 


hibited.  The  central  coagulum,  perfectly  colorless  and  fibrinous 
in  appearance,  is  often  so  mucli  flattened  by  the  lateral  compres- 
sion of  its  mass,  that  it  has  hardly  a  line  in  thickness.  The  other 
relations  of  the  different  parts  of  the  corpus  luteum  remain  the 
same. 

The  corpus  luteum  has  now  attained  its  maximum  of  develop- 
ment, and  remains  without  any  very  perceptible  alteration  during 
the  fifth  and  sixth  months.  It  then  begins  to  retrograde,  diminish- 
ing constantly  in  size  during  the  seventh  and  eighth  months.  Its 
external  wall  fades  still  more  perceptibly  in  color,  becoming  of  a 
faint  yellowish  white,  not  unlike  that  which  it  presented  at  the  end 
of  the  third  week.  Its  texture  is  thick,  soft,  and  elastic,  and  it  is 
still  strongly  convoluted.  An  abundance  of  fine  red  vessels  can  be 
seen  penetrating  from  the  exterior  into  the 
interstices  of  its  convolutions.  The  central 
coagulum  is  reduced  by  this  time  to  the 
condition  of  a  whitish,  radiated  cicatrix. 

The  atrophy  of  the  organ  continues  dur- 
ing the  ninth  month.  At  the  termination  of 
pregnancy,  it  is  reduced  to  the  size  of  half 
an  inch  in  length  and  three-eighths  of  an 
inch  in  depth.  (Fig.  193.)  It  is  then  of  a 
faint  indefinite  hue,  but  little  contrasted 
with  the  remaining  tissues  of  the  ovary. 
The  central  cicatrix  has  become  very  small, 
and  appears  only  as  a  thin  whitish  lamina, 
with  radiating  processes  which  run  in  be- 
tween the  interstices  of  the  convolutions. 
The  whole  mass,  however,  is  still  quite  firm 
and  resisting  to  the  touch,  and  is  readily 
distinguishable,  both  from  its  size  and  tex 

ture,  as  a  prominent  feature  in  the  ovarian  tissue,  and  a  reliable 
indication  of  pregnancy.  The  convoluted  structure  of  its  external 
wall  is  very  perceptible,  and  the  point  of  rupture,  with  its  externa: 
peritoneal  cicatrix,  distinctly  visible. 

After  delivery,  the  corpus  luteum  retrogrades  rapidly.  At  the 
end  of  eight  or  nine  weeks,  it  has  become  so  much  altered  that  its 
color  is  no  longer  distinguishable,  and  only  faint  traces  of  its  con- 
voluted structure  are  to  be  discovered  by  close  examination.  These 
traces  may  remain,  however,  for  a  long  time  afterward,  more  or  less 


Corpus  Lutecji  of  pre^'- 
nancy,  at  term  ;  fiom  a  WDinan 
dead  in  deliver/  from  rupture 
of  the  uterus. 


584  MENSTRUATION    AND   PREGNANCY. 

concealed  in  the  ovarian  tissue.  We  have  distinguished  them  so 
late  as  nine  and  a  half  months  after  delivery.  They  finally  disap- 
pear entirely,  together  with  the  external  cicatrix  which  previously 
marked  their  situation. 

During  the  existence  of  gestation,  the  process  of  menstruation 
being  suspended,  no  new  follicles  are  ruptured,  and  no  new  corpora 
lutea  are  produced ;  and  as  the  old  ones,  formed  before  the  period  of 
conception,  gradually  fade  and  disappear,  the  corpus  luteum  which 
marks  the  occurrence  of  pregnancy  after  a  short  time  exists  alone 
in  the  ovary,  and  is  not  accompanied  by  any  others  of  older  date. 
In  twin  pregnancies,  we  of  course  find  two  corpora  lutea  in  the 
ovaries ;  but  these  are  precisely  similar  to  each  other,  and,  being 
evidently  of  the  same  date,  will  not  give  rise  to  any  confusion. 
Where  there  is  but  a  single  foetus  in  the  uterus,  and  the  ovaries 
contain  two  corpora  lutea  of  similar  appearance,  one  of  them 
belongs  to  an  embryo  which  has  been  blighted  by  some  accident 
in  the  early  part  of  pregnancy.  The  remains  of  the  blighted  em- 
bryo may  often  be  discovered,  in  such  cases,  in  some  part  of  the 
Fallopian  tubes,  where  it  has  been  arrested  in  its  descent  toward 
the  uterus. 

After  the  process  of  lactation  comes  to  an  end,  the  ovaries  again 
resume  their  ordinary  function.  The  Graafian  follicles  mature  and 
rupture  in  succession,  as  before,  and  new  corpora  lutea  follow  each 
other  in  alternate  development  and  disappearance. 

We  find,  then,  that  the  corpus  luteum  of  menstruation  differs  from 
that  of  pregnancy  in  the  extent  of  its  development  and  the  dura- 
tion of  its  existence.  While  the  former  passes  through  all  the  im- 
portant phases  of  its  growth  and  decline  in  the  period  of  two 
months,  the  latter  lasts  from  nine  to  ten  months,  and  presents, 
during  a  great  portion  of  the  time,  a  larger  size  and  a  more  solid 
organization.  It  will  be  observed  that,  even  with  the  corpus 
luteum  of  pregnancy,  the  bright  yellow  color,  which  is  so  import- 
ant a  characteristic,  is  only  temporary  in  its  duration ;  not  making 
its  appearance  till  about  the  end  of  the  fourth  week,  and  again 
disappearing  after  the  sixth  month. 

The  following  table  contains,  in  a  brief  form,  the  characters  of 
the  corpus  luteum,  as  belonging  to  the  two  different  conditions  of 
menstruation  and  pregnancy,  corresponding  with  different  periods 
of  its  development. 


COKPUS  LUTEUM  OF  PREGNANCY. 


585 


At  the  end  of 
three  weeks 
One  month 

Two  months 


Six  months 


CoEPPS  LuTEUM  OF  Menstbuation.      Coep0s  Lutedm  of  Peegnaxcy. 

Three-quarters  of  an  inch  in  diameter ;  central  clot  reddish  ;  con- 
voluted wall  pale. 


Smaller  ;  convoluted  wall  bright 
yellow ;  clot  still  reddish. 

Reduced  to  the  condition  of  an 
insignificant  cicatrix. 


Absent. 


Nine  months    '  Absent. 


Larger;  convoluted  wall  bright 
yellow  ;  clot  still  reddish. 

Seven-eighths  of  an  inch  in  dia- 
meter ;  convoluted  wall  bright 
yellow  ;  clot  perfectly  decolor- 
ized. 

Still  as  large  as  at  end  of  second 
month  ;  clot  fibrinous  ;  convo- 
luted wall  paler. 

One-half  an  inch  in  diameter; 
central  clot  converted  into  a 
radiating  cicatrix ;  the  external 
wall  tolerably  thick  and  convo-- 
luted,  but  without  any  bright 
yellow  color. 


586  DEVELOPMISNT    OF    THE    IMPREGNATED    EGG. 


CHAPTER  VII. 

ON  THE  DEYELOPMENT  OP  THE  IMPREGNATED 
EGG— SEGMENTATION  OF  THE  VITELLUS  — B  L  AS- 
TODERMIC  MEMBRANE— FORMATION  OF  ORGANS 
IN  THE  FROG. 

We  have  seen,  in  the  foregoing  chapters,  how  the  egg,  produced 
in  the  ovarian  follicle,  becomes  gradually  developed  and  ripened, 
until  it  is  ready  to  be  discharged.  The  egg,  accordingly,  passes 
through  several  successive  stages  of  formation,  even  while  still  con- 
tained within  the  ovary ;  and  its  vitellus  becomes  gradually  com- 
pleted, by  the  formation  of  albuminous  material  and  the  deposit  of 
molecular  granulations.  The  last  change  which  the  egg  undergoes, 
in  this  situation,  and  that  which  marks  its  complete  maturity,  is  the 
disappearance  of  the  germinative  vesicle.  This  vesicle,  which  is,  in 
general,  a  prominent  feature  of  the  ovarian  egg,  disappears  but  a 
short  time  previous  to  its  discharge,  or  even  just  at  the  period  of 
its  leaving  the  Graafian  follicle. 

The  egg,  therefore,  consisting  simply  of  the  mature  vitellus  and 
the  vitelline  membrane,  comes  in  contact,  after  leaving  the  ovary, 
and  while  passing  through  the  Fallopian  tube,  with  the  spermatic 
fluid,  and  is  thereby  fecundated.  By  the  influence  of  fecundation, 
a  new  stimulus  is  imparted  to  its  growth ;  and  while  the  vitality 
of  the  unimpregnated  germ,  arrived  at  this  point,  would  have 
reached  its  termination,  the  fecundated  egg,  on  the  contrary, 
starts  upon  a  new  and  more  extensive  course  of  development,  by 
which  it  is  finally  converted  into  the  body  of  the  young  animal. 

The  egg,  in  the  first  place,  as  it  passes  down  the  Fallopian  tube, 
becomes  covered  with  an  albuminous  secretion.  In  the  birds,  as  we 
have  seen,  this  secretion  is  very  abundant,  and  is  deposited  in  suc- 
cessive layers  around  the  vitellus.  In  the  reptiles,  it  is  also  poured 
out  in  considerable  quantity,  and  serves  for  the  nourishment  of  the 
egg  during  its  early  growth.  In  quadrupeds,  the  albuminous  matter 
is  supplied  in  the  same  way,  though  in  smaller  quantity,  by  the 


SEGMENTATION    OF    THE    VITEILUS. 


587' 


Fig.  194. 


mucous  membrane  of  the  Fallopian  tubes,  and  envelopes  the  egg 
in  a  layer  of  nutritious  material. 

A  very  remarkable  change  now  takes  place  in  the  impregnated  egg, 
which  is  known  as  the  spontaneous  division,  or  segmentation,  of  the 
vitellus.  A  furrow  first  shows  itself, 
running  round  the  globular  mass  of  the 
vitellus  in  a  vertical  direction,  which 
gradually  deepens  until  it  has  divided 
the  vitellus  into  two  separate  halves  or 
hemispheres,  (Fig.  194,  a.)  Almost  at 
the  same  time  another  furrow,  run- 
ning at  right  angles  with  the  first, 
penetrates  also  the  substance  of  the 
vitellus  and  cuts  it  in  a  transverse 
direction.  The  vitellus  is  thus  divided 
into  four  equal  portions  (Fig.  194,  b), 
the  edges  and  angles  of  which  are 
rounded  off,  and  which  are  still  con- 
tained in  the  cavity  of  the  vitelline 
membrane.  The  spaces  between 
them  and  the  internal  surface  of  the 
vitelline  membrane  are  occupied  by 
a  transparent  fluid. 

The  process  thus  commenced  goes 
on  by  a  successive  formation  of  fur- 
rows and  sections,  in  various  direc- 
tions. The  four  vitelline  segments 
already  produced  are  thus  subdivided 
into  sixteen,  the  sixteen  into  sixty- 
four,  and  so  on ;  until  the  whole  vi- 
tellus is  converted  into  a  mulberry- 
shaped  mass,  composed  of  minute, 
nearly  spherical  bodies,  which  are 
called  the  "vitelline  spheres."  (Fig. 
194,  c.)  These  vitelline  spheres  have 
a  somewhat  firmer  consistency  than 
the  original  substance  of  the  vitellus ; 
and  this  consistency  appears  to  in- 
crease, as  they  successively  multiply  in  numbers  and  diminish  ia 
size.  At  last  they  have  become  so  abundant  as  to  be  closely 
crowded  together,  compressed  into  polygonal  forms,  and  flattened 


Segmehtation  of   the  Vitellus 


588     DEVELOPMENT  OF  THE  IMPREGNATED  EGG. 

against  the  internal  surface  of  the  vitelline  membrane.  (Fig  194,  d.) 
They  have  bj  this  time  been  converted  into  true  animal  cells ;  and 
these  cells,  adhering  to  each  other  by  their  adjacent  edges,  form  a 
continuous  organized  membrane,  which  is  termed  the  Blastodermic 
membrane. 

During  the  formation  of  this  membrane,  moreover,  the  egg,  while 
passing  through  the  Fallopian  tubes  into  the  uterus,  has  increased 
in  size.  The  albuminous  matter  with  which  it  was  enveloped  has 
liquefied ;  and,  being  absorbed  by  endosmosis  through  the  vitelline 
membrane,  has  furnished  the  materials  for  the  more  solid  and  ex- 
tensive growth  of  the  newly-formed  structures.  It  may  also  be 
seen  that  a  large  quantity  of  this  fluid  has  accumulated  in  the 
central  cavity  of  the  egg,  inclosed  accordingly  by  the  blastodermic 
membrane,  with  the  original  vitelline  membrane  still  forming  an 
external  envelope  round  the  whole. 

The  next  change  which  takes  place  consists  in  the  division  or 
splitting  of  the  blastodermic  membrane  into  two  layers,  which  are 
known  as  the  external  and  internal  layers  of  the  blastodermic  membrane. 
They  are  both  still  composed  exclusively  of  cells ;  but  those  of  the 
external  layer  are  usually  smaller  and  more  compact,  while  those 
of  the  internal  are  rather  larger  and  looser  in  texture.  The  egg 
then  presents  the  appearance  of  a  globular  sac,  the  walls  of  which 
consist  of  three  concentric  layers,  lying  in  contact  with  and  inclos- 
ing each  other,  viz.,  1st,  the  structureless  vitelline  membrane  on  the 
outside ;  2d,  the  external  layer  of  the  blastodermic  membrane,  com- 
posed of  cells ;  and  8d,  the  internal  layer  of  the  blastodermic  mem- 
brane, also  composed  of  cells.  The  cavity  of  the  egg  is  occupied 
by  a  transparent  fluid,  as  above  mentioned. 

This  entire  process  of  the  segmentation  of  the  vitellus  and  the 
formation  of  the  blastodermic  membrane  is  one  of  the  most  re- 
markable and  important  of  all  the  changes  which  take  place  during 
the  development  of  the  egg.  It  is  by  this  process  that  the  simple 
globular  mass  of  the  vitellus,  composed  of  an  albuminous  matter 
and  oily  granules,  is  converted  into  an  organized  structure.  For 
the  blastodermic  membrane,  though  consisting  only  of  cells  nearly 
uniform  in  size  and  shape,  is  nevertheless  a  truly  organized  mem- 
brane, made  up  of  fully  formed  anatomical  elements.  It  is,  more- 
over, the  first  sign  of  distinct  organization  wbich  makes  its  appear- 
ance in  the  egg ;  and  as  soon  as  it  is  completed,  the  body  of  the 
new  foetus  is  formed.  The  blastodermic  membrane  is,  in  fact,  the 
body  of  the  foetus.     It  is  at  this  time,  it  is  true,  exceedingly  simple 


BLASTODERMIC    MEMBRANE.  589 

in  texture ;  but  we  shall  see  hereafter  that  all  the  future  organs 
of  the  body,  however  varied  and  complicated  in  structure,  arise  out 
of  it,  by  modification  and  development  of  its  different  parts. 

The  segmentation  of  the  vitellus,  moreover,  and  the  formation 
of  the  blastodermic  membrane,  take  place  in  essentially  the  same 
manner  in  all  classes  of  animals.  It  is  always  in  this  way  that 
the  egg  commences  its  development,  whether  it  be  destined  to 
form  afterward  a  fish  or  a  reptile,  a  bird,  a  quadruped,  or  a  man. 
The  peculiarities  belonging  to  different  species  show  themselves 
afterward,  by  variations  in  the  manner  and  extent  of  the  develop- 
ment of  different  parts.  In  the  higher  animals  and  in  the  human 
subject  the  development  of  the  egg  becomes  an  exceedingly  com- 
plicated process,  owing  to  the  formation  of  various  accessory 
organs,  which  are  made  requisite  by  the  peculiar  conditions  under 
which  the  development  of  the  embryo  takes  place.  It  is,  in  fact, 
impossible  to  describe  or  understand  properly  the  complex  embry- 
ology of  the  quadrupeds,  and  more  particularly  that  of  the  human 
subject,  without  first  tracing  the  development  of  those  species  in 
which  the  process  is  more  simple.  We  shall  commence  our  descrip- 
tion, therefore,  with  the  development  of  the  egg  of  the  frog,  which 
is  for  many  reasons  particularly  appropriate  for  our  purpose. 

The  egg  of  the  frog,  when  discharged  from  the  body  of  the  female 
and  fecundated  by  the  spermatic  fluid  of  the  male,  is  deposited  in 
the  water,  enveloped  in  a  soft  elastic  cushion  of  albuminous  sub- 
stance. It  is  therefore  in  a  situation  where  it  is  freely  exposed  to 
the  light,  the  air,  and  the  moderate  warmth  of  the  sun's  rays,  and 
where  it  can  absorb  directly  an  abundance  of  moisture  and  appro- 
priate nutritious  material.  We  find  accordingly  that  under  these 
circumstances  the  development  of  the  egg  is  distinguished  by  a 
character  of  great  simplicity;  since  the  whole  of  the  vitellus  is 
directly  converted  into  the  body  of  the  embryo.  There  are  no  acces- 
sory organs  required,  and  consequently  no  complication  of  the 
formative  process. 

The  two  layers  of  the  blastodermic  membrane,  above  described, 
represent  together  the  commencement  of  all  the  organs  of  the  fcBtus. 
They  are  intended,  however,  for  the  production  of  two  different 
systems ;  and  the  entire  process  of  their  development  may  be  ex- 
pressed as  follows :  T/ie  external  layer  of  the  blastodermic  membrane 
produces  the  spinal  column  and  all  the  organs  of  animal  life  ;  while  the 
internal  layer  produces  the  intestinal  canal,  and  all  the  organs  of  vege- 
tative life. 


590     DEVELOPMENT  OF  THE  IMPREGNATED  EGG. 

The  first  sign  of  advancing  organization  in  the  external  layer  of 
the  blastodermic  membrane  shows  itself  in  a  thickening  and  con- 
densation of  its  structure.  This  thiclcened  portion  has  the  form  of  an 
elongated  oval-shaped  spot,  termed  the  "  embryonic  spot"  (Fig.  195), 

the  wide  edges  of  which  are  somewhat 
^ig- 1^5.  more  opatpe  than  the  rest  of  the  blasto- 

dermic membrane.  Inclosed  within 
these  opaque  edges  is  a  narrower  color- 
less and  transparent  space,  the  "area 
pellucida,"  and  in  its  centre  is  a  delicate 
line,  or  furrow,  running  longitudinally 
from  front  to  rear,  which  is  called  the 
"  primitive  trace." 

On  each  side  of  the  primitive  trace, 

Impregnated  Egg,  with  com-  ^'^  ^hc  area  pcllucida,  the  SubstanCC  of 
mencement  of  formation  of  embryo:  the  biustodcrmic  membrane  lisCS  Up  in 
showing  embryouic  spot,  area  pellu-  ,  ,        n  ■, 

cida,  and  primitive  trace.  such  a  manner  as  to  torm  two  nearly 

parallel  vertical  plates  or  ridges,  which 
approach  each  other  over  the  dorsal  aspect  of  the  foetus  and  are 
therefore  called  the  "  dorsal  plates."  They  at  last  meet  on  the 
median  line,  so  as  to  inclose  the  furrow  above  described  and  con- 
vert it  into  a  canal.  This  afterward  becomes  the  spinal  canal,  and 
in  its  cavity  is  formed  the  spinal  cord,  by  a  deposit  of  nervous 
matter  upon  its  internal  surface.  At  the  anterior  extremity  of  this 
canal,  its  cavity  is  large  and  rounded,  to  accommodate  the  brain 
and  medulla  oblongata ;  at  its  posterior  extremity  it  is  narrow  and 
pointed,  and  contains  the  extremity  of  the  spinal  cord. 

In  a  transverse  section  of  the  Qgg  at  this  stage  (Fig.  196),  the 
dorsal  plates  may  be  seen  approaching  each  other  above,  on  each 
side  of  the  primitive  furrow  or  "trace."  At  a  more  advanced 
period  (Fig.  197)  they  may  be  seen  fairly  united  with  each  other, 
so  as  to  inclose  the  cavity  of  the  spinal  canal.  At  the  same  time, 
the  edges  of  the  thickened  portion  of  the  blastodermic  membrane 
grow  outward  and  downward,  so  as  to  spread  out  more  and  more 
over  the  lateral  portions  of  the  vitelline  mass.  These  are  called 
the  "  abdominal  plates ;"  and  as  they  increase  in  extent  they  tend 
to  unite  with  each  other  below  and  inclose  the  abdominal  cavity, 
just  as  the  dorsal  plates  unite  above,  and  inclose  the  spinal  canal. 
At  last  the  abdominal  plates  actually  do  unite  with  each  other  on 
the  median  line  (at  i.  Fig.  197),  embracing  of  course  the  whole 
internal  layer  of  the  blastodermic  membrane  (s),  which  incloses  in 


FORMATION    OF    ORGANS. 


591 


its  turn  the  remains  of  the  original  vitellus  and  the  albuminous 
fluid  which  has  accumulated  in  its  cavity. 


Fig.  193. 


Fig.  197. 


Transverse  section  of  Eg(J  in  an  early 
stage  of  development. — 1.  External  layer 
of  blastodermic  membraae.  2,  2.  Dorsal 
plates.  3.  Internal  layer  of  blastodermic 
membrane. 


Impregnated  Egg,  at  a  somewbat 
more  advanced  period. — 1.  Umbilicus,  or 
point  of  union  between  abdominal  plates. 
2,  2.  Dorsal  plates  united  with  each  other 
on  the  median  line  and  inclosing  the  spinal 
canal.  3,  3.  Abdominal  plates.  4.  Sec- 
tion of  spinal  column,  with  laminae  and 
ribs.  .'5.  Internal  layer  of  blastodermic 
membrane. 


During  this  time,  there  is  formed,  in  the  thickness  of  the  external 
blastodermic  layer,  immediately  beneath  the  spinal  canal,  a  longitu- 
dinal cartilaginous  cord,  called  the  "  chorda  dorsalis."  Around  the 
chorda  dorsalis  are  afterward  developed  the  bodies  of  the  vertebrae 
(Fig.  197,  4),  forming  the  chain  of  the  vertebral  column;  and  the 
oblique  processes  of  the  vertebrae  run  upward  from  this  point  into 
the  dorsal  plates ;  while  the  transverse  processes,  and  ribs,  run  out- 
ward and  downward  in  the  abdominal  plates,  to  encircle  more  or 
less  completely  the  corresponding  portion  of  the  body. 

If  we  now  examine  the  egg  in  longitudinal  section,  while  tins 
process  is  going  on,  the  thickened  portion  of  the  external  blasto- 
dermic layer  may  be  seen  in  profile,  as  at  i,  Fig.  198.  The  anterior 
portion  (2),  which  will  form  the  head,  is  thicker  than  the  posterior 
(3),  which  will  form  the  tail  of  the  young  animal.  As  the  whole 
mass  grows  rapidly,  both  in  the  anterior  and  the  posterior  direc- 
tion, the  head  becomes  very  thick  and  voluminous,  while  the  tail  also 
begins  to  project  backward,  and  the  whole  egg  assumes  a  distinctly 
elongated  form.  (Fig.  199.)    The  abdominal  plates  at  the  same  time 


592 


DEVELOPMENT  OF  THE  IMPREGNATED  EGG. 


meet  upon  its  under  surface,  and  the  point  at  whicii  they  finally 
unite  forms  the  abdominal  cicatrix  or  umbilicus.  The  internal  blas- 
todermic layer  is  seen,  of  course,  in  the  longitudinal  section  of  the 


Fig.  198. 


Diagram  of  Frog's  Egg,  in  an  early 
stage  of  development ;  longitudinal  sec- 
tion.— 1.  Thickened  portion  of  external 
blastodermic  layer,  forming  body  of  fcetus. 
2.  Anterior  extremity  of  foetus  3.  Poste- 
rior extremity.  4.  Internal  layer  of  blas- 
todermic membrane.  5.  Cavity  of  vitellus. 


Fig.  199. 


Egg  of  Fkog,  in  process  of  develop- 
ment. 


egg,  as  well  as  in  the  transverse,  embraced  by  the  abdominal  plates, 
and  inclosing,  as  before,  the  remains  of  the  vitellus. 

As  the  development  of  the  above  parts  goes  on  (Fig.  200),  the 
head  becomes  sill  larger,  and  soon  shows  traces  of  the  formation 

Fig.  200. 


Eaa  OP  Frog,  farther  advanced. 


of  organs  of  special  sense.  The  tail  also  increases  in  size,  and  pro- 
jects farther  from  the  posterior  extremity  of  the  embryo.  The 
spinal  cord  runs  in  a  longitudinal  direction  from  front  to  rear,  and 
its  anterior  extremity  enlarges,  so  as  to  form  the  brain  and  medulla 
oblongata.  In  the  mean  time,  the  internal  blastodermic  layer,  which 
is  subsequently  to  be  converted  into  the  intestinal  canal,  has  been 
shut  in  by  the  abdominal  walls,  and  still  forms  a  perfectly  closed 
sac,  of  a  slightly  elongated  figure,  without  either  inlet  or  outlet. 
Afterward,  the  mouth  is  formed  by  a  process  of  atrophy  and  perfo- 
ration, which  takes  place  through  both  external  and  internal  layers, 


FORMATION    OF    ORGANS.  598 

at  the  anterior  extremity,  wliile  a  similar  perforation,  at  the  poste- 
rior extremity,  results  in  the  formation  of  the  anus. 

All  these  parts,  however,  are  as  yet  imperfect ;  and,  being  merely 
in  the  course  of  formation,  are  incapable  of  performing  any  active 
function. 

By  a  continuation  of  the  same  process,  the  different  portions  of 
the  external  blastodermic  layer  are  further  developed,  so  as  to  re- 
sult in  the  complete  formation  of  the  various  parts  of  the  skeleton, 
the  integument,  the  organs  of  special  sense,  and  the  voluntary 
nerves  and  muscles.  The  tail  at  the  same  time  acquires  sufficient 
size  and  strength  to  be  capable  of  acting  as  an  organ  of  locomo- 
tion. (Fig.  201.)     The  intestinal  canal,  which  has  been  formed  from 

Fig.  201. 


Tadpole  fully  developed. 

the  internal  blastodermic  layer,  is  at  first  a  short,  wide,  and  nearly 
straight  tube,  running  directly  from  the  mouth  to  the  anus.  It 
soon,  however,  begins  to  grow  faster  than  the  abdominal  cavity 
which  incloses  it,  becoming  longer  and  narrower,  and  is  at  the 
same  time  thrown  into  numerous  convolutions.  It  thus  presents 
a  larger  internal  surface  for  the  performance  of  the  digestive 
process. 

Arrived  at  this  period,  the  young  tadpole  ruptures  the  vitelline 
membrane,  by  which  he  has  heretofore  been  inclosed,  and  leaves  the 
cavity  of  the  egg.  He  at  first  fastens  himself  upon  the  remains  of 
the  albuminous  matter  deposited  round  the  egg,  and  feeds  upon  it  for 
a  short  period.  He  soon,  however,  acquires  sufficient  strength  and 
activity  to  swim  about  freely  in  search  of  other  food,  propelling 
himself  by  means  of  his  large,  membranous,  and  muscular  tail. 
The  alimentary  canal  increases  very  rapidly  in  length  and  becomes 
spirally  coiled  up  in  the  abdominal  cavity,  so  as  to  attain  a  length 
from  seven  to  eight  times  greater  than  that  of  the  entire  body. 

After  a  time,  a  change  takes  place  in  the  external  form  of  the 
young  animal.  The  posterior  extremities  or  limbs  begin  to  show 
38 


594 


DEVELOPMENT  OF  THE  IMPREGNATED  EGG. 


themselves,  bj  budding  or  sprouting  from  the  sides  of  the  body, 
just  at  the  base  of  the  tail,  (Fig.  202.)  The  anterior  extremities  also 
grow  at  this  time,  but  are  at  first  concealed  underneath  the  integu- 
ment. They  afterward,  however,  become  liberated,  and  show  them- 
selves externally.  At  first  both  the  fore  and  hind  legs  are  very 
small,  imperfect  in  structure,  and  altogether  useless  for  purposes  of 
locomotioa.  They  soon,  however,  increase  in  size  and  strength; 
and  while  they  keep  pace  with  the  increasing  development  of  the 
whole  body,  the  tail  on  the  contrary  ceases  to  grow,  and  becomes 
shrivelled  and  atrophied.  The  limbs,  in  fact,  are  destined  finally 
to  replace  the  tail  as  organs  of  locomotion;  and  a  time  at  last 
arrives  (Fig.  203)  when  the  tail  has  altogether  disappeared,  while 


Fig.  202. 


Fig.  203. 


Tadpole,  with  limbs  beginning  to  be  formed. 


Perfect  F  k  o  a . 


the  legs  have  become  fully  developed,  muscular  and  powerful. 
Then  the  animal,  which  was  before  confined  to  an  aquatic  mode 
of  life,  becomes  capable  of  living  also  upon  land,  and  a  trans- 
formation is  thus  effected  from  the  tadpole  into  the  perfect  frog. 

During  the  same  time,  other  changes  of  an  equally  important 
character  have  taken  place  in  the  internal  organs.  The  tadpole  at 
first  breathes  by  gills;  but  these  organs  subsequently  become 
atrophied  and  disappear,  being  finally  replaced  by  well  developed 
lungs.  The  structure  of  the  mouth,  also,  of  the  integument,  and 
of  the  circulatory  system,  is  altered  to  correspond  with  the  varying 
conditions  and  wants  of  the  growing  animal ;  and  all  these  changes 
taking  place  in  part  successively  and  in  part  simultaneously, 
bring  the  animal  at  last  to  a  state  of  complete  formation. 


FORMATION    OF    ORGANS   IN    THE    FROG.  595 

The  process  of  development  may  then  be  briefly  recapitulated  as 
follows : — 

1.  The  blastodermic  membrane,  produced  by  the  segmentation 
of  the  vitellus,  consists  of  two  cellular  layers,  viz.,  an  external  and 
an  internal  blastodermic  layer. 

2.  The  external  layer  of  the  blastodermic  membrane  incloses  by 
its  dorsal  plates  the  cerebro-spinal  canal,  and  by  its  abdominal 
plates  the  abdominal  or  visceral  cavity. 

8.  The  internal  layer  of  the  blastodermic  membrane  forms  the 
intestinal  canal,  which  becomes  lengthened  and  convoluted,  and 
communicates  with  the  e^vterior  by  a  mouth  and  anus  of  secondary 
formation. 

4.  Finally  the  cerebro-spinal  axis  and  its  nerves,  the  skeleton 
the  organs  of  special  sense,  the  integument,  and  the  muscles,  aro 
developed  from  the  external  blastodermic  layer ;  while  the  anterior 
and  posterior  extremities  are  formed  from  the  same  layer  by  a  pro- 
cess of  sprouting,  or  continuous  growth. 


596 


THE    UMBILICAL    VESICLE. 


CHAPTER   VIII. 


THE   UMBILICAL  YESICLE. 


Fig.  204. 


In  the  frog,  as  we  have  seen,  the  abdominal  plates,  closing 
together  in  front  and  underneath  the  body  of  the  animal,  shut  in 
directly  the  whole  of  the  vitellus,  and  join  each  other  upon  the 
median  line,  at  the  umbilicus.  The  whole  remains  of  the  vitellus 
are  then  inclosed  in  the  abdomen  of  the  animal,  and  in  the  intestinal 
sac  formed  by  the  internal  blastodermic  layer. 

In  many  instances,  however,  as,  for  example,  in  several  kinds  of 
fish,  and  in  all  the  birds  and  quadrupeds,  the  abdominal  plates  do 

not  immediately  embrace  the  whole  of 
the  vitelline  mass,  but  tend  to  close 
together  about  its  middle;  so  that  the 
vitellus  is  constricted,  in  this  way,  and 
divided  into  two  portions:  one  internal, 
and  one  external.  (Fig.  204.)  As  the 
process  of  development  proceeds,  the  body 
of  the  foetus  increases  in  size,  out  of  pro- 
portion to  the  vitelline  sac,  and  the  con- 
striction just  mentioned  becomes  at  the 
same  time  more  strongly  marked ;  so  that 
the  separation  between  the  internal  and  external  portions  of  the 
vitelline  sac  is  nearly  complete.  (Fig.  205.)  The  internal  layer  of 
the  blastodermic  membrane  is  by  the  same  means  divided  into 
two  portions,  one  of  which  forms  the  intestinal  canal,  while  the 
other,  remaining  outside,  forms  a  sac-like  appendage  to  the  abdo- 
men, which  is  known  by  the  name  of  the  umhilical  vesicle. 

The  umbilical  vesicle  is  accordingly  lined  by  a  portion  of  the 
internal  blastodermic  layer,  continuous  with  the  mucous  membrane 
of  the  intestinal  canal ;  while  it  is  covered  on  the  outside  by  a  por- 
tion of  the  external  blastodermic  layer,  continuous  with  the  integu- 
ment of  the  abdomen. 


Eggof  Fish,  showing  forma- 
tion of  umbilical  vesicle. 


THE    UMBILICAL    VESICLE.  597 

After  the  young  animal  leaves  the  egg,  the  umbilical  vesicle 
in  some  species  becomes  withered  and  atrophied  by  the  absorption 
of  its  contents;    while  in  others,  the  abdominal  walls  gradually 

Fig.  205. 


Young  Fish  with  umbilical  vesicle. 

extend  over  it,  and  crowd  it  back  into  the  abdomen ;  the  nutritious 
matter  which  it  contained  passing  from  the  cavity  of  the  vesicle 
into  that  of  the  intestine  by  the  narrow  passage  or  canal  which 
remains  open  between  them. 

In  the  human  subject,  however,  as  well  as  in  the  quadrupeds,  the 
umbilical  vesicle  becomes  more  completely  separated  from  the  abdo- 
men than  in  the  cases  just  mentioned.  There  is  at  first  a  wide  com- 
munication between  the  cavity  of  the  umbilical  vesicle  and  that  of 
the  intestine;  and  this  communication,  as  in  other  instances,  becomes 
gradually  narrowed  by  the  increasing  constriction  of  the  abdominal 
walls.  Here,  however,  the  constriction  proceeds  so  far  that  the 
opposite  surfaces  of  the  canal  come  in  contact  with  each  other,  and 
adhere ;  so  that  the  narrow  passage  previously 
existing,  between  the  cavity  of  the  intestine  Fig.  206. 

and  that  of  the  umbilical  vesicle,  is  obliterated, 
and   the  vesicle  is   then   connected  with  the 
abdomen  only  by  an  impervious  cord.     This 
cord   afterward  elongates,  and   becomes  con- 
verted into  a  slender,  thread-like  pedicle  (Fig. 
206),  passing  out  from   the  abdomen  of  the 
foetus,  and  connected  by  its  farther  extremity 
with  the  umbilical  vesicle,  which  is  filled  with 
a  transparent,  colorless  fluid.     The  umbilical     „  "^.^J^rcre^^^ule 
"vesicle  is  very  distinctly  visible  in  the  human     fifth  week, 
fcetus  so  late  as  the  end  of  the  third  month. 
After  that  period  it  diminishes  in  size,  and  is  gradually  lost  in  the 
advancing  development  of  the  neighboring  parts. 

In  the  formation  of  the  umbilical  vesicle,  we  have  the  first  varia- 


598  THE    UMBILICAL    VESICLE. 

tion  from  the  simple  plan  of  development  described  in  the  preceding 
chapter.  Here,  the  whole  of  the  vitellus  is  not  directly  converted 
into  the  body  of  the  embryo ;  but  while  a  part  of  it  is  taken,  as 
usual,  into  the  abdominal  cavity,  and  used  immediately  for  the 
purposes  of  nutrition,  a  part  is  left  outside  the  abdomen,  in  the 
umbilical  vesicle,  a  kind  of  secondary  organ  or  appendage  of  the 
foetus.  The  contents  of  the  umbilical  vesicle,  however,  are  after- 
ward absorbed,  and  so  appropriated,  finally,  to  the  nourishment  of 
the  newly-formed  tissues. 


AMNION    AND    ALLANTOIS.  599 


CHAPTER   IX. 

AMNION  AND  ALL  ANTOIS,  — DE  V  ELO  PM  ENT  OF 
THE  CHICK. 

We  shall  now  proceed  to  the  description  of  two  other  accessory 
organs,  which  are  formed,  during  the  development  of  the  fecundated 
egg,  in  all  the  higher  classes  of  animals.  These  are  the  amnion  and 
the  allantois  ;  two  organs  which  are  always  found  in  company  with 
each  other,  since  the  object  of  the  first  is  to  provide  for  the  forma- 
tion of  the  second.  The  amnion  is  formed  from  the  external  layer 
of  the  blastodermic  membrane,  the  allantois  from  the  internal  layer. 

In  the  frog  and  in  fish,  as  we  have  seen,  the  egg  is  abundantly 
supplied  with  moisture,  air,  and  nourishment,  by  the  water  with 
which  it  is  surrounded.  It  can  absorb  directly  all  the  gaseous  and 
liquid  substances,  which  it  requires  for  the  purposes  of  nutrition 
and  growth.  The  absorption  of  oxygen,  the  exhalation  of  carbonic 
acid,  and  the  imbibition  of  albuminous  and  other  liquids,  can  all 
take  place  without  difficulty  through  the  simple  membranes  of  the 
egg;  particularly  as  the  time  required  for  the  formation  of  the 
embryo  is  very  short,  and  as  a  great  part  of  the  process  of  develop- 
ment remains  to  be  accomplished  after  the  young  animal  leaves 
the  egg. 

But  in  birds  and  quadrupeds,  the  time  required  for  the  develop- 
ment of  the  foetus  is  longer.  The  young  animal  also  acquires  a 
much  more  perfect  organization  during  the  time  that  it  remains 
inclosed  within  the  egg ;  and  the  processes  of  absorption  and  exha- 
lation necessary  for  its  growth,  being  increased  in  activity  to  a 
corresponding  degree,  require  a  special  organ  for  their  accomplish- 
ment. This  special  organ,  destined  to  bring  the  blood  of  the  foetus 
into  relation  with  the  atmosphere  and  external  sources  of  nutrition, 
is  the  allantois. 

In  the  frog  and  the  fish,  the  internal  blastodermic  layer,  forming 
the  intestinal  mucous  membrane,  is  inclosed  everywhere,  as  above 
described,  by  the  external   layer,  forming  the  integument;    and 


600  AMNION    AND    ALLANTOIS. 

consequently  it  can  nowhere  come  in  contact  with  the  investing 
membrane  of  the  egg.  But  in  the  higher  animals,  the  internal 
blastodermic  layer,  which  is  the  seat  of  the  greatest  vascularity, 
and  which  is  destined  to  produce  the  allantois,  is  made  to  come  in 
contact  with  the  external  membrane  of  the  egg  for  purposes  of 
exhalation  and  absorption ;  and  this  can  only  be  accomplished  by 
opening  a  passage  for  it  through  the  external  germinative  layer. 
This  is  done  in  the  following  manner,  by  the  formation  of  the 
amjiion. 

Soon  after  the  body  of  the  foetus  has  begun  to  be  formed  by  the 
thickening  of  the  external  layer  of  the  blastodermic  membrane, 
a  double  fold  of  this  external  layer  rises  up  on  all  sides  about 
the  edges  of  the  newly-formed  embryo ;  so  that  the  body  of  the 
foetus  appears  as  if  sunk  in  a  kind  of  depression,  and  surrounded 
with  a  membranous  ridge  or  embankment,  as  in 
Fig.  207.  'Pig.  207.     The  embryo  (c)  is  here  seen  in  profile, 

with  the  double  membranous  folds,  above  men- 
tioned, rising  up  just  in  advance  of  the  head, 
and  behind  the  posterior  extremity.     It  must  be 
understood,  of  course,  that  the  same  thing  takes 
place  on  the  two  sides  of  the  foetus,  by  the  forma- 
Diagram  of  fkcun-    tiou   of  lateral   folds   simultaneously   with    the 
formatL^o?LmnioTi    appcaraucc  of  thosc  in  front  and  behind.     As  it 
ti.  viteiius.  6.  External    ig  thcsc  folds  which  are  destined   to  form   the 

layer    of    blastodermic  .  ,,  n     t   jt        //  •    j  •      i'  i  i     m 

membrane,  c.  Body  of    amniou,  they  are  called  the  "amniotic  folds." 

embryo.  d,d.  Amniotic        ^hc  amuiotic  folds  coutinuc  to  grow,  and  ex- 
folds,    e.  Vitelline  mem-  _.  .  „  .,.  .  .,, 

trane.  tend  themscIves,  lorward,  backward,  and  laterally, 

until  they  approach  each  other  at  a  point  over 
the  back  of  the  foetus  (Fig.  208),  which  is  termed  the  "  amniotic 
umbilicus."  Their  opposite  edges  afterward  actually  come  in  con- 
tact with  each  other  at  this  point,  and  adhere  together,  so  as  to 
shut  in  a  space  or  cavity  (Fig.  208,  b)  between  their  inner  surface 
and  the  body  of  the  foetus.  This  space,  which  is  filled  with  a  clear 
fluid,  is  called  the  amniotic  cavity.  At  the  same  time,  the  intestinal 
canal  has  begun  to  be  formed,  and  the  umbilical  vesicle  has  been 
partially  separated  from  it,  by  the  constriction  of  the  abdominal 
walls  on  the  under  surface  of  the  body. 

There  now  appears  a  prolongation  or  diverticulum  (Fig.  208,  c) 
growing  out  from  the  posterior  portion  of  the  intestinal  canal,  and 
following  the  course  of  the  amniotic  fold  which  has  preceded  it; 
occupying,  as  it  gradually  enlarges  and  protrudes,  the  space  left 


AMNION    AND    ALLANTOIS, 


601 


FECaNDATED  EgO. 

farther  advanced. — a. 
Umbilical  vesicle,  h. 
Amniotic  cavity,  c.  Al- 
lantoic. 


Fig.  209. 


vacant  by  tlie  rising  up  of  the  amniotic  fold.     This  diverticulum 
is  the  commencement  of  the  allantois.     It  is  an  elongated  mem- 
branous sac,  continuous  with  the  posterior  portion  of  the  intestine, 
and  containing  bloodvessels  derived  from  those 
of  the  intestinal  circulation.     The  cavity  of  the 
allantois  is  also  continuous  with  the  cavity  of 
the  intestine. 

After  the  amniotic  folds  have  approached  and 
touched  each  other,  as  already  described,  over 
the  back  of  the  foetus,  at  the  amniotic  umbilicus, 
the  adjacent  surfaces,  thus  brought  in  contact, 
fuse  together,  so  that  the  cavities  of  the  two 
folds,  coming  respectively  from  front  and  rear, 
are  separated  only  by  a  single  membranous  par- 
tition (Fig.  209,  c)  running  from  the  inner  to  the 
outer  lamina  of  the  amniotic  folds.     This  parti- 
tion itself  soon  after  atrophies  and  disappears ;  and  the  inner  and 
outer  laminae  become  consequently  separated  from  each  other.    The 
inner  lamina  (Fig.  209,  a)  which  remains  con- 
tinuous with  the  integument  of  the  foetus,  in- 
closing the  body  of  the  embryo  in  a  distinct 
cavity,  is  called  the  amnion  (Fig.  210,  h),  and 
its  cavity  is  known  as  the  amniotic  cavity. 
The  outer  lamina  of  the  amniotic  fold,  on  the 
other  hand  (Fig,  209,  h),  recedes  farther  and 
farther  from  the  inner,  until  it  comes  in  con- 
tact with  the  original  vitelline  membrane,  still 
covering  the  exterior  of  the  egg ;  and  by  con- 
tinued growth  and  expansion  it  at  last  fuses 
with  the  vitelline  membrane  and  unites  with 
its  substance,  so  that  the  two  membranes  form 
but  one.   This  membrane,  formed  by  the  fusion 
and  consolidation  of  two  others,  constitutes  then 
the  external  investing  membrane  of  the  Qgg. 
The  allantois,  during  all  this  time,  is  increas- 
ing in  size  and  vascularity.     Following  the  course  of  the  amniotic 
folds  as  before,  it  insinuates  itself  between  them,  and  of  course  soon 
comes  in  contact  with  the  external  investing  membrane  just  de- 
scribed.    It  then  begins  to  expand  laterally  in  every  direction, 
enveloping  more  and  more  the  body  of  the  foetus,  and  bringing  its 
vessels  into  contact  with  the  external  membrane  of  the  egg. 


Fecundated  Egs, 
with  allantoLs  nearly  com- 
plete.— a.  Inner  lamina  of 
amniotic  fold.  h.  Outer  la- 
mina of  ditto,  c.  Point 
where  the  amniotic  foWs 
come  in  contact.  The  allan- 
tois is  seen  penetrating  be- 
tween the  inner  and  outer 
laminaj  of  the  amniotic 
folds. 


602  AMNION    AND   ALLANTOIS. 

By  a  continuation  of  tlie  above  process,  the  allantois  at  last 
grows  to  such  an  extent  as  to  envelope  completely  the  body  of  the 
embryo,  together  with  the  amnion ;  its  two 
Fig.  210.  extremities  coming  in  contact  with  each 

other  and  fusing  together  over  the  back  of 
the  foetus,  just  as  the  amniotic  folds  had 
previously  done.  (Fig.  210.)  It  ]ines,  there- 
fore, the  whole  internal  surface  of  the  in- 
vesting membrane  with  a  flattened,  vascu- 
lar sac,  the  vessels  of  which  come  from  the 
interior  of  the  body  of  the  foetus,  and  which 
Fecundated^  Ego,    with     Still  communicatcs  wlth  the  cavity  of  the 

allantois  fully  formed. -«.    Urn-       intCStinal  Caual. 

bilical  vesicle,    b.    Amuion.     c.  ^     .  .  -  „  ,  -  .      . 

Allantois.  It  IS  cvidcut,  irom  the  above  description, 

that  there  is  a  close  connection  between  the 
formation  of  the  amnion  and  that  of  the  allantois.  For  it  is  only 
in  this  manner  that  the  allantois,  which  is  an  extension  of  the  in- 
ternal layer  of  the  blastodermic  membrane,  can  come  to  be  situated 
outside  the  foetus .  and  the  amnion,  and  be  brought  into  relation 
with  external  surrounding  media.  The  two  laminae  of  the  amni- 
otic folds,  in  fact,  by  separating  from  each  other  as  above  described, 
open  a  passage  for  the  allantois,  and  allow  it  to  come  in  contact 
with  the  external  membrane  of  the  egg. 

In  order  to  explain  more  fully  the  physiological  action  of  the 
allantois,  we  shall  now  proceed  to  describe  the  process  of  develop- 
ment, as  it  takes  place  in  the  egg  of  the  fowl. 

In  order  that  the  embryo  may  be  properly  developed  in  any 
case,  it  is  essential  that  it  be  freely  supplied  with  air,  warmth, 
moisture,  and  nourishment.  The  egg  of  the  fowl  contains  alread}, 
when  discharged  from  the  generative  passages,  a  sufficient  quantity 
of  moisture  and  albuminous  material.  The  necessary  warmth  is 
supplied  by  the  body  of  the  parent  during  incubation ;  while  the 
atmospheric  gases  can  pass  and  repass  through  the  porous  egg- 
shell, and  by  endosmosis  through  the  fibrous  membranes  which 
line  its  cavity. 

When  the  egg  is  first  laid,  the  vitellus,  or  yolk,  is  enveloped  in 
a  thick  layer  of  semi-solid  albumen.  On  the  commencement  of 
incubation,  a  liquefaction  takes  place  in  the  albumen  immediately 
above  that  part  of  the  vitellus  which  is  occupied  by  the  cicatri- 
•cula ;  so  that  the  vitellus  rises  or  floats  upward  toward  the  surface, 
by  virtue  of  its  spe^iiiic  gravity,  and  the  cicatricula  comes  to  be 


DEVELOPMENT    OF    THE    CHICK, 


603 


placed  almost  immediately  underneath  the  lining  membrane  of  the 
egg-shell.  As  the  cicatricula  is  the  spot  from  which  the  process  of 
embryonic  development  commences,  the  body  of  the  young  foetus 
is  by  this  arrangement  placed  in  the  most  favorable  position  for 
the  reception  of  warmth  and  other  necessary  external  influences 
through  the  egg-shell.  The  liquefied  albumen  is  also  absorbed  by 
the  vitelline  membrane,  and  the  vitellus  thus  becomes  larger,  softer, 
and  more  diffluent  than  before  the  commencement  of  incubation. 

As  soon  as  the  circulatory  apparatus  of  the  embryo  has  been 
fairly  formed,  two  minute  arteries  are  seen  to  run  out  from  its 
lateral  edges  and  spread  into  the  neighboring  parts  of  the  blasto- 
dermic membrane,  breaking  up  into  inosculating  branches,  and 
covering  the  adjacent  portions  of  the  vitellus  with  a  plexus  of 
capillary  bloodvessels.  The  space  occupied  in  the  blastodermic 
membrane,  on  the  surface  of  the  vitellus,  by  these  vessels,  is  called 
the  area  vasculosa.    (Fig.  211.)    It  is  of  a  nearly  circular  shape, 

Fig.  211. 


EoG  OF  Fowl  during  early  periods  of  incubation  ;  showing  the  body  of  the  embryo,  and  the 
area  vasculosa  partially  covering  the  surface  of  the  vitellus. 


and  is  limited,  on  its  outer  edge,  by  a  terminal  vein  or  sinus,  called 
the  "  sinus  terminalis."  The  blood  is  returned  to  the  body  of  the 
fo3tus  by  two  veins  which  penetrate  beneath  its  edges,  one  near  the 
head  and  one  near  the  tail. 

The  area  vasculosa  tends  to  increase  in  extent,  as  the  develop- 
ment of  the  foitus  proceeds  and  its  circulation  becomes  more  active. 
It  soon  covers  the  upper  half,  or  hemisphere,  of  the  vitellus,  and 
the  terminal  sinus  then  runs  like  an  equator  round  the  middle  of 
the  vitelline  sphere.     As  the  growth  of  the  vascular  plexus  con- 


604 


AMNION"    AND    ALLANTOIS. 


tinues,  it  passes  this  point,  and  embraces  more  and  more  of  the  in- 
ferior, as  well  as  of  the  superior  hemisphere,  the  vessels  converging 
toward  its  under  surface,  until  at  last  nearly  the  whole  of  the 
vitellus  is  covered  with  a  network  of  inosculating  capillaries. 

The  function  of  the  vessels  of  the  area  vasculosa  is  to  absorb 
nourishment  from  the  cavity  of  the  vitelline  sac.  As  the  albumen 
liquefies  during  the  process  of  incubation,  it  passes  by  endosmosis, 
more  and  more  abundantly,  into  the  vitelline  cavity ;  the  whole 
vitellus  growing  constantly  larger  and  more  fluid  in  consistency. 
The  blood  of  the  foetus,  then  circulating  in  the  vessels  of  the  area 
vasculosa,  absorbs  freely  the  oleagino-albuminous  matters  of  the 
vitellus,  and,  carrying  them  back  to  the  foetus  by  the  returning 
veins,  supplies  the  newly-formed  tissues  and  organs  with  abun- 
dance of  appropriate  nourishment. 

During  this  period  the  amnion  and  the  allantois  have  been  also 
in  process  of  formation.  At  first  the  body  of  the  foetus  lies  upon 
its  abdomen,  as  in  the  cases  previously  described ;  but,  as  it  increases 
in  size,  it  alters  its  position  so  as  to  lie  more  upon  its  side.  The 
allantois  then,  emerging  from  the  posterior  portion  of  the  abdominal 
cavity,  turns  directly  upward  over  the  body  of  the  foetus,  and  comes 
immediately  in  contact  with  the  shell  membrane.    (Fig.  212.)     It 

Fig.  212. 


Eaa  OF  Fowl  at  a  more  advanced  period  of  development.  The  body  of  the  fcctus  is  enveloped 
by  the  amnion,  and  has  the  umbilical  vesicle  hanging  from  its  under  surface;  while  the  vascular 
allantois  is  seen  turning  upward  and  spreading  out  over  the  internal  surface  of  the  shell-membrane. 


then  spreads  out   rapidly,  extending  toward  the  extremities  and 
down  the  sides  of  the  egg,  enveloping  more,  and  more  completely 


DEVELOPMENT    OF    THE    CHICK.  605 

the  foetus  and  the  vitelline  sac,  and  taking  the  place  of  the  albumen 
which  has  been  liquefied  and  absorbed. 

It  will  also  be  seen,  bj  reference  to  the  figure,  that  the  umbilical 
vesicle  is  at  the  same  time  formed  bj  the  separation  of  part  of  the 
vitellus  from  the  abdomen  of  the  chick ;  and  the  vessels  of  the  area 
vasculosa,  which  were  at  first  distributed  over  the  vitellus,  now 
ramify,  of  course,  upon  the  surface  of  the  umbilical  vesicle. 

At  last  the  allantois,  by  its  continued  growth,  envelopes  nearly 
the  whole  of  the  remaining  contents  of  the  egg ;  so  that  toward  the 
later  periods  of  incubation,  at  whatever  point  we  break  open  the 
egg,  we  find  the  internal  surface  of  the  shell-membrane  lined  with 
a  vascular  membranous  expansion,  supplied  by  arteries  which 
emerge  from  the  abdomen  of  the  foetus. 

It  is  easy  to  see,  accordingly,  with  what  readiness  the  absorption 
and  exhalation  of  gases  may  take  place  by  means  of  the  allantois. 
The  air  penetrates  from  the  exterior  through  the  minute  pores  of 
the  calcareous  shell,  and  then  acts  upon  the  blood  in  the  vessels  of 
the  allantois  very  much  in  the  same  manner  that  the  air  in  the  minute 
bronchial  tubes  and  air- vesicles  of  the  lungs  acts  upon  the  blood  in 
the  pulmonary  capillaries.  Examination  of  the  egg,  furthermore, 
at  various  periods  of  incubation,  shows  that  changes  take  place  in 
it  which  are  entirely  analogous  to  those  of  respiration. 

The  egg,  in  the  first  place,  during  its  development,  loses  water  by 
exhalation.  This  exhalation  is  not  a  simple  effect  of  evaporation, 
but  is  the  result  of  the  nutritive  changes  going  on  in  the  interior 
of  the  egg ;  since  it  does  not  take  place,  except  in  a  comparatively 
slight  degree,  in  unimpregnated  eggs,  or  in  those  which  are  not 
incubated,  though  they  may  be  freely  exposed  to  the  air.  The 
exhalation  of  fluid  is  also  essential  to  the  processes  of  development, 
for  it  has  often  been  found,  in  hatching  eggs  by  artificial  warmth, 
that  if  the  air  of  the  chamber  in  which  they  are  inclosed  become 
unduly  charged  with  moisture,  so  as  to  retard  or  prevent  further 
exlialation,  the  eggs  readily  become  spoiled,  and  the  development 
of  the  embryo  is  arrested.  The  loss  of  weight  during  natural  incu- 
bation, principally  due  to  the  exhalation  of  water,  has  been  found 
by  Baudrimont  and  St.  Ange'  to  be  over  15  per  cent,  of  the  entire 
weight  of  the  egg. 

Secondly,  the  egg  absorbs  oxygen  and  exhales  carbonic  acid. 
The  two  observers  mentioned  above,  ascertained  that  during  eigh* 

•  Du  DSveloppement  da  Foetus.     Paris,  IS.*)©,  p.  143. 


606  AMNION    AND    ALLANTOIS. 

teen  days'  incubation,  the  egg  absorbs  nearly  2  per  cent,  of  its 
weight  of  oxygen,  while  the  quantity  of  carbonic  acid  exhaled  from 
the  sixteenth  to  the  nineteenth  day  of  incubation  amounts  to  no  less 
than  3  grains  in  the  twenty -four  hours.^  It  is  curious  to  observe, 
also,  that  in  the  egg  during  incubation,  as  well  as  in  the  adult 
animal,  more  oxygen  is  absorbed  than  is  returned  by  exhalation 
under  the  form  of  carbonic  acid. 

It  is  evident,  therefore,  that  a  true  respiration  takes  place,  by 
means  of  the  allantois,  through  the  membranes  of  the  shell. 

The  allantois,  however,  is  not  simply  an  organ  of  respiration ;  it 
takes  part  also  in  the  absorption  of  nutritious  matter.  As  the  pro- 
cess of  development  advances,  the  skeleton  of  the  young  chick,  at 
first  entirely  cartilaginous,  begins  to  ossify.  The  calcareous  mat- 
ter, necessary  for  this  ossification,  is,  in  all  probability,  derived  from 
the  shell.  The  shell  is  certainly  lighter  and  more  fragile  toward 
the  end  of  incubation  than  at  first ;  and,  at  the  same  time,  the  cal- 
careous ingredients  of  the  bones  increase  in  quantity.  The  lime- 
salts,  requisite  for  the  process  of  ossification,  are  apparently  ab- 
sorbed from  the  shell  by  the  vessels  of  the  allantois,  and  by  them 
transferred  to  the  skeleton  of  the  growing  chick ;  so  that,  in  the 
same  proportion  that  the  former  becomes  weaker,  the  latter  grows 
stronger.  This  diminution  in  density  of  the  shell  is  connected  not 
only  with  the  development  of  the  skeleton,  but  also  with  the  final 
escape  of  the  chick  from  the  egg.  This  deliverance  is  accomplished 
mostly  by  the  movements  of  the  chick  itself,  which  become,  at  a 
certain  period,  sufficiently  vigorous  to  break  out  an  opening  in  the 
attenuated  and  weakened  egg-shell.  The  first  fracture  is  generally 
accomplished  by  a  stroke  from  the  end  of  the  bill ;  and  it  is  pre- 
cisely at  this  point  that  the  solidification  of  the  skeleton  is  most 
advanced.  The  egg-shell  itself,  therefore,  which  at  first  only  serves 
for  the  protection  of  the  imperfectly-formed  embryo,  afterward 
furnishes  the  materials  which  are  used  to  accomplish  its  own  demo- 
lition, and  at  the  same  time  to  efifect  the  escape  of  the  fully  deve- 
loped foetus. 

Toward  the  latter  periods  of  incubation,  the  allantois  becomes 
more  and  more  adherent  to  the  internal  surface  of  the  shell-mem- 
brane. At  last,  when  the  chick,  arrived  at  the  full  period  of  de- 
velopment, escapes  from  its  confinement,  the  allantoic  vessels  ate 
torn  off  at  the  umbilicus ;  and  the  allantois  itself,  cast  off  as  a  use- 

»  Op.  cit.,  pp.  138  and  149. 


DEVELOPMENT    OF    THE    CHICK.  607 

less  and  effete  organ,  is  left  behind  in  the  cavity  of  the  abandoned 
egg-shell.  The  allantois  is,  therefore,  strictly  speaking,  a  fcetal 
organ.  Developed  as  an  accessory  structure  from  a  portion  of  the 
intestinal  canal,  it  is  exceedingly  active  and  important  during  the 
middle  and  latter  periods  of  incubation;  but  when  the  chick  is 
completely  formed,  and  has  become  capable  of  carrying  on  an  in- 
dependent existence,  both  the  amnion  and  the  allantois  are  detached 
and  thrown  off  as  obsolete  structures,  their  place  being  afterward 
supplied  by  other  Organs  belonging  to  the  adult  condition. 


608      DEVELOPMENT    OF   THE    EGG   IN    HUMAN    SPECIES. 


CHAPTEK   X. 

DEVELOPMENT    OF    THE   EGG   IN    THE    HUMAN 
SPECIES.— FORMATION  OF  THE  CHORION. 


"We  have  already  described,  in  a  preceding  chapter,  the  manner 
in  which  the  outer  lamina  of  the  amniotic  fold  becomes  adherent 
to  the  adjacent  surface  of  the  vitelline  membrane,  so  as  to  form 
with  it  but  a  single  layer ;  and  in  which  these  two  membranes,  thus 
fused  and  united  with  each  other,  form  at  that  time  the  single  ex- 
ternal investing  membrane  of  the  egg.  The  allantois,  in  its  turn, 
afterward  comes  in  contact  with  the  investing  membrane,  and  lies 
immediately  beneath  it,  as  a  double  vascular  membranous  sac.  In 
the  egg  of  the  human  subject  the  development  of  the  membranes, 
though  carried  on  essentially  upon  the  same  plan  with  that  which 
we  have  already  described,  undergoes,  in  addition,  some  further 
modifications,  which  we  shall  now  proceed  to  explain. 

The  first  of  these  peculiarities  is  that  the  allantois,  after  spread- 
ing out  upon  the  inner  surface  of 
•^"  the  external  investing  membrane, 

adheres  to,  and  fuses  with  it,  just 
as  the  outer  lamina  of  the  amni- 
otic fold  has  previously  fused 
with  the  vitelline  membrane.  At 
the  same  time,  the  two  layers  be- 
longing to  the  allantois  itself  also 
come  in  contact  and  fuse  toge- 
ther; so  that  the  cavity  of  the 
allantois  is  obliterated,  and  instead 
of  forming  a  membranous  sac  con- 
taining fluid,  this  organ  is  convert- 
ed into  a  simple  vascular  membrane. 
(Fig.  213.)  This  membrane, 
moreover,  being,  after  a  time,  thoroughly  fused  and  united  with  the 
two  which  have  preceded  it,  takes  the  place  which  was  previously 


Hitman  Ovum,  about  the  end  of  the  first 
month  ;  showing  formation  of  chorion. — 1. 
Umbilical  vesicle.    2.  Amnion.    3.  Chorion. 


FORMATION    OF    THE    CHORION".  609 

occupied  by  them.  It  is  then  termed  the  chorion,  and  thus  becomes 
the  sole  external  investing  membrane  of  the  egg. 

We  find,  therefore,  that  the  chorion,  that  is,  the  external  coat  or 
investment  of  the  egg,  is  formed  successively  by  three  distinct 
membranes,  as  follows:  first,  the  original  vitelline  membrane; 
secondly,  the  outer  lamina  of  the  amniotic  fold ;  and,  thirdly,  the 
allantois ;  the  last  predominating  over  the  two  former  by  the  rapidity 
of  its  growth,  and  absorbing  them  into  its  substance,  so  that  they 
become  finally  completely  incorporated  with  its  texture. 

It  is  easy  to  see,  also,  how,  in  consequence  of  the  above  process, 
the  body  of  the  foetus,  in  the  human  egg,  becomes  inclosed  in  two 
distinct  membranes,  viz.,  the  amnion,  which  is  internal  and  conti- 
nuous with  the  foetal  integument,  and  the  chorion,  which  is  external 
and  supplied  with  vessels  from  the  cavity  of  the  abdomen.  The 
umbilical  vesicle  is,  of  course,  situated  between  the  two ;  and  the 
rest  of  the  space  between  the  chorion  and  the  amnion  is  occupied 
by  a  semi-fluid  gelatinous  material,  somewhat  similar  in  appearance 
to  that  of  the  vitreous  body  of  the  eye. 

The  obliteration  of  the  cavity  of  the  allantois  takes  place  very 
early  in  the  human  subject,  and,  in  fact,  keeps  pace  almost  entirely 
with  the  progress  of  its  growth ;  so  that  this  organ  never  presents, 
in  the  human  egg,  the  appearance  of  a  hollow  sac,  filled  with 
fluid,  but  rather  that  of  a  flattened  vascular  membrane,  enveloping 
the  body  of  the  foetus,  and  forming  the  external  membrane  of  the 
egg.  Notwithstanding  this  difference,  however,  the  chorion  of  the 
human  subject,  in  respect  to  its  mode  of  formation,  is  the  same 
thing  with  the  allantois  of  the  lower  animals ;  its  chief  peculiarity 
consisting  in  the  fact  that  its  opposite  surfaces  are  adherent  to  each 
other,  instead  of  remaining  separate  and  inclosing  a  cavity  filled 
with  fluid. 

The  next  peculiarity  of  the  human  chorion  is,  that  it  becomes 
shaggy.  Even  while  the  egg  is  still  very  small,  and  has  but  recently 
found  its  way  into  the  uterine  cavity,  its  exterior  is  already  seen 
to  be  covered  with  little  transparent  prominences,  like  so  many 
villi  (Fig.  213),  which  increase  the  extent  of  its  surface,  and  assist 
in  the  absorption  of  fluids  from  without.  The  villi  are  at  this  time 
quite  simple  in  form,  and  altogether  homogeneous  in  structure. 

As  the  egg  increases  in  size,  the  villi  rapidly  elongate,  and  be- 
come divided  and  ramified  by  the  repeated  budding  and  sprouting 
of  lateral  offshoots  from  every  part.  After  this  process  of  growth 
89 


610      DEVELOPMENT    OF    THE    EGG    IN    HUMAN    SPECIES. 


Fig.  214. 


has  gone  on  for  some  time,  the  external  surface  of  the  chorion  pre- 
sents a  uniformly  velvety  or  shaggy  appearance,  owing  to  its  being 
covered  everywhere  with  these  tufted  and  compound  villosities. 

The  villosities  themselves,  when  examined  by  the  microscope, 
have  an  exceedingly  well-marked  and  characteristic  appearance. 
(Fio-.  214.)     They  originate  from  the  surface  of  the  chorion  by  a 

somewhat  narrow  stem,  and  divide 
into  a  multitude  of  secondary  and 
tertiary  branches,  of  varying  size 
and  figure ;  some  of  them  slender 
and  filamentous,  others  club-shaped, 
many  of  them  irregularly  swollen  at 
various  points.  All  of  them  termi- 
nate by  rounded  extremities,  giving 
to  the  whole  tuft  a  certain  resem- 
blance to  some  varieties  of  sea-weed. 
The  larger  trunks  and  branches  of 
the  villosity  are  seen  to  contain  nu- 
merous minute  nuclei,  imbedded  in 
a  nearly  homogeneous,  or  finely  gra- 
nular substratum.  The  smaller  ones 
appear,  under  a  low  magnifying 
power,  simply  granular  in  texture. 

These  villi  are  altogether  peculiar 
in  appearance,  and  quite  unlike  any 
other  structure  which  may  be  met  with  in  the  body.  Whenever  we 
find,  in  the  uterus,  any  portion  of  a  membrane  having  villosities 
like  these,  we  may  be  sure  that  pregnancy  has  existed ;  for  such 
villosities  can  only  belong  to  the  chorion,  and  the  chorion  itself  is 
%  part  of  the  foetus.  It  is  developed,  as  we  have  seen,  as  an  out- 
growth from  the  intestinal  canal,  and  can  only  exist,  accordingly, 
as  a  portion  of  the  fecundated  egg.  The  presence  of  portions  of  a 
shaggy  chorion  is  therefore  as  satisfactory  proof  of  the  existence 
of  pregnancy,  as  if  he  had  found  the  body  of  the  fcetus  itself. 

While  the  villosities  which  we  have  just  described  are  in  pro- 
cess of  formation,  the  allantois  itself  has  completed  its  growth,  and 
has  become  converted  into  a  permanent  chorion.  The  bloodvessels 
coming  from  the  allantoic  arteries  accordingly  ramify  over  the 
chorion,  and  supply  it  with  a  tolerably  abundant  vascular  network. 
The  growth  of  the  fcetus,  moreover,  at  this  time,  has  reached  such 
a  state  of  activity,  that  it  requires  to  be  supplied  with  nourishment 


Compound  villosity  of  HuMAy  Cho- 
rion, ramified  extremity.  From  a  three 
months'  foetus.     Magnified  30  diameters. 


FORMATION    OF    THE    CHORION. 


611 


Fig.  215. 


Extrem'ty  of  villositt  o? 
Chorion,  more  highly  maga:- 
fied;  showiug  the  arrangement  cf 
bloodvessels  in  its  interior. 


by  vascular  absorption,  instead  of  the  slow  process  of  imbibition, 
wbich  has  heretofore  taken  place  through  the  comparatively  incom- 
plete and  structureless  villi  of  the  cho- 
rion. The  capillary  vessels,  accordingly, 
with  which  the  chorion  is  supplied,  begin 
to  penetrate  into  the  substance  of  its  vil- 
losities.  They  enter  the  base  or  stem  of 
each  villosity,  and,  following  every  divi- 
sion of  its  compound  ramifications,  finally 
reach  its  rounded  extremities.  Here  they 
turn  upon  themselves  in  loops  (Fig.  215), 
like  the  vessels  in  the  papillae  of  the  skin, 
and  retrace  their  course,  to  unite  finally 
with  the  venous  trunks  of  the  chorion. 

The  villi  of  the  chorion  are,  therefore, 
very  analogous  in  structure  to  those  of 
the  intestine;  and  their  power  of  absorp- 
tion, as  in  other  similar  instances,  corre- 
sponds with  the  abundance  of  their  ramifications,  and  the  extent 
of  their  vascularity. 

It  must  be  remembered,  also,  that  these  vessels  all  come  from  the 
abdomen  of  the  foetus ;  and  that  whatever  substances  are  taken  up 
by  them  are  transported  directly  to  the  interior  of  the  embryo,  and 
used  for  the  nourishment  of  its  tissues.  The  chorion,  therefore,  as 
soon  as  its  villi  and  bloodvessels  are  completely  developed,  becomes 
an  exceedingly  active  organ  in  the  nutrition  of  the  foetus ;  and  con- 
stitutes, in  fact,  the  only  means  by  which  new  material  can  be  in- 
troduced from  without. 

The  existence  of  this  general  vascularity  of  the  chorion  affords 
also,  as  Coste  was  the  first  to  point  out,  a  striking  indication  that 
this  membrane  is  in  reality  identical  with  the  allantois  of  the 
lower  animals.  If  the  reader  will  turn  back  to  the  illustrations  of 
the  formation  of  the  amnion  and  allantois  (Chap.  IX.),  he  will  see 
that  the  first  chorion  or  investing  membrane  is  formed  exclusively 
by  the  vitelline  membrane,  which  is  never  vascular  and  cannot  be- 
come so  by  itself,  since  it  has  no  direct  connection  with  the  foetus. 
The  second  chorion  is  formed  by  the  union  of  the  vitelline  mem- 
brane with  the  outer  lamina  of  the  amniotic  fold.  Both  laminae 
of  the  amniotic  fold  are  at  first  vascular,  since  they  are  portions  of 
the  external  blastodermic  layer,  and  derive  their  vessels  fVom  the 
integument  of  the  foitus.     But  after  the  outer  lamina  has  become 


612      DEVELOPMENT    OF    THE    EGG   IN    HUMAN   SPECIES. 


completely  separated  from  tlie  inner,  by  the  disappearance  of  the 
partition  which  for  a  time  connected  the  two  with  each  other  (Fig. 
209,  c),  this  source  of  vascular  supply  is  cut  off;  and  the  second 
chorion  cannot,  therefore,  remain  vascular  after  that  period.  But 
the  third  or  permanent  chorion,  that  is,  the  allantois,  derives  its  ves- 
sels directlv  from  those  of  the  foetus,  and  retains  its  connection  with 
them  during  the  whole  period  of  gestation.  A  chorion,  therefore^ 
which  is  universally  and  permanently  vascular,  can  be  no  other 
than  the  allantois,  converted  into  an  external  investing  membrane 
of  the  egg. 

Thirdly,  the  chorion,  which  is  at  one  time,  as  we  have  seen,  every- 
where villous  and  shaggy,  becomes  afterward  partially  bald.  This 
change  begins  to  take  place  about  the  end  of  the  second  month. 
It  commences  at  a  point  opposite  the  situation  of  the  foetus  and  the 
insertion  of  the  foetal  vessels.  The  villosities  of  this  region  cease 
growing ;  and  as  the  entire  egg  continues  to  enlarge,  the  villosities 
at  the  point  indicated  fail  to  keep  pace  with  its  growth,  and  with 
the  progressive  expansion  of  the  chorion.  They  accordingly  be- 
come at  this  part  thinner  and  more  scattered,  leaving  the  surface 
of  the  chorion  comparatively  smooth  and  bald.  This  baldness  in- 
creases in  extent  and  becomes  more  and  more  complete,  spreading 

and  advancing  over  the  adja- 
^'g-  2^^*  cent  portions  of  the  chorion, 

until  at  least  two-thirds  of  its 
surface  have  become  nearly 
or  quite  destitute  of  villosities. 
At  the  opposite  point  of  the 
surface  of  the  egg,  however, 
that  portion,  namely,  which 
corresponds  with  the  insertion 
of  the  foetal  vessels,  the  villosi- 
ties, instead  of  becoming  atro- 
phied, continue  to  grow;  and 
this  portion  of  the  chorion  be- 
comes even  more  shaggy  and 
thickly  set  than  before.  The 
consequence  is  that  the  chorion  afterward  presents  a  very  different 
appearance  at  different  portions  of  its  surface.  (Fig.  216.)  The 
greater  part  of  it  is  smooth;  but  a  certain  portion,  constituting 
about  one-third  of  the  whole,  is  covered  with  a  soft  and  spongy 
mass  of  long,  thickly-set,  compound  villosities.     It  is  this  thickened 


Human  Ovum  at  end  of  third  month  ;  showing 
placental  portion  of  the  chorion  fully  formed. 


FORMATION    OF    THE    CHORION.  613 

and  shaggy  portion,  which  is  afterward  concerned  in  the  formation 
of  the  placenta  ;  while  the  remaining  smooth  portion  continues  to 
be  known  under  the  name  of  the  chorion.  The  placental  portion 
of  the  chorion  becomes  distinctly  limited  and  separated  from  the 
remainder  by  about  the  end  of  the  third  month. 

The  vascularity  of  the  chorion  keeps  pace,  in  its  different  parts 
respectively,  with  the  atrophy  and  development  of  its  villosities. 
As  the  villosities  shrivel  and  disappear  over  a  part  of  its  extent, 
the  looped  capillary  vessels,  which  they  at  first  contained,  disappear 
also ;  so  that  the  smooth  portion  of  the  chorion  shows  afterward 
only  a  few  straggling  vessels  running  over  its  surface,  and  does  not 
contain  any  abundant  capillary  plexus.  In  the  thickened  portion, 
on  the  other  hand,  the  vessels  lengthen  and  ramify  to  an  extent 
corresponding  with  that  of  the  villosities  in  which  they  are  situated. 
The  allantoic  arteries,  coming  from  the  abdomen  of  the  foetus,  enter 
the  villi,  and  penetrate  through  their  whole  extent ;  forming,  at  the 
placental  portion  of  the  chorion,  a  mass  of  tufted  and  ramified  vas- 
cular loops,  while  over  the  rest  of  the  membrane  they  are  merely 
distributed  as  a  few  single  and  scattered  vessels. 

The  chorion,  accordingly,  is  the  external  investing  membrane  of 
the  egg,  produced  by  the  consolidation  and  transformation  of  the 
allantois.  The  placenta,  furthermore,  so  far  as  it  has  now  been 
described,  is  evidently  a  part  of  the  chorion;  that  part,  namely 
which  is  thickened,  shaggy,  and  vascular,  while  the  remainder  is 
comparatively  thin,  smooth,  and  membranous. 


614      DEVELOPMENT   OF    UTERINE   MUCOUS   MEMBRANE. 


CHAPTER   XI. 

DEVELOPMENT  OP  UTERINE  MUCOUS   MEMBRANE.— 
FORMATION    OF   THE    DEOIDUA. 

In  fish,  reptiles,  and  birds,  the  egg  is  either  provided  with  a  sup- 
ply of  nutritious  material  contained  within  its  membranes,  or  it  is 
so  placed,  after  its  discharge  from  the  body  of  the  parent,  that  it 
can  absorb  these  materials  from  without.  Thus,  in  the  egg  of  the 
bird,  the  young  embryo  is  supported  upon  the  albuminous  matter 
deposited  around  the  vitellus ;  while  in  the  frog  and  fish,  moisture, 
oxygen,  saline  substances,  &;c.,  are  freely  imbibed  from  the  water 
in  which  the  egg  is  placed. 

But  in  the  quadrupeds,  as  well  as  in  the  human  species,  the  egg 
is  of  minute  size,  and  the  quantity  of  nutritious  matter  which  it 
contains  is  sufficient  to  last  only  for  a  very  short  time.  Moreover, 
the  development  of  the  foetus  takes  place  altogether  within  the  body 
of  the  female,  and  no  supply,  therefore,  can  be  obtained  directly 
from  the  external  media.  In  these  instances,  accordingly,  the  mu- 
cous membrane  of  the  uterus,  which  is  found  to  be  unusually 
developed  and  increased  in  functional  activity  during  the  period  of 
gestation,  becomes,  a  source  of  nutrition  for  the  fecundated  egg. 
The  uterine  mucous  membrane,  thus  developed  and  hypertrophied, 
is  known  by  the  name  of  the  Decidua. 

It  has  received  this  name  because,  as  we  shall  hereafter  see,  it 
becomes  exfoliated  and  thrown  off,  at  the  same  time  that  the  egg 
itself  is  finally  discharged. 

The  mucous  membrane  of  the  body  of  the  uterus,  in  the  unimpreg- 
nated  condition,  is  quite  thin  and  delicate,  and  presents  a  smooth 
and  slightly  vascular  internal  surface.  There  is,  moreover,  no  layer 
of  submucous  cellular  tissue  between  it  and  the  muscular  substance 
of  the  uterus;  so  that  the  mucous  membrane  cannot  here,  ^s  in 
most  other  organs,  be  easily  dissected  up  and  separated  from  the 
subjacent  parts.  The  structure  of  the  mucous  membrane  itself, 
however,  is  sufficiently  well  marked  and  readily  distinguishable 


FORMATION    OF    THK    DECIDUA. 


615 


Fig.  217. 


Uterine  Mucors  Membkane,  as 
seen  in  vertical  section. — a.  Free  surface, 
6.  Attached  surface. 


from   that   of  other   parts.      It   consists,   throughout,    of  minute 
tubular  follicles,  ranged  side  bj  side,  and  running  perpendicularly 
to  the  free  surface  of  the  mucous  membrane.   (Fig.  217.)     Near 
this    free    surface,   they    are    nearly 
straight;  but  toward  the  deeper  sur- 
face of  the  mucous  membrane,  where 
they  terminate  in  blind  extremities, 
they  become  more  or  less  wavy  or 
spiral  in  their  course.     The  tubules 
are  about  yi^  of  an  inch  in  diameter, 
and   are   lined   throughout  with   co- 
lumnar epithelium.  (Fig,  218.)    They 
occupy  the  entire  thickness  of  the  ute- 
rine mucous  membrane,  their  closed 
extremities  resting  upon  the  subjacent 

muscular  tissue,  while  their  mouths  open  into  the  cavity  of  the  ute- 
rus.   A  few  fine  bloodvessels  penetrate  the  mucous  membrane  from 
below,  and,  running  upward 
between  the  tubules,  encircle  ^^" 

their  superficial  extremities 
with  a  capillary  network. 
There  is  no  areolar  tissue  in 
the  uterine  mucous  mem- 
brane, but  only  a  small  quan- 
tity of  spindle-shaped  fibro- 
plastic fibres,  scattered  be- 
tween the  tubules. 

As  the  fecundated  egg  is 
about  to  descend  into  the 
cavity  of  the  uterus,  the  mu- 
cous membrane,  above  de- 
scribed, takes  on  an  increas- 
ed activity  of  growth  and 
an  unusual  development.  It 
becomes  tumefied  and  vascular ;  and,  as  it  increases  in  thickness,  it 
projects,  in  rounded  eminences  or  convolutious,  into  the  uterine 
cavity,  (Fig.  219.)  In  this  process,  the  tubules  of  the  uterus  in- 
crease in  length,  and  also  become  wider ;  so  that  their  open  mouths 
may  be  readily  seen  by  the  naked  eye  upon  the  uterine  surface,  as 
numerous  minute  perforations.  The  bloodvessels  of  the  mucous 
membrane  also  enlarge  and  multiply,  and  inosculate  freely  with 


Uterine    Tubctles,  from   mucous  membrane  or 
uuimpregnated  human  uterus. 


616      DEVELOPMENT    OF    UTERINE    MUCOUS    MEMBRANE. 

each  other ;  so  that  the  vascular  network  encircling  the  tubules  be- 
comes more  extensive  and  abundant. 

The  internal  surface  of  the  uterus,  accordingly,  after  this  process 
has  been  for  some  time  going  on,  presents  a  thick,  rich,  soft,  vas- 
cular, and  velvety  lining,  quite  different  from  that  which  is  to  be 
found  in  the  unimpregnated  condition.  In  consequence  of  this 
difference,  the  lining  membrane  of  the  uterus,  in  the  impregnated 
condition,  was  formerly  supposed  to  be  an  entirely  new  product, 
thrown  out  by  exudation  from  the  uterine  surface,  and  analogous, 
in  this  respect,  to  the  inflammatory  exudations  of  croup  and  pleu- 
risy. It  is  now  known,  however,  to  be  no  other  than  the  mucous 
membrane  of  the  uterus  itself,  thickened  and  hypertrophied  to  an 
extraordinary  degree,  but  still  retaining  all  its  natural  connections 
and  its  original  anatomical  structure. 

The  hypertrophied  mucous  membrane,  above  described,  consti- 
tutes the  Decidua  vera.  Its  formation  is  confined  altogether  to  the 
body  of  the  uterus,  the  mucous  membrane  of  the  cervix  taking  no 
part  in  the  process,  but  retaining  its  original  appearance.  The 
decidua  vera,  therefore,  commences  above,  at  the  orifices  of  the 
Fallopian  tubes,  and  ceases  below,  at  the  situation  of  the  os  inter- 
num. The  cavity  of  the  cervix,  meanwhile,  begins  to  be  filled 
with  an  abundant  secretion  of  its  peculiarly  viscid  mucus,  which 
blocks  up,  more  or  less  completely,  its  passage,  and  protects  the 
internal  cavity.  But  there  is  no  membranous  partition  at  this  time 
covering  the  os  internum,  and  the  mucous  membranes  of  the  cervix 
and  of  the  body  of  the  uterus,  though  very  different  in  appearance, 
are  still  perfectly  continuous  with  each  other.  When  we  cut  open 
the  cavity  of  the  uterus,  therefore,  in  this  condition,  we  find  its 
internal  surface  lined  with  the  decidua  vera,  with  the  opening  of 
the  OS  internum  below  and  the  orifices  of  the  Fallopian  tubes  above, 
perfectly  distinct,  and  in  their  natural  positions.  (Fig.  219.) 

As  the  fecundated  egg,  in  its  journey  from  above  downward, 
passes  the  lower  orifice  of  the  Fallopian  tube,  it  insinuates  itself 
between  the  opposite  surfaces  of  the  uterine  mucous  membrane, 
and  becomes  soon  afterward  lodged  in  one  of  the  furrows  or  de- 
pressions between  the  projecting  convolutions  of  the  decidua. 
(Fig.  219.)  It  is  at  this  situation  that  an  adhesion  subsequently 
takes  place  between  the  external  membranes  of  the  egg,  on  the 
one  hand,  and  the  uterine  decidua  on  the  other.  Now,  at  the  point 
where  the  egg  becomes  fixed  and  entangled,  as  above  stated,  a  still 
more  rapid  development  than  before  takes  place  in  the  uterine 


FORMATION    OF   THE    DECIDUA. 


617 


iriucous  membrane.  Its  projecting  folds  begin  to  grow  up  around 
the  egg  in  such  a  manner  as  to  partially  inclose  it  in  a  kind  of 
circumvallation  of  the  decidua,  and  to  shut  it  off,  more  or  less  com- 


Fig.  219. 


Fig.  220. 


IvPREONiiTED  Uterus;  showinsr 
formation  of  decidua.  The  decidua  is 
represented  in  black ;  and  the  egg  is 
seen,  at  the  fundus  of  the  uterus,  en- 
gaged between  two  of  its  projecting 
convolutions. 


iMPREauATED  Uterits,  With  pro- 
jecting folds  of  decidua  growing  up 
around  the  egg.  The  narrow  opening 
where  the  edges  of  the  folds  approach 
each  other,  is  seen  over  the  most  promi- 
nent portion  of  the  egg. 


FiV.  221. 


pletely,  from  the  general  cavity  of  the  uterus.  (Fig.  220.)     The  egg 
is  thus  soon  contained  in  a  special  cavity  of  its  own,  which  still 
communicates  for  a  time  with  the  general  cavity  of  the  uterus  by 
a  small  opening,  situated  over  its  most 
prominent  portion,  which  is  known  as  the 
"  decidual  umbilicus."    As  the  above  pro- 
cess of  growth  goes  on,  this  opening  be- 
comes narrower  and  narrower,  while  the 
projecting  folds  of  decidua  approach  each 
other  over  the  surface  of  the  egg.    At 
last  these  folds  actually  touch  each  other 
and   unite,   forming   a   kind   of  cicatrix 
which  remains  for  a  certain  time,  to  mark 
the  situation  of  the  original  opening. 

When  the  development  of  the  uterus  and 
its  contents  has  reached  this  point  (Fig. 
221),  it  will  be  seen  that  the  egg  is  com- 
pletely inclosed  in  a  distinct  cavity  of  its 

own ;  being  everywhere  covered  with  a  decidual  layer  of  new  for- 
mation, which  has  thus  gradually  enveloped  it,  and  by  which  it  is 
concealed  from  view  when  the  uterine  cavity  is  laid  open.     This 


I  M  P  R  E  <1  N  A  T  li  1>       U  T  K  K  r  S  ;  — 

showing  egg  completely  inclosed 
by  deoidaa  reflexa. 


618      DEVELOPMENT    OF    UTERINE    MUCOUS    MEMBRANE. 

newly-formed  layer  of  decidua,  enveloping,  as  above  described,  the 
projecting  portion  of  the  egg,  is  called  the  Decidua  reflexa  ;  because 
it  is  reflected  over  the  egg,  by  a  continuous  growth  from  the  general 
surface  of  the  uteri  ne  mucous  membrane.  The  orifices  of  the  uterine 
tubules,  accordingly,  in  consequence  of  the  manner  in  which  the 
decidua  reflexa  is  formed,  will  be  seen  not  only  on  its  external  sur- 
face, or  that  which  looks  toward  the  cavity  of  the  uterus,  but  also  on 
its  internal  surface,  or  that  which  looks  towaf  d  the  egg.    , 

The  decidua  vera,  therefore,  is  the  original  mucous  membrane 
lining  the  surface  of  the  uterus  ;  while  the  decidua  reflexa  is  a  new- 
formation,  which  has  grown  up  round  the  egg  and  inclosed  it  in  a 
distinct  cavity. 

If  abortion  occur  at  this  time,  the  mucous  membrane  of  the 
uterus,  that  is,  the  decidua  vera,  is  thrown  off,  and  of  course  brings 
away  with  it  the  egg  and  decidua  reflexa.  On  examining  the  mass 
discharged  in  such  an  abortion,  the  egg  will  accordingly  be  found 
imbedded  in  the  substance  of  the  decidual  membrane.  One  side 
of  this  membrane,  where  it  has  been  torn  away  from  its  attachment 
to  the  uterine  walls,  is  ragged  and  shaggy ;  the  other  side,  corres- 
ponding to  the  cavity  of  the  uterus,  is  smooth  or  gently  convoluted, 
and  presents  very  distinctly  the  orifices  of  the  uterine  tubules; 
while  the  egg  itself  can  only  be  extracted  by  cutting  through  the 
decidual  membrane,  either  from  one  side  or  the  other,  and  opening 
in  this  way  the  special  cavity  in  which  it  has  been  inclosed. 

During  the  formation  of  the  decidua  reflexa,  the  entire  Ggg,  as 
well  as  the  body  of  the  uterus  which  contains  it,  has  considerably- 
enlarged.  That  portion  of  the  uterine  mucous  membrane  situated 
immediately  underneath  the  Qgg,  and  to  which  the  egg  first  became 
attached,  has  also  continued  to  increase  in  thickness  and  vascularity. 
The  remainder  of  the  decidua  vera,  however,  ceases  to  grow  as 
rapidly  as  before,  and  no  longer  keeps  pace  with  the  increasing 
size  of  the  egg  and  of  the  uterus.  It  is  still  very  thick  and  vascu- 
lar at  the  end  of  the  third  month ;  but  after  that  period  it  becomes 
comparatively  thinner  and  less  glandular  in  appearance,  while  the 
unusual  activity  of  growth  and  development  is  concentrated  in  the 
egg,  and  in  that  portion  of  the  uterine  mucous  membrane  which  is 
in  immediate  contact  with  it. 

Let  us  now  see  in  what  manner  the  egg  becomes  attached  to  the 
decidual  membrane,  so  as  to  derive  from  it  the  requisite  supply  of 
nutritious  material.  It  must  be  recollected  that,  while  the  above 
changes  have  been  taking  place  in  the  walls  of  the  uterus,  the 


FORMATION    OF    THE    EECIDUA. 


619 


Fig.  222. 


formation  of  the  embryo  in  the  egg,  and  the  development  of  the 
amnion  and  chorion  have  been  going  on  simultaneously.  Soon 
after  the  entrance  of  the  egg  into  the  uterine  cavity,  its  external 
investing  membrane  becomes  covered  with  projecting  filaments,  or 
viliosities,  as  previously  described.  (Chap.  X.)  These  villosities, 
which  are  at  first,  as  we  have  seen,  solid  and  non-vascular,  insinuate 
themselves,  as  they  grow,  into  the  uterine  tubules,  or  between  the 
folds  of  the  decidual  surface  with  which  the  egg  is  in  contact,  pene- 
trating in  this  way  into  little  cavities  or  follicles  of  the  uterine 
mucous  membrane,  formed  either  from  the  cavities  of  the  tubules 
themselves,  or  by  the  adjacent  surfaces  of  minute  projecting  folds. 
When  the  formation  of  the  decidua  reflexa  is  accomplished,  the 
chorion  has  already  become  uniformly 
shaggy ;  and  its  villosities,  spreading  in  all 
directions  from  its  external  surface,  pene- 
trate everywhere  into  the  follicles  above  de- 
scribed, both  of  the  decidua  vera  underneath 
it  and  the  contiguous  surface  of  the  decidua 
reflexa  with  which  it  is  covered.  (Fig.  222.) 
In  this  way  the  egg  becomes  entangled 
with  the  decidua,  and  cannot  then  be  read- 
ily separated  from  it,  without  rupturing 
some  of  the  filaments  which  have  grown 
from  its  surface,  and  have  been  received 
into  the  cavity  of  the  follicles.  The  nu- 
tritious fluids,  exuded  from  the  soft  and 
glandular  textures  of  the  decidua,  are  now 
readily  imbibed  by  the  villosities  of  the  chorion ;  and  a  more  rapid 
supply  of  nourishment  is  thus  provided,  corresponding  in  abun- 
dance with  the  increased  and  increasing  size  of  the  egg. 

Very  soon,  however,  a  still  greater  activity  of  absorption  be- 
comes necessary ;  and,  as  we  have  seen  in  a  preceding  chapter,  the 
external  membrane  of  the  egg  becomes  vascular  by  the  formation 
of  the  allantoic  bloodvessels,  which  emerge  from  the  body  of  the 
foetus,  to  ramify  in  the  chorion,  and  penetrate  everywhere  into  the 
villosities  with  which  it  is  covered.  Each  villosity,  then,  as  it  lies 
imbedded  in  its  uterine  follicle,  contains  a  vascular  loop  through 
which  the  foetal  blood  circulates,  increasing  the  rapidity  with  which 
ab.sorption  and  exhalation  take  place. 

Subsequently,  furthermore,  these  vascular  tufts,  which  are  at  first 
uniformly  abundant  throughout  the  whole  extent  of  the  chorion, 


Impregnated  Utsritb; 
showing  connection  between  vil- 
losities of  chorion  and  deciduai 
membranes. 


620      DEVELOPMENT    OF    UTERINE    MUCOUS    MEMBRANE. 


Fig.  223. 


disappear  over  a  portion  of  its  surface,  while  they  at  the  same  time 
become  concentrated  and  still  further  developed  at  a  particular 
spot,  the  situation  of  the  future  placenta,  (Fig.  223.)     This  is  the 

spot  at  which  the  egg  is  in  contact  with 
the  decidua  vera.  Here,  therefore,  both 
the  decidual  membrane  and  the  tufts 
of  the  chorion  continue  to  increase  in 
thickness  and  vascularity ;  while  else- 
where, over  the  prominent  portion  of 
the  egg,  the  chorion  not  only  becomes 
bare  of  villosities,  and  comparatively 
destitute  of  vessels,  but  the  decidua  re- 
flexa,  which  is  in  contact  with  it,  also 
loses  its  activity  of  growth,  and  be- 
comes expanded  into  a  thin  layer,  nearly 
destitute  of  vessels,  and  without  any 
remaining  trace  of  tubules  or  follicles. 
The  uterine  mucous  membrane  is 
therefore  developed,  during  the  process 
of  gestation,  in  such  a  way  as  to  provide 
for  the  nourishment  of  the  foetus  in  the  different  stages  of  its  growth. 
At  first,  the  whole  of  it  is  uniformly  increased  in  thickness  (decidua 
vera).  Next,  a  portion  of  it  grows  upward  around  the  egg,  and 
covers  its  projecting  surface  (decidua  reflexa).  Afterward,  both  the 
decidua  reflexa  and  the  greater  part  of  the  decidua  vera  diminish 
in  the  activity  of  their  growth,  and  lose  their  importance  as  a  means 
of  nourishment  for  the  egg ;  while  that  part  which  is  in  contact  with 
the  vascular  tufts  of  the  chorion  continues  to  grow,  becoming  ex- 
ceedingly developed,  and  taking  an  active  part  in  the  formation  of 
the  placenta. 

In  the  following  chapter,  we  shall  examine  more  particularly  the 
structure  and  development  of  the  placenta  itself,  and  of  those  parts 
which  are  immediately  connected  with  it. 


Pregnant  UxERtrs;  showing 
formation  of  placenta,  hj  the  united 
development  of  a  portion  of  the  de- 
cldna  and  the  TlUositles  of  the  cho- 


THE    PLACENTA.  621 


CHAPTER    XII. 

THE    PLACENTA. 

We  have  shown  in  the  preceding  chapters  that  the  foetus,  during 
its  development,  depends  for  its  supply  of  nutriment  upon  the  lining 
membrane  of  the  maternal  uterus ;  and  that  the  nutriment,  so  sup- 
plied, is  absorbed  by  the  bloodvessels  of  the  chorion,  and  transported 
in  this  way  into  the  circulation  of  the  foetus.  In  all  instances,  ac- 
cordingly, in  which  the  development  of  the  foetus  takes  place  within 
the  body  of  the  parent,  it  is  provided  for  by  the  relation  thus  esta- 
blished between  two  sets  of  membranes;  namely,  the  maternal 
membranes  which  supply  nourishment,  and  the  foetal  membranes 
which  absorb  it. 

In  some  species  of  animals,  the  connection  between  the  maternal 
and  foetal  membranes  is  exceedingly  simple.  In  the  pig,  for  ex- 
ample, the  uterine  mucous  membrane  is  everywhere  uniformly 
vascular ;  its  only  peculiarity  consisting  in  the  presence  of  nume- 
rous transverse  folds,  which  project  from  its  surface,  analogous  to 
the  valvule  conniventes  of  the  small  intestine.  The  external  in- 
vesting membrane  of  the  egg,  which  is  the  allantois,  is  also  smooth 
and  uniformly  vascular  like  the  other.  No  special  development  of 
tissue  or  of  vessels  occurs  at  any  part  of  these  membranes,  and 
no  direct  adhesion  takes  place  between  them;  but  the  vascular 
allantois  or  chorion  of  the  foetus  is  everywhere  closely  applied  to 
the  vascular  mucous  membrane  of  the  maternal  uterus,  each  of  the 
two  contiguous  surfaces  following  the  undulations  presented  by  the 
other,  (Fig.  224.)  By  this  arrangement,  transudation  and  absorp- 
tion take  place  from  the  bloodvessels  of  the  mother  to  those  of  the 
foetus,  in  sufficient  quantity  to  provide  for  the  nutrition  of  the  latter. 
When  parturition  takes  place,  accordingly,  in  these  animals,  a  very 
moderate  contraction  of  the  uterus  is  sufficient  to  expel  its  contents. 
The  egg,  displaced  from  its  original  position,  slides  easily  forward 
over  the  surface  of  the  uterine  mucous  membrane,  and  is"  at  last 
discharged  without  any  hemorrhage  or  laceration  of  connecting 
parts.  In  other  instances,  however,  the  development  of  the  foetus 
requires  a  more  elaborate  arrangement  of  the  vascular  membranes. 


622 


THE    PLACENTA. 


In  the  cow,  for  example,  the  external  membrane  of  the  egg,  beside 
being  everywhere  supplied  with  branching  vessels,  presents  upon 

Fig.  224. 


FcETAL  Via,  with  Its  membranes,  contained  in  cavity  of  uterus. — a,  a,  b,  b.  Walls  of  nterns. 
c,  c.  Cavity  of  uterus,    d.  Amaion.    e,  e.  AUantois. 

various  points  of  its  surface  no  less  than  from  seventy  to  eighty  oval 
spots,  at  each  of  which  the  vessels  of  the  chorion  are  developed  into 
abundant  tufted  prominences,  hanging  from  its  exterior  in  thick, 
velvety,  vascular  masses.  At  each  point  of  the  uterine  mucous  mem- 
brane, corresponding  with  one  of  these  tufted  masses,  the  maternal 
bloodvessels  are  developed  in  a  similar  manner,  projecting  into  the 
uterine  cavity  as  a  flattened  rounded  mass  or  cake ;  which,  with  that 
part  of  the  foetal  chorion  which  is  adherent  to  it,  is  known  by  the 


Fig.  225. 


Cotyledon  of  Cow's  Utekus.— a,  a.  Surface  of  foetal  chorion.  b,b.  Bloodvessels  of  foeta-l 
chorion,  d,  d.  Bloodvessels  of  uterine  mucous  membrane,  c,  c.  Surface  of  uterine  mucous  mem- 
brane. 

name  of  the  Cotyledon.  Each  cotyledon  forms,  therefore,  a  little 
placenta.  (Fig.  225.)  In  its  substance  the  tufted  vascalar  loops 
coming  from  the  uterine  mucous  membrane  {d,  d)  are  entangled 


TllE    PLACENTA.  623 

witli  those  coming  from  tlie  membranes  of  the  foetus  {b,  I).  There 
is  no  absolute  adhesion  between  the  two  sets  of  vessels,  but  only 
an  interlacement  of  their  ramified  extremities;  and,  with  a  little 
care  in  manipulation,  the  foetal  portion  of  the  cotyledon  may  be 
extricated  from  the  maternal  portion,  without  lacerating  either.  In 
consequence,  however,  of  this  intricate  interlacement  of  the  vessels, 
transudation  of  fluids  will  evidently  take  place  with  great  readiness, 
from  one  system  to  the  other. 

The  form  of  placenta,  therefore,  met  with  in  these  animals,  is  one 
in  which  the  bloodvessels  of  the  foetal  chorion  are  simply  entangled 
with  those  of  the  uterine  mucous  membrane.  In  the  human  sub- 
ject, the  structure  of  the  placenta  is  a  little  more  complicated, 
though  the  main  principles  of  its  formation  are  the  same  as  in  the 
above  instances. 

From  what  has  been  said  in  the  foregoing  chapters,  it  appears 
that  in  the  human  subject,  as  well  as  in  the  lower  animals,  the 
placenta  is  formed  partly  by  the  vascular  tufts  of  the  chorion, 
and  partly  by  the  thickened  mucous  membrane  of  the  uterus  in 
which  they  are  entangled.  During  the  third  month,  those  portions 
of  the  chorion  and  decidua  which  are  destined  to  undergo  this 
transformation  become  more  or  less  distinctly  limited  in  their  form 
and  dimensions ;  and  a  thickened  vascular  mass,  partly  maternal 
and  partly  foetal  in  its  origin,  shows  itself  at  the  spot  where  the 
placenta  is  afterward  to  be  developed.  This  mass  is  constituted  in 
the  following  manner. 

It  will  be  recollected  that  the  villi  of  the  chorion,  when  first 
formed,  penetrate  into  follicles  situated  in  the  substance  of  the 
uterine  mucous  membrane;  and  that  after  they  have  become  vas- 
cular, they  rapidly  elongate  and  are  developed  into  tufted  ramifi- 
cations of  bloodvessels,  each  one  of  which  turns  upon  itself  in  a 
loop  at  the  end  of  the  villus.  At  the  same  time  the  uterine  follicle, 
into  whicli  the  villus  has  penetrated,  enlarges  to  a  similar  extent ; 
sending  out  branching  diverticula,  corresponding  with  the  multi- 
plied ramifications  of  the  villus.  In  fact,  the  growth  of  the  follicle 
and  that  of  the  villus  go  on  simultaneously,  and  keep  pace  with 
each  other;  the  latter  constantly  advancing  as  the  cavity  of  the 
former  enlarges. 

But  it  is  not  only  the  uterine  follicles  which  increase  in  size  and 
in  complication  of  structure  at  this  period.  The  capillary  blood- 
vessels, which  lie  between  them  and  ramify  over  their  exterior, 
also  become  unusually  developed.  They  enlarge  and  inosculate 
freely  with  each  other;  so  that  every  uterine  follicle  is  soon  covered 


624 


THE    PLACENTA. 


•with,  an  abundant  network  of  dilated  capillaries,  derived  from  the 
bloodvessels  of  the  original  decidua.  At  this  time,  therefore,  each 
vascular  loop  of  the  foetal  chorion  is  covered,  first,  with  a  layer 
forming  the  wall  of  the  villus.  This  is  in  contact  with  the  lining 
membrane  of  a  uterine  follicle,  and  outside  of  this  again  are  the 
capillary  vessels  of  the  uterine  mucous  membrane;  so  that  two 
distinct  membranes  intervene  between  the  walls  of  the  foetal  capil- 
laries on  the  one  hand  and  those  of  the  maternal  capillaries  on  the 
other,  and  all  transudation  must  take  place  through  the  substance 
of  these  two  membranes. 

As  the  formation  of  the  placenta  goes  on,  the  anatomical  arrange- 
ment of  the  foetal  vessel  remains  the  same.  They  continue  to 
form  vascular  loops,  penetrating  deeply  into  the  decidual  mem- 
brane; only  they  become  constantly  more  elongated,  and  their 
ramifications  more  abundant  and  tortuous.  The  maternal  capilla- 
ries, however,  situated  on  the  outside  of  the  uterine  follicles,  become 
considerably  altered  in  their  anatomical  relations.  They  enlarge 
excessively ;  and,  by  encroaching  constantly  upon  the  little  islets 
or  spaces  between  them,  fuse  successively  with  each  other;  and, 
losing  gradually  in  this  way  the  characters  of  a  capillary  network, 

become     dilated     into     wide 
Fig.  226.  sinuses,    which     communicate 

freely  with  the  enlarged  vessels 
in  the  muscular  walls  of  the 
uterus.  As  the  original  capil- 
lary plexus  occupied  the  entire 
thickness  of  the  hypertrophied 
decidua,  the  vascular  sinuses, 
into  which  it  is  thus  converted, 
are  equally  extensive.  They 
commence  at  the  inferior  sur- 
face of  the  placenta,  where  it  is 
in  contact  with  the  muscular 
walls  of  the  uterus,  and  extend 
through  its  whole  thickness, 
quite  up  to  the  surface  of  the 
foetal  chorion. 
As  the  maternal  sinuses  grow  upward,  the  vascular  tufts  of  the 
chorion  grow  downward,  and  extend  also  through  the  entire  thick- 
ness of  the  placenta.  At  this  period,  the  development  of  the  blood- 
vessels, both  in  the  foetal  and  maternal  portions  of  the  placenta,  is 
so  excessive  that  all  the  other  tissues,  which  originally  co-existed 


Extremity  of  Fcetal  Tuft,  from  hnman  pla- 
centa at  term,  in  its  recent  condition,  a,  a.  Capil- 
lary bloodvessels.     Magnified  135  diameters. 


THE    PLACENTA.  625 

•witli  them,  become  retrograde  and  disappear  almost  altogether.  If 
a  villus  from  the  foetal  portion  of  the  placenta  be  examined  at  this 
time  by  transparency,  in  the  fresh  condition  (Fig.  226)  it  will  be 
seen  that  its  bloodvessels  are  covered  only  with  a  layer  of  homo- 
geneous, or  finely  granular  material,  35'tro  ^^  ^^  i^^^  i^  thickness, 
in  which  are  imbedded  small  oval-shaped  nuclei,  similar  to  those 
seen  at  an  earlier  period  in  the  villosities  of  the  chorion.  The  vil- 
losities  of  the  chorion  are  now,  therefore,  hardly  anything  more 
than  ramified  and  tortuous  vascular  loops ; 
the  remaining  substance  of  the  villi  hav-  ^ig-  227. 

ing  been  atrophied  and  absorbed  in  the 
excessive  growth  of  the  bloodvessels,  the 
abundance  and  development  of  which 
can  be  readily  shown  by  injection  from 
the  umbilical  arteries.  (Fig.  227.)  The 
uterine  follicles  have  at  the  same  time 
lost  all  trace  of  their  original  structure, 
and  have  become  mere  vascular  sinuses, 
into  which  the  tufted  foetal  bloodvessels 
are  received,  as  the  villosities  of  the  cho- 
rion were  at  first  received  into  the  uterine       Extremity  of  F(etal  tdft  of 

„  ,,.    -  human  placenta;  from  an  injected 

lOillCieS.  speeimen.   Magnified  40  diameters. 

Finally,  the  walls  of  the  foetal  blood- 
vessels having  come  into  close  contact  with  the  walls  of  the  maternal 
sinuses,  the  two  become  adherent  and  fuse  together ;  so  that  a  time 
at  last  arrives,  when  we  can  no  longer  separate  the  foetal  vessels,  in 
the  substance  of  the  placenta,  from  the  maternal  sinuses,  without 
lacerating  either  the  one  or  the  other,  owing  to  the  secondary 
adhesion  which  has  taken  place  between  them. 

The  placenta,  therefore,  when  perfectly  formed,  has  the  structure 
which  is  shown  in  the  accompanying  diagram  (Fig.  228),  repre- 
senting a  vertical  section  of  the  organ  through  its  entire  thickness. 
At  a,  a,  is  seen  the  chorion,  receiving  the  umbilical  vessels  from  the 
body  of  the  foetus  through  the  umbilical  cord,  and  sending  out  its 
compound  and  ramified  vascular  tufts  into  the  substance  of  the 
placenta.  At  b,  h,  is  the  attached  surface  of  the  decidua,  or  uterine 
mucous  membrane ;  and  at  c,  c,  c,  c,  are  the  orifices  of  uterine  ves- 
sels which  penetrate  it  from  below.  These  vessels  enter  the  placenta 
in  an  extremely  oblique  direction,  though  they  are  represented  in 
the  diagram,  for  the  sake  of  distinctness,  as  nearly  perpendicular. 
When  they  have  once  penetrated,  however,  the  lower  portion  of 
40 


626 


THE    PLACENTA. 


the  decidua,  thej  immediately  dilate   into  the  placental   sinuses 
(represented,  in  the  diagram,  in  black),  which  extend  through  the 

Fig.  228. 


Vertical  section  of  Placenta,  showing  arrangement  of  maternal  and  fetal  vessels.    a,a.  Cho- 
rion.   6,  b.  Decidua.    c,  c,  c,  c.  Orifices  of  uterine  sinuses. 

whole  thickness  of  the  organ,  closely  embracing  all  the  ramifica- 
tions of  the  foetal  tufts.  It  will  be  seen,  therefore,  that  the  placenta, 
arrived  at  this  stage  of  completion,  is  composed  essentially  of  no- 
thino-  but  bloodvessels.  No  other  tissues  enter  into  its  structure ; 
for  all  those  which  it  originally  contained  have  disappeared,  except- 
ing the  bloodvessels  of  the  foetus,  entangled  with  and  adherent  to 
the  bloodvessels  of  the  mother. 

There  is,  however,  no  direct  communication  between  the  foetal 
and  maternal  vessels.  The  blood  of  the  foetus  is  always  separated 
from  the  blood  of  the  mother  by  a  membrane  which  has  resulted 
from  the  successive  union  and  fusion  of  four  different  membranes, 
viz.,  first,  the  membrane  of  the  foetal  villus ;  secondly,  that  of  the 
uterine  follicle ;  thirdly,  the  wall  of  the  foetal  bloodvessel ;  and, 
fourthly,  the  wall  of  the  uterine  sinus.  The  single  membrane,  how- 
ever, into  which  these  four  finally  coalesce,  is  extremely  thin,  as 
we  have  seen,  and  of  enormous  extent,  owing  to  the  extremely 
abundant  branching  and  subdivision  of  the  foetal  tufts.  These  tufts, 
accordingly,  in  which  the  blood  of  the  foetus  circulates,  are  bathed 
everywhere,  in  the  placental  sinuses,  with  the  blood  of  the  mother ; 
and  the  processes  of  endosmosis  and  exosmosis,  of  exhalation  and 
absorption,  go  on  between  the  two  with  the  greatest  possible 
activity. 


THE    PLACENTA.  627 

It  is  very  easy  to  demonstrate  the  arrangement  of  tlie  foetal 
tufts  in  the  human  placenta.  They  can  be  readily  seen  by  the 
naked  eye,  and  may  be  easily  traced  from  their  attachment  at  the 
under  surface  of  the  chorion  to  their  termination  near  the  uterine 
surface  of  the  placenta.  The  anatomical  disposition  of  the  pla- 
cental sinuses,  however,  is  much  more  dif&cult  of  examination. 
During  life,  and  while  the  placenta  is  still  attached  to  the  uterus, 
they  are  filled,  of  course,  with  the  blood  of  the  mother,  and  occupy 
fully  one-half  the  entire  mass  of  the  placenta.  But  when  the  pla- 
centa is  detached,  the  maternal  vessels  belonging  to  it  are  torn  off 
at  their  necks  (Fig.  228,  c,  c,  c,  c),  and  the  sinuses,  being  then 
emptied  of  blood  by  the  compression  to  which  the  placenta  is  sub- 
jected, are  apparently  obliterated ;  and  the  foetal  tufts,  falling  to- 
gether and  lying  in  contact  with  each  other,  appear  to  constitute 
the  whole  of  the  placental  mass.  The  existence  of  the  placental 
sinuses,  however,  and  their  true  extent,  may  be  satisfactorily  de- 
monstrated in  the  following  manner. 

If  we  take  the  uterus  of  a  woman  who  has  died  undelivered  at 
the  full  term  or  thereabout,  and  open  it  in  such  a  way  as  to  avoid 
wounding  the  placenta,  this  organ  will  be  seen  remaining  attached 
to  the  uterine  surface,  with  all  its  vascular  connections  complete. 
Let  the  foetus  now  be  removed  by  dividing  the  umbilical  cord,  and 
the  uterus,  with  the  placenta  attached,  placed  under  water,  with  its 
internal  surface  uppermost.  If  the  end  of  a  blowpipe  be  now 
introduced  into  one  of  the  divided  vessels  of  the  uterine  walls,  and 
air  forced  in  by  gentle  insufflation,  we  can  easily  inflate,  first,  the 
venous  sinuses  of  the  uterus  itself,  and  next,  the  deeper  portions 
of  the  placenta ;  and  lastly,  the  bubbles  of  air  insinuate  themselves 
everywhere  between  the  foetal  tufts,  and  appear  in  the  most  super- 
ficial portions  of  the  placenta,  immediately  underneath  the  trans- 
parent chorion  (a,  a,  Fig.  228);  thus  showing  that  the  placental 
sinuses,  which  freely  communicate  with  the  uterine  vessels,  really 
occupy  the  entire  thickness  of  the  placenta,  and  are  equally  exten- 
sive with  the  tufts  of  the  chorion.  We  have  verified  this  fact  in 
the  above  manner,  on  four  different  occasions,  and  in  the  presence 
of  Prof.  C.  E.  Gilman,  Prof  Geo.  T.  Elliot,  Dr.  Henry  B.'  Sands, 
Prof  T.  G.  Thomas,  Dr.  T.  C.  Finnell,  and  various  other  medical 
gentlemen  of  New  York. 

If  the  placenta  be  now  detached  and  examined  separately,  it  will 
be  found  to  present  upon  its  uterine  surface  a  number  of  openings 
which   are   extremely  oblique   in   their   position,  and  which  are 


628  THE    PLACENTA. 

accordingly  bounded  on  one  side  by  a  very  thin,  projecting,  cres- 
centic  edge.  These  are  the  orifices  of  the  uterine  vessels,  passing 
into  the  placenta  and  torn  off  at  their  necks,  as  above  described ; 
and  by  carefully  following  them  with  the  probe  and  scissors,  they 
are  found  to  lead  at  once  into  extensive  empty  cavities  (the  pla- 
cental sinuses),  situated  between  the  foetal  tufts.  We  have  already 
shown  that  these  cavities  are  filled  during  life  with  the  maternal 
blood ;  and  there  is  every  reason  to  believe  that  before  delivery, 
and  while  the  circulation  is  going  on,  the  placenta  is  at  least  twice 
as  large  as  after  it  has  been  detached  and  expelled  from  the  uterus. 

The  placenta,  accordingly,  is  a  double  organ,  formed  partly  by 
the  chorion  and  partly  by  the  decidua ;  and  consisting  of  maternal 
and  foetal  bloodvessels,  inextricably  entangled  and  united  with  each 
other. 

The  part  which  this  organ  takes  in  the  development  of  the  foetus 
is  an  exceedingly  important  one.  From  the  date  of  its  formation, 
at  about  the  beginning  of  the  fourth  month,  it  constitutes  the  onl_y 
channel  through  which  nourishment  is  conveyed  from  the  mother 
to  the  foetus.  The  nutritious  materials,  which  circulate  in  abun- 
dance in  the  blood  of  the  maternal  sinuses,  pass  through  the  inter- 
vening membrane  by  endosmosis,  and  enter  the  blood  of  the  foetus. 
The  healthy  or  injurious  regimen,  to  which  the  mother  is  subjected, 
will  accordingly  exert  an  almost  immediate  influence- upon  the 
child.  Even  medicinal  substances,  taken  by  the  mother  and  ab- 
sorbed into  her  circulation,  may  readily  transude  through  the  pla- 
cental vessels ;  and  they  have  been  known  in  this  way  to  exert  a 
specific  effect  upon  the  foetal  organization. 

The  placenta  is,  furthermore,  an  organ  of  exhalation  as  well  as 
of  absorption.  The  excrementitious  substances,  produced  in  the 
circulation  of  the  foetus,  are  undoubtedly  in  great  measure  disposed 
of  by  transudation  through  the  walls  of  the  placental  vessels,  to  be 
afterward  discharged  by  the  excretory  organs  of  the  mother.  The 
system  of  the  mother  may  therefore  be  affected  in  this  manner  by 
influences  derived  from  the  foetus.  It  has  been  remarked  more 
than  once,  in  the  lower  animals,  that  when  the  female  has  two  sue 
cessive  litters  of  young  by  different  males,  the  young  of  the  second 
litter  will  sometimes  bear  marks  resembling  those  of  the  first  male. 
In  these  instances,  the  peculiar  influence  which  produces  the  ex 
ternal  mark  must  have  been  transmitted  by  the  first  male  directly 
to  the  foetus,  from  the  foetus  to  the  mother,  and  from  the  mother  to 
»be  foetus  of  the  second  litter. 


THE    PLACENTA.  629 

It  is  also  through  the  placental  circulation  that  those  disturbing 
eflfects  are  produced  upon  the  nutrition  of  the  foetus,  which  result 
from  sudden  shocks  or  injuries  inflicted  upon  the  mother.  There  is 
now  little  room  for  doubt  that  various  deformities  and  deficiencies  of 
the  foetus,  conformably  to  the  popular  belief,  do  really  originate,  in 
certain  cases,  from  nervous  impressions,  such  as  disgust,  fear  or  anger, 
experienced  by  the  mother.  The  mode  in  which  these  effects  may 
be  produced  is  readily  understood  from  what  has  been  said  above 
of  the  anatomy  and  functions  of  the  placenta.  We  know  very  well 
how  easily  nervous  impressions  will  disturb  the  circulation  in  the 
brain,  the  face,  the  lungs,  &c. ;  and  the  uterine  circulation  is  quite 
as  readily  influenced  by  similar  causes,  as  physicians  see  every  day 
in  cases  of  amenorrhoea,  menorrhagia,  &c.  If  a  nervous  shock  may 
excite  premature  contraction  in  the  muscular  fibres  of  the  pregnant 
uterus  and  produce  abortion,  as  not  unfrequently  happens,  it  is  cer- 
tainly capable  of  disturbing  the  course  of  the  circulation  through 
the  same  organ.  But  the  foetal  circulation  is  dependent,  to  a  great 
extent,  on  the  maternal.  Since  the  two  sets  of  vessels  are  so  closely 
entwined  in  the  placenta,  and  since  the  foetal  blood  has  here  much 
the  same  relation  to  the  maternal,  that  the  blood  in  the  pulmonary 
capillaries  has  to  the  air  in  the  air- vesicles,  it  will  be  liable  to  de- 
rangement from  similar  causes.  If  the  circulation  of  air  through 
the  pulmonary  tubes  be  suspended,  that  of  the  blood  through 
the  general  capillaries  is  disturbed  also.  In  the  same  way,  what- 
ever arrests  or  disturbs  the  circulation  through  the  vessels  of  the 
maternal  uterus  must  necessarily  be  liable  to  interfere  with  that 
in  the  foetal  capillaries  forming  part  of  the  placenta.  And  lastly, 
as  the  nutrition  of  the  foetus  is  provided  for  wholly  by  the  placenta, 
it  will  of  course  suffer  immediately  from  any  such  disturbance  of 
the  placental  circulation.  These  effects  may  be  manifested  either 
in  the  general  atrophy  and  death  of  the  foetus ;  or,  if  the  disturbing 
cause  be  slight,  in  the  atrophy  or  imperfect  development  of  par- 
ticular parts ;  just  as,  in  the  adult,  a  morbid  cause  operating  through 
the  entire  system,  may  be  first  or  even  exclusively  manifested  in 
some  particular  organ,  which  is  more  sensitive  to  its  influence  than 
other  parts. 

The  placenta  must  accordingly  be  regarded  as  an  organ  which 
performs,  during  intra-uterine  life,  offices  similar  to  those  of  the 
lungs  and  the  intestine  after  birth.  It  absorbs  nourishment,  reno- 
vates the  blood,  and  discharges  by  exhalation  various  excrementi 
tious  matters,  which  originate  in  the  processes  of  foetal  nutrition. 


630 


DISCHAEGE    OF   THE    OVUM. 


CHAPTER   XIII. 


DISCHARGE    OF    THE    OYUM,    AND    RETROGRADE 
DEVELOPMENT  (INVOLUTION)  OF  THE  UTERUS. 

During  the  growtli  of  the  ovum  and  the  formation  of  the  pla- 
cental structures,  the  muscular  substance  of  the  uterus  also  increases 
in  thickness,  while  the  whole  organ  enlarges,  in  order  to  accommo- 
date the  growing  foetus  and  its  appendages.  The  relative  positions 
of  the  amnion  and  chorion,  furthermore,  undergo  a  change  during 
the  latter  periods  of  gestation,  and  the  umbilical  cord  becomes 
developed,  at  the  same  time,  in  the  following  manner. 

In  the  earlier  periods  of  foetal  life,  the  umbilical  cord  consists 
simply  of  that  portion  of  the  allantois  lying  next  the  abdomen.  It 
is  then  very  short,  and  contains  the  umbilical  vessels  running  in  a 
nearly  straight  course,  and  parallel  with  each  other,  from  the  abdo- 
men of  the  foetus  to  the  external  portions  of  the  chorion.  At  this 
time  the  amnion  closely  invests  the  body  of  the  foetus,  so  that  the 

size  of  its  cavity  is  but  little  larger 
^'S-  229-  than  that  of  the  foetus.  (Fig.  229.) 

The  space  between  the  amnion 
and  the  chorion  is  then  occupied 
by  an  amorphous  gelatinous  ma- 
terial, in  which  lies  imbedded  the 
umbilical  vesicle. 

Afterward,  however,  the  am- 
nion enlarges  faster  than  the  cho- 
rion, and  encroaches  upon  the 
layer  of  gelatinous  matter  situated 
between  the  two  (Fig.  230),  at 
the  same  time  that  an  albuminous 
fluid,  the  "  amniotic  fluid,"  is  ex- 
uded into  its  cavity,  in  constantly 
increasing  quantity.  Subsequently,  the  gelatinous  layer,  above  de- 
scribed, altogether  disappears,  and  the  amnion,  at  about  the  begin- 


HuMAN  Ovum  about  the  end  of  the  first 
month.— 1.  Umbilical  vesicle.  2.  Amnion.  3. 
Chorion. 


ENLARGEMENT    OF    THE    AMNION. 


631 


Human  Ovum  at  end  of  third  mouth  ;  showing 
enlargement  of  amnion. 


ning  of  tlie  fifth  month,  comes  in  contact  with  the  internal  surface 

of  the  chorion.     Finally,  toward  the  end  of  gestation,  the  contact 

becomes  so  close  between  these 

two  membranes  that  they  are  Fig-  230. 

partially    adherent    to    each 

other,  and  it  requires  a  little 

care  to  separate  them  without 

laceration. 

The  quantity  of  the  amniotic 
fluid  continues  to  increase  dur- 
ing the  latter  period  of  gesta- 
tion in  order  to  accommodate 
the  movements  of  the  foetus. 
These  movements  begin  to  be 
perceptible  about  the  fifth 
month,  at  which  time  the 
muscular  system  has  already 

attained  a  considerable  degree  of  development,  but  become  after- 
ward more  frequent  and  more  strongly  pronounced.  The  space 
and  freedom  requisite  for  these  movements  are  provided  for  by  the 
fluid  accumulated  in  the  cavity  of  the  amnion. 

The  umbilical  cord  elongates,  at  the  same  time,  in  proportion  to 
the  increasing  size  of  the  amniotic  cavity.  During  its  growth,  it 
becomes  spirally  twisted  from  right  to  left,  the  two  umbilical  aite- 
ries  winding  round  the  vein  in  the  same  direction.  The  gelatinous 
matter,  as  already  described  as  existing  between  the  amnion  and 
chorion,  while  it  disappears  elsewhere,  accumulates  in  the  cord  in 
considerable  quantity,  covering  the  vessels  with  a  thick,  elastic  en- 
velope, which  protects  them  from  injury  and  prevents  their  being 
accidentally  compressed  or  obliterated.  The  whole  is  covered  by  a 
portion  of  the  amnion,  which  is  connected  at  one  extremity  with  the 
integument  of  the  abdomen,  and  invests  the  whole  of  the  cord  with 
a  continuous  sheath,  like  the  finger  of  a  glove.  (Fig.  231.) 

The  cord  also  contains,  for  a  certain  period,  the  pedicle  or  stem 
of  the  umbilical  vesicle.  The  situation  of  this  vesicle,  it  will  be 
recollected,  is  always  between  the  chorion  and  the  amnion.  Its 
pedicle  gradually  elongates  with  the  growth  of  the  umbilical  cord ; 
and  the  vesicle  itself,  which  generally  disappears  soon  after  the 
third  month,  sometimes  remains  as  late  as  the  fifth,  sixth,  or  seventh. 
According  to  Prof.  Mayer,  of  Bonn,  it  may  even  be  found,  by  care- 
ful search,  at  the  termination  of  pregnancy.     When  discovered  in 


632  DISCHARGE    OF   THE    OVUM.      . 

the  middle  and  latter  periods  of  gestation,  it  presents  itself  as  a 
small,  flattened,  and  shrivelled  vesicle,  situated  underneath  the 
amnion,  at  a  variable  distance  from  the  insertion  of  the  umbilical 
cord.  A  minute  bloodvessel  is  often  seen  running  to  it  from  the 
cord,  and  ramifying  upon  its  surface. 

Fie?.  231. 


Gravid  Human  IlTEBtTs  asdContekts,  showing  the  relations  of  the  cord,  placenta,  mem, 
branes,  &c,  about  the  end  of  the  seventh  month. — 1.  Deciduavera.  2..Decidaa  reflexa.  3.  Chorion. 
4.  Amnion. 

The  decidua  reflexa,  during  the  latter  months  of  pregnancy,  is 
constantly  distended  and  pushed  back  by  the  increasing  size  of  the 
egg ;  so  that  it  is  finally  pressed  closely  against  the  opposite  surface 
of  the  decidua  vera,  which  still  lines  the  greater  part  of  the  uterine 
cavity.  By  the  end  of  the  seventh  month,  the  opposite  surfaces 
of  the  decidua  vera  and  reflexa  are  in  complete  contact  with  each 
other,  though  still  distinct  and  capable  of  being  separated  without 
difficulty.  After  that  time,  they  fuse  together  and  become  con- 
founded with  each  other ;  the  two  at  last  forming  only  a  single, 
thin,  friable,  semi- opaque  layer,  in  which  no  trace-  of  their  original 
glandular  structure  can  be  discovered. 

This  is  the  condition  of  things  at  the  termination  of  pregnancy. 
Then,  the  time  having  arrived  for  parturition  to  take  place,  the 
hypertrophied  muscular  walls  of  the  uterus  contract  forcibly  upon 
its  contents,  and  the  egg  is  discharged,  together  with  the  whole  of 
the  decidual  uterine  mucous  membrane. 


SEPARATION    OF    THE    PLACENTA.  633 

In  tlie  human  subject,  as  well  as  in  most  quadrupeds,  the  mem- 
branes of  the  egg  are  usually  ruptured  during  the  process  of  par- 
turition ;  and  the  foetus  escapes  first,  the  placenta  and  the  rest  of 
the  appendages  following  a  few  moments  afterward.  Occasionally, 
however,  even  in  the  human  subject,  the  egg  is  discharged  entire, 
and  the  foetus  liberated  afterward  by  the  laceration  of  the  mem- 
branes. In  each  case,  however,  the  mode  of  separation  and  expul- 
sion is  in  all  particulars  the  same. 

The  process  of  parturition,  therefore,  consists  essentially  in  a 
separation  of  the  decidual  membrane,  which,  on  being  discharged, 
brings  away  the  ovum  with  it.  The  greater  part  of  the  decidua 
vera,  having  fallen  into  a  state  of  atrophy  during  the  latter  months 
of  pregnancy,  is  by  this  time  nearly  destitute  of  vessels,  and  sepa- 
rates, accordingly,  without  any  perceptible  hemorrhage.  That  por- 
tion, however,  which  enters  into  the  formation  of  the  placenta,  is, 
on  the  contrary,  excessively  vascular ;  and  when  the  placenta  is 
separated,  and  its  maternal  vessels  torn  off  at  their  necks,  as  before 
mentioned,  a  gush  of  blood  takes  place,  which  accompanies  or 
immediately  follows  the  birth  of  the  foetus.  This  hemorrhage, 
which  occurs  as  a  natural  phenomenon  at  the  time  of  parturition, 
does  not  come  from  the  uterine  vessels  proper.  It  consists  of  the 
blood  which  was  contained  in  the  placental  sinuses,  and  which  is 
expelled  from  them  owing  to  the  compression  of  the  placenta  by 
the  walls  of  the  uterus.  Since  the  whole  amount  of  blood  thus 
lost  was  previously  employed  in  the  placental  circulation,  and  since 
the  placenta  itself  is  thrown  off  at  the  same  time,  no  unpleasant 
effect  is  produced  upon  the  mother  by  such  a  hemorrhage,  because 
the  natural  •  proportion  of  blood  in  the  rest  of  the  maternal  system 
remains  the  same.  Uterine  hemorrhage  at  the  time  of  parturition, 
therefore,  becomes  injurious  only  when  it  continues  after  complete 
separation  of  the  placenta;  in  which  case  it  is  supplied  by  the 
mouths  of  the  uterine  vessels  themselves,  left  open  by  failure  of  the 
uterine  contractions.  These  vessels  are  usually  instantly  closed, 
after  separation  of  the  placenta,  by  the  contraction  of  the  muscular 
fibres  of  the  uterus.  They  pass,  as  we  have  already  mentioned,  in 
an  exceedingly  oblique  direction,  from  the  uterine  surface  to  the 
placenta ;  and  the  muscular  fibres,  which  cross  them  transversely 
above  and  below,  necessarily  constrict  them,  and  effectually  close 
their  orifices,  immediately  on  being  thrown  into  a  state  of  contraction. 

Another  very  remarkable  phenomenon,  connected  with  preg- 
nancy and  parturition  is  the  appearance  in  the  uterus  of  a  new 


634  DISCHAKGE    OF    THE    OVUM. 

mucous  membrane,  growing  underneath  the  old,  and  ready  to 
take  the  place  of  the  latter  after  its  discharge. 

If  the  internal  surface  of  the  body  of  the  uterus  be  examined 
immediately  after  parturition,  it  will  be  seen  that  at  the  spot  where 
the  placenta  was  attached,  every  trace  of  mucous  membrane  has 
disappeared.  The  muscular  fibres  of  the  uterus  are  here  perfectly 
exposed  and  bare ;  while  the  mouths  of  the  ruptured  uterine  sinuses 
are  also  visible,  with  their  thin,  ragged  edges  hanging  into  the 
cavity  of  the  uterus,  and  their  orifices  plugged  with  more  or  less 
abundant  bloody  coagula. 

Over  the  rest  of  the  uterine  surface,  the  decidua  vera  has  also 
disappeared.  Here,  however,  notwithstanding  the  loss  of  the  ori- 
ginal mucous  membrane,  the  muscular  fibres  are  not  perfectly  bare, 
but  are  covered  with  a  thin,  semi-transparent  film,  of  a  whitish  color 
and  soft  consistency.  This  film  is  an  imperfect  mucous  membrane 
of  new  formation,  which  begins  to  be  produced,  underneath  the 
old  decidua  vera,  as  early  as  the  beginning  of  the  eighth  month. 
"We  have  seen  this  new  mucous  membrane  very  distinctly  in  the 
uterus  of  a  woman  who  died  undelivered  at  the  above  period. 
The  old  mucous  membrane,  or  decidua  vera,  is  at  this  time  some- 
what opaque,  and  of  a  slightly  yellowish  color,  owing  to  a  partial 
fatty  degeneration  which  it  undergoes  in  the  latter  months  of  preg- 
nancy. It  is  easily  raised  and  separated  from  the  subjacent  parts, 
owing  to  the  atrophy  of  its  vascular  connections;  and  the  new 
mucous  membrane,  situated  beneath  it,  is  readily  distinguished  by 
its  fresh  color,  and  healthy,  transparent  aspect. 

The  mucous  membrane  of  the  cervix  uteri,  which  takes  no  part 
in  the  formation  of  the  decidua,  is  not  thrown  off  in  parturition, 
but  remains  in  its  natural  position ;  and  after  delivery  it  may  be 
seen  to  terminate  at  the  os  internum  by  an  uneven,  lacerated  edge, 
where  it  was  formerly  continuous  with  the  decidua  vera. 

Subsequently,  a  regeneration  of  the  mucous  membrane  takes  place 
over  the  whole  extent  of  the  body  of  the  uterus.  The  mucous 
membrane  of  new  formation,  which  is  already  in  existence  at  the 
time  of  delivery,  becomes  thickened  and  vascular ;  and  glandular 
tubules  are  gradually  developed  in  its  substance.  At  the  end  of 
two  months  after  delivery,  according  to  Heschl'  and  Longet,'  it  has 
entirely  regained  the  natural  structure  of  the  uterine  mucous  mem- 

'  Zeitschrift  der  K.  K.  Gesellschaft  der  Aerzte,  in  Wien,  1852. 
2  Traite  de  Physiologie.     De  la  Generation,  p.  173. 


EETROGRADE  DEVELOPMENT  OF  THE  UTERUS. 


635 


Muscular  Fibres  of  UNiMPEEr,  katkd 
Utekus;  from  a  woman  aged  4C,  dead  of  phtQiKis 
pulmonalis. 


brane.     It  unites  at  tlie  os  inter  urn,  bj  a  linear  cicatrix,  with  the 
mucous  membrane  of  the  cervix,  and  the  traces  of  its  laceration  al> 
this  spot  afterward  cease  to  be  visible.     At  the   point,  however, 
where  the  placenta  was  at- 
tached, the  regeneration  of  -  Fig.  232. 
the    mucous    membrane   is 
less  rapid;   and  a  cicatrix- 
like  spot  is  often  visible  at 
this    situation    for    several 
months  after  delivery. 

The  only  further  change, 
which  remains  to  be  de- 
scribed in  this  connection, 
is  the  fatty  degeneration 
and  reconstruction  of  the 
muscular  substance  of  the 
uterus.  This  process,  which 
is  sometimes  known  as  the 
"involution"  of  the  uterus, 
takes  place  in  the  following 
manner.  The  muscular 
fibres  of  the  unimpregnated 
uterus  are  pale,  flattened, 
spindle-shaped  bodies  (Fig. 
232)  nearly  homogeneous 
in  structure  or  very  faintly 
granular,  and  measuring 
from  3^5 

in  length,  byyo^g^  to 
of  an  inch  in  width.  During 
gestation  these  fibres  in- 
crease very  considerably  in 
size.  Their  texture  becomes 
much  more  distinctly  granu- 
lar, and  their  outlines  more 
strongly  marked.  An  oval 
nucleus  also  shows  itself  in 

the  central  part  of  each  fibre.  The  entire  walls  of  the  uterus,  at 
the  time  of  delivery,  are  composed  of  such  muscular  fibres  as 
these,  arranged  in  circular,  oblique,  and  longitudinal  bundles. 

About  the  end  of  the  first  week  after  delivery,  these  fibres  begin 


to  2^^  of  an  inch 


Muscular  Fibres  op  Human  Uterus,  ten 
days  after  parturition ;  from  a  woman  dead  of  puer- 
peral fever. 


636 


DIdCHARGE    OF    THE    OVUM. 


to  undergo  a  fatty  degeneration.  (Fig.  233.)  Their  granules  be- 
come larger  and  more  prominent,  and  very  soon  assume  the 
appearance  of  molecules  of  fat,  deposited  in  the  substance  of  the 
fibre.  The  fatty  deposit,  thus  commenced,  increases  in  abundance, 
and  the  molecules  continue  to  enlarge  until  they  become  converted 
into  fully  formed  oil-globules,  which  fill  the  interior  of  the  fibre 

more   or    less    completely, 
^'S'  234.  and  mask,  to  a  certain  ex- 

tent, its  anatomical  cha- 
racters. (Fig.  234.)  The 
universal  fatty  degenera- 
tion, thus  induced,  gives  to 
the  uterus  a  softer  consist- 
ency, and  a  pale  yellowish 
color  which  is  characteristic 
of  it  at  this  period.  The 
muscular  fibres  which  have 
become  altered  by  the  fatty 
deposit  are  afterward  gra- 
dually absorbed  and  disap- 
pear;    their    place    being 

Mfscui.ar  Fibres  of  Human  Uterus,  three      SubsCQUentlv        taken        bv 
weeks  after  parturition;  from  a  woman  dead  of  peri-  ^  r•^  n  n 

tonitis.  Other  fibres  oi  new  lorma- 

tion,  which  already  begin 
to  make  their  appearance  before  the  old  ones  have  been  completely 
destroyed.  As  this  process  goes  on,  it  results  finally  in  a  complete 
renovation  of  the  muscular  substance  of  the  uterus.  The  organ 
becomes  again  reduced  in  size,  compact  in  tissue,  and  of  a  pale 
ruddy  hue,  as  in  the  ordinary  unimpregnated  condition.  This  entire 
renewal  or  reconstruction  of  the  uterus  is  completed,  according  to 
HeschV  about  the  end  of  the  second  month  after  delivery. 


»  Op.  cit. 


EEVEL0P31ENT   OF   THE   iuMBEYO. 


6a7 


CHAPTER  XIV. 

DEVELOPMENT  OP  THE  EMBRYO— NERYOUS  SYSTEM, 
ORGANS    OF   SENSE,   SKELETON,  AND    LIMBS. 


The  first  trace  of  a  spinal  cord  in  the  embryo  consists  of  tho 
double  longitudinal  fold  or  ridge  of  tbe  blastodermic  membrane, 
whicb  shows  itself  at  an  early  period,  as  above  described,  on  each 
side  the  median  furrow.  The  two  laminse  of  which  this  is  com- 
posed, on  the  right  and  left  sides  (Fig.  235,  a,  b),  unite  with  each 
other  in  front,  forming  a  rounded  dilatation  (c), 
the  cephalic  extremity,  and  behind  at  d,  forming 
a  pointed  or  caudal  extremity.  Near  the  pos- 
terior extremitj'',  there  is  a  smaller  dilatation, 
which  marks  the  future  situation  of  the  lumbar 
enlargement  of  the  spinal  cord. 

A.a  the  laminae  above  described  grow  upward 
and  backward,  they  unite  with  each  other  upon 
the  median  line,  so  that  the  whole  is  converted 
into  a  hollow  cylindrical  cord,  terminating  ante- 
riorly by  a  bulbous  enlargement,  and  posteriorly 
by  a  pointed  enlargement;  the  central  cavity 
which  it  contains  running  continuously  through 
it,  from  front  to  rear. 

The  next  change  which  shows  itself  is  a  divi- 
sion of  the  anterior  bulbous  enlargement  into 
three  secondary  compartments  or  vesicles  (Fig. 
236),  which  are  partially  separated  from  each  other  by  transverse 
constrictions.  These  vesicles  are  known  as  the  three  cerebral  vesi- 
cles, from  which  all  the  different  parts  of  the  encephalon  are  after 
ward  to  be  developed.  The  first,  or  most  anterior  cerebral  vesicle 
is  destined  to  form  the  hemispheres;  the  second,  or  middle,  the 
tubercula  quadrigemina;  and  the  third,  or  posterior,  the  medulla 
oblongata.     All  three  vesicles  are  at  this  time  hollow,  and  their 


Formation  of  Cere- 
bko-Spfnal  Axis.— 
a,  b.  Spinal  cord.  c.  Ce- 
phalic extremity.  d. 
Caudal  extremity. 


638 


DEVELOPMENT    OF    THE    EMBRYO. 


Fig.  236. 


cavities  communicate  freelj  with  eacli  other,  through  the  interven- 
ing constrictions. 

Yer  J  soon  the  anterior  and  the  posterior  cerebral  vesicles  suffer 
a  further  division ;  the  middle  one  remain- 
ing undivided.  The  anterior  vesicle  thus 
separates  into  two  portions,  of  which  the 
first,  or  larger,  constitutes  the  hemispheres, 
while  the  second,  or  smaller,  becomes  the 
optic  thalami.  The  third  vesicle  also  sepa- 
rates into  two  portions,  of  which  the  ante- 
rior becomes  the  cerebellum,  and  the  pos- 
terior the  medulla  oblongata. 

There  are,  therefore,  at  this  time  five 
cerebral  vesicles,  all  of  whose  cavities  com- 
municate with  each  other  and  with  the 
central  cavity  of  the  spinal  cord.  The 
entire  cerebro-spinal  axis,  at  the  same  time, 
becomes  very  strongly  curved  in  an  ante- 
rior direction,  corresponding  with  the  ante- 
rior curvature  of  the  body  of  the  embryo 
(Fig.  237);  so  that  the  middle  vesicle,  or 
that  of  the  tubercula  quadrigemina,  occu- 
pies a  prominent  angle  at  the  upper  part  of 
the  encephalon,  while  the  hemispheres  and  the  medulla  oblongata 
are  situated  below  it,  anteriorly  and  posteriorly. 

At  first,  it  will  be  observed,  the  relative  size  of  the  various  parts 
of  the  encephalon  is  very  different  from  that  which 
they  afterward  attain  in  the  adult  condition.  The 
hemispheres,  for  example,  are  hardly  larger  than 
the  tubercula  quadrigemina ;  and  the  cerebellum 
is  very  much  inferior  in  size  to  the  medulla  oblon- 
gata. Soon  afterward,  the  relative  position  and  size 
of  the  parts  begin  to  alter.  The  hemispheres  and 
tubercula  quadrigemina  grow  faster  than  the  poste- 
rior portions  of  the  encephalon;  and  the  cerebellum 
becomes  doubled  backward  over  the  medulla  oblon- 
gata. (Fig.  238.)  Subsequently,  the  hemispheres 
rapidly  enlarge,  growing  upward  and  backward, 
so  as  to  cover  in  and  conceal  both  the  optic  tha- 
lami and  the  tubercula  quadrigemina  (Fig.  239);  the  cerebellum 
tending  in  the  same  way  to  grow  backward,  and  projecting  farther 


Formation  of  the  Cerebro- 
spinal Axis. — 1.  Vesicle  of 
the  hemispheres.  2.  Vesicle  of 
the  tubercula  quadrigemina.  3. 
Vesicle  of  the  medulla  oblongata. 


F(ETAL  Pia,  five- 
eighths  of  an  inch 
long,  showing  brain 
and  spinal  cord. — 1. 
Hemispheres.  2.  Tu- 
bercula quadrigemi- 
na. 3.  Cerebellum. 
4.  Medulla  oblongata. 


NEEVOUS    SYSTEM. 


639 


and  farther  over  tlie  medulla  oblongata.     The  subsequent  history 
of  the  development  of  the  encephalon  is  little  more  than  a  con- 


Fig  239. 


FcETAL  Pig,  one  and  a  quarter  inch 
long. — 1.  Hemispheres.  2.  Tubercula 
quadrigemina.  3.  Cerebellum.  4.  Me- 
dulla oblontrata. 


Head  of  Foetal  Pig,  three  and  a 
hall  incnes  lung. — \.  Hemispn^res.  3. 
Cerebellum.,    4.  Medulla  ol4ongata. 


tinuation  of  the  same  process ;  the  relative  dimensions  of  the  part& 
constantly  changing,  so  that  the  hemispheres  become,  in  the  adult 
condition  (Fig.  240),  the  largest  of  all  the  divisions  of  the  ence- 

Fig.  240. 


Beain  of   Adult  Pig. — 1.  Hemispheres.     3.  Cerebellum.     4.  Meduiia  oblongata. 

phalon,  while  the  cerebellum  is  next  in  size,  and  covers  entireW 
the  upper  portion  of  the  medulla  oblongata.  The  surfaces,  also,  of 
the  hemispheres  and  cerebellum,  which  were  at  first  smooth,  becom.e 
afterward  convoluted;  increasing,  in  this  way,  still  farther  the 
extent  of  their  nervous  matter.  In  the  human  foetus,  these  con- 
volutions begin  to  appear  about  the  beginning  of  the  fifth  month 
(Longet),  and  grow  constantly  deeper  and  more  abundant  during 
the  remainder  of  foetal  life. 

The  lateral  portions  of  the  brain  growing  at  the  same  time  more 
rapidly  than  that  which  is  situated  on  the  median  line,  they  soon 
project  on  each  side  outward  and  upward ;    and,  by  folding  over 


640  DEVELOPMENT    OF    THE    EMBRYO. 

against  each,  other  in  the  median  line,  form  the  right  and  left  hemi- 
spheres, separated  from  each  other  by  the  longitudinal  fissure. 
A  similar  process  of  growth  taking  place  in  the  spinal  cord  results 
in  the  formation  of  the  two  lateral  columns  and  the  anterior  and  pos- 
terior median  fissures  of  the  cord.  Elsewhere  the  median  fissure  is 
less  complete,  as,  for  example,  between  the  two  lateral  halves  of  the 
cerebellum,  the  two  optic  thalami  and  corpora  striata,  and  the  two 
tubercula  quadrigemina ;  but  it  exists  everywhere,  and  marks  more 
or  less  distinctly  the  division  between  the  two  sides  of  the  nervous 
centres,  produced  by  the  excessive  growth  of  their  lateral  portions. 
In  this  way  the  whole  cerebro-spinal  axis  is  converted  into  a  double 
organ,  equally  developed  upon  the  right  and  left  sides,  and  partially 
divided  by  a  longitudinal  median  fissure. 

Organs  of  Special  Sense. — The  eyes  are  formed  by  a  diverticulum 
which  grows  out  on  each  side  from  the  first  cerebral  vesicle.  This 
diverticulum  is  at  first  hollow,  its  cavity  communicating  with  that 
of  the  hemisphere.  Afterward,  the  passage  between  the  two  is  filled 
up  with  a  deposit  of  nervous  matter,  and  becomes  the  optic  nerve. 
The  globular  portion  of  the  diverticulum,  which  is  converted  into 
the  globe  of  the  eye,  has  a  very  thin  layer  of  nervous  matter  depo- 
sited upon  its  internal  surface,  which  becomes  the  retina ;  the  rest 
of  its  cavity  being  occupied  by  a  gelatinous  semi-fluid  substance, 
the  vitreous  body.  The  crystalline  lens  is  formed  in  a  distinct  fol- 
licle, which  is  an  offshoot  of  the  integument,  and  becomes  partially 
imbedded  in  the  anterior  portion  of  the  globe  of  the  eye.  The 
cornea  also  is  originally  a  part  of  the  integument,  and  remains 
partially  opaque  until  a  very  late  period  of  development.  Its  tissue 
clears  up,  however,  and  becomes  perfectly  transparent,  shortly  be- 
fore birth. 

The  iris  is  a  muscular  septum  which  is  formed  in  front  of  the 
crystalline  lens,  separating  the  anterior  and  posterior  chambers  of 
the  aqueous  humor.  Its  central  opening,  which  afterward  becomes 
the  pupil,  is  at  first  closed  by  a  vascular  membrane,  the  pupillary 
membrane,  passing  directly  across  the  axis  of  the  eye.  The  vessels 
of  this  membrane,  which  are  derived  from  those  of  the  iris,  subse- 
quently become  atrophied.  They  disappear  first  from  its  centre, 
and  afterward  recede  gradually  toward  its  circumference ;  returning 
always  upon  themselves  in  loops,  the  convexities  of  which  are  directed 
toward  the  centre  of  the  membrane.  The  pupillary  membrane  itself 
finally  becomes  atrophied  and  destroyed,  following  in  this  retro- 
grade process  the  direction  of  its  receding  bloodvessels,  viz.,  from 


SKELETON    AND    LIMBS.  641 

the  centre  toward  the  circumference.  It  has  completely  disappeared 
by  the  end  of  the  seventh  month.  (Cruveilhier.) 

The  eyelids  are  formed  by  folds  of  the  integument,  which 
gradually  project  from  above  and  below  the  situation  of  the  eye- 
ball. They  grow  so  rapidly  during  the  second  and  third  months 
that  their  free  margins  come  in  contact  and  adhere  together,  so  that 
they  cannot  be  separated  at  that  time  without  some  degree  of  vio- 
lence. They  remain  adherent  from  this  period  until  the  seventh 
month  (Gruy),  when  their  margins  separate  and  they  become  per- 
fectly free  and  movable.  In  the  carnivorous  animals,  however 
(dogs  and  cats),  the  eyelids  do  not  separate  from  each  other  until 
eight  or  ten  days  after  birth. 

The  internal  ear  is  formed  in  a  somewhat  similar  manner  with 
the  eyeball,  by  an  offshoot  from  the  third  cerebral  vesicle;  the 
passage  between  them  filling  up  by  a  deposit  of  white  substance, 
which  becomes  the  auditory  nerve.  The  tympanum  and  auditory 
meatus  are  both  offshoots  from  the  external  integument. 

Skeleton. — At  a  very  early  period  of  development  there  appears, 
as  we  have  already  described  (Chap.  YII.),  immediately  beneath  the 
cerebro-spinal  axis,  a  cylindrical  cord,  of  a  soft,  cartilaginous  con- 
sistency, termed  the  chorda  dorsalis.  It  consists  of  a  fibrous  sheath 
containing  a  mass  of  simple  cells,  closely  packed  together  and 
united  by  adhesive  material.  This  cord  is  not  intended  to  be  a 
permanent  part  of  the  skeleton,  but  is  merely  a  temporary  organ 
destined  to  disappear  as  development  proceeds. 

Immediately  around  the  chorda  dorsalis  there  are  deposited  soon 
afterward  a  number  of  cartilaginous  plates,  which  encircle  it  in  a 
series  of  rings,  corresponding  in  number  with  the  bodies  of  the  future 
vertebrae.  These  rings  increase  in  thickness  from  without  inward, 
encroaching  upon  the  substance  of  the  chorda  dorsalis,  and  finally 
taking  its  place  altogether.  The  thickened  rings,  which  have  been 
filled  up  in  this  way  and  solidified  by  cartilaginous  deposit,  become 
the  bodies  of  the  vertebrae ;  while  their  transverse  and  articulating 
processes,  with  the  laminae  and  spinous  processes,  are  formed  by 
subsequent  outgrowths  from  the  bodies  in  various  directions. 

When  the  union  of  the  dorsal  plates  upon  the  median  line  fails 
to  take  place,  the  spinal  canal  remains  open  at  that  situation,  and 
presents  the  malformation  known  as  spina  bifida.  This  malforma- 
tion may  consist  simply  in  a  fissure  of  the  spinal  canal,  more  or  less 
extensive,  in  which  case  it  may  often  be  cured,  or  may  even  close 
spontaneously ;  or  it  may  be  complicated  with  an  imperfect  deve- 
41 


642  DEVELOPMENT    OF    THE    EMBRYO. 

lopment  or  complete  absence  of  the  spinal  cord  at  the  same  spot, 
when  it  is  accompanied  of  course  hy  paralysis  of  the  lower  ex- 
tremities, and  almost  necessarily  results  in  early  death. 

The  entire  skeleton  is  at  first  cartilaginous.  The  first  points  of 
ossification  show  themselves  about  the  beginning  of  the  second 
month,  almost  simultaneously  in  the  clavicle  and  the  upper  and 
lower  jaw.  Then  come  in  the  following  order,  the  long  bones  of 
the  extremities,  the  bodies  and  processes  of  the  vertebrae,  the  bones 
of  the  head,  the  ribs,  pelvis,  scapula,  metacarpus  and  metatarsus, 
and  the  phalanges  of  the  fingers  and  toes.  The  bones  of  the  carpus, 
however,  are  all  cartilaginous  at  birth,  and  do  not  begin  to  ossif)'' 
until  a  year  afterward.  The  calcaneum  and  astragalus  begin  to 
ossify,  according  to  Cruveilhier,  during  the  latter  periods  of  foetal 
life,  but  the  remainder  of  the  tarsus  is  cartilaginous  at  birth.  The 
lower  extremity  of  the  femur  begins  to  ossify,  according  to  the 
same  author,  during  the  latter  half  of  the  ninth  month.  The  pisiform 
bone  of  the  carpus  is  said  to  commence  its  ossification  later  than 
any  other  bone  in  the  skeleton,  viz.,  at  from  twelve  to  fifteen  years 
after  birth.  Nearly  all  the  bones  ossify  from  several  distinct  points ; 
the  ossification  spreading  as  the  cartilage  itself  increases  in  size, 
and  the  various  bony  pieces,  thus  produced,  uniting  with  each  other 
at  a  later  period,  usually  some  time  after  birth. 

The  limbs  appear  by  a  kind  of  budding  process,  as  offshoots  of 
the  external  layer  of  the  blastodermic  membrane.  They  are  at 
first  mere  rounded  elevations,  without  any  separation  between  the 
fingers  and  toes,  or  any  distinction  between  the  different  articula- 
tions. Subsequently  the  free  extremity  of  each  limb  becomes  di- 
vided into  the  phalanges  of  the  fingers  or  toes ;  and  afterward  the 
articulations  of  the  wrist  and  ankle,  knee  and  elbow,  shoulder  and 
hip,  appear  successively  from  below  upward. 

The  posterior  extremities,  in  the  human  subject,  are  less  rapid  in 
their  development  than  the  anterior.  Throughout  the  term  of 
foetal  life,  indeed,  the  anterior  parts  of  the  body  are  generally  more 
voluminous  than  the  posterior.  The  younger  the  embryo,  the  larger 
are  the  head  and  upper  extremities  in  proportion  to  the  rest  of  the 
body.  The  lower  limbs  and  the  pelvis,  more  particularly,  are  very 
slightly  developed  in  the  early  periods  of  growth,  as  compared  with 
the  spinal  column,  to  which  they  are  attached.  The  inferior  ex- 
tremity of  the  spinal  column,  formed  by  the  sacrum  and  coccyx, 
projects  at  this  time  considerably  beyond  the  pelvis,  forming  a  tail, 
like  that  of  the  lower  animals,  which  is  curled  forward  toward  the 


SKELETON    AND    LIMBS.  643 

abdomen,  and  terminates  in  a  pointed  extremity.  Subsequently  the 
pelvis  and  the  muscular  parts  seated  upon  it  grow  so  much  faster 
than  the  sacrum  and  coccyx,  that  the  latter  become  concealed 
under  the  adjoining  soft  parts,  and  the  rudimentary  tail  accord- 
ingly disappears. 

The  integument  of  the  embryo  is  at  first  thin,  vascular,  and  ex- 
ceedingly transparent.  It  afterward  becomes  thicker,  more  opaque, 
and  whitish  in  color;  though  even  at  birth  it  is  more  vascular  than 
in  the  adult  condition,  and  the  ruddy  color  of  its  abundant  capil- 
lary vessels  is  then  very  strongly  marked.  The  hairs  begin  to 
appear  about  the  middle  of  intra-uterine  life ;  showing  themselves 
first  upon  the  eyebrows,  and  afterward  upon  the  scalp,  trunk  and 
extremities.  The  nails  are  in  process  of  formation  from  the  third 
to  the  fifth  month ;  and,  according  to  Kolliker,  are  still  covered 
with  a  layer  of  epidermis  until  after  the  latter  period.  The  seba- 
ceous matter  of  the  cutaneous  glandules  accumulates  upon  the  skin 
after  the  sixth  month,  and  forms  a  whitish,  semisolid,  oleaginous 
layer,  termed  the  vernix  caseosa,  which  is  most  abundant  in  the 
flexures  of  the  joints,  between  the  folds  of  the  integument,  behind 
the  ears  and  upon  the  scalp. 

The  cells  of  the  epidermis  are  repeatedly  exfoliated  after  the  first 
five  months  of  foetal  life  (Kolliker),  and  replaced  by  others  of  new 
formation  and  of  larger  size.  These  exfoliated  epidermic  cells  are 
found  mingled  with  the  sebaceous  matter  of  the  vernix  caseosa  in 
great  abundance.  This  semi-oleaginous  layer,  with  which  the  in- 
tegument is  covered,  becomes  exceedingly  useful  in  the  process  of 
parturition,  by  lubricating  the  surface  of  the  body,  and  allowing  ii 
to  pass  easily  through  the  generative  passages. 


64-i  DEVELOPMENT    OF    THE    ALIMENTARY    CANAL 


CHAPTER   XV. 

DEYELOPMENT  OF  THE  ALIMENTARY  CANAL 
AND  ITS  APPENDAGES. 

We  have  already  seen,  in  a  preceding  chapter,  that  the  intestinal 
canal  is  formed  by  the  internal  layer  of  the  blastodermic  membrane, 
which  curves  forward  on  each  side,  and  is  thus  converted  into  a 
nearly  straight  cylindrical  tube,  terminating  at  each  extremity  in 
a  rounded  cul-de-sac,  and  inclosed  by  the  external  layer  of  the 
blastodermic  membrane.  The  abdominal  walls,  however,  do  not 
unite  with  each  other  upon  the  median  line  until  long  after  the 
formation  of  the  intestinal  canal ;  so  that,  during  a  certain  period, 
the  abdomen  of  the  embryo  is  widely  open  in  front,  presenting  a 
long  oval  excavation,  in  which  the  nearly  straight,  intestinal  tube 
is  to  be  seen,  running  from  its  anterior  to  its  posterior  extremity. 

The  formation  of  the  stomach  takes  place  in  the  following  man- 
ner :  The  alimentary  canal,  originally  straight,  soon  presents  two 
lateral  curvatures  at  the  upper  part  of  the  abdomen ;  the  first  to 
the  left,  the  second  to  the  right.  The  first  of  these  curvatures 
becomes  expanded  into  a  wide  sac,  projecting  laterally  from  the 
median  line  into  the  left  hypochondrium,  forming  the  great  pouch 
of  the  stomach.  The  second  curvature,  directed  to  the  right,  marks 
the  boundary  between  the  stomach  and  the  duodenum ;  and  the 
tube  at  that  point  becoming  constricted  and  furnished  with  a  circular 
layer  of  muscular  fibres,  is  converted  into  the  pylorus.  Immedi- 
ately below  the  pylorus,  the  duodenum  again  turns  to  the  left ;  and 
these  curvatures,  increasing  in  number  and  complexity,  form  the 
convolutions  of  the  small  intestine.  The  large  intestine  forms  a 
spiral  curvature ;  ascending  on  the  right  side,  then  crossing  over 
to  the  left  as  the  transverse  colon,  and  again  descending  on  the  left 
side,  to  terminate  by  the  sigmoid  flexure  in  the  rectum. 

The  curvatures  of  the  intestinal  canal  take  place,  however,  in  an 
antero-posterior,  as  well  as  in  a  lateral  direction,  and  may  be  best 
studied  in  a  profile  view,  as  in  Fig.  241.     The  abdominal  walls  are 


AND    ITS    APPENDAGES.  645 

here  still  imperfectly  closed,  leaving  a  wide  opening  at  a,  h,  where 
the  integument  of  the  foetus  becomes  continuous  with  the  com- 
mencement of  the  amniotic  membrane.     The  intestine  makes  at 

Fig.  241. 


Formation  of  Aliment ARY  Canal. — a,  h.  Commencement  of  amnion,  c,  c.  Intestine,  d 
Pharynx,  e.  Urinary  bladder.  /  Allantois.  g.  Umbilical  vesicle,  x.  Dotted  line,  showing  the 
place  of  formation  of  the  oesophagus. 

first  a  single  angular  turn  forward,  and  opposite  the  most  promi- 
nent  portion  of  this  angle  is  to  be  seen  the  obliterated  duct,  which 
forms  the  stem  of  the  umbilical  vesicle,  {g)  A  short  distance  below 
this  point  the  intestine  subsequently  enlarges  in  its  calibre,  and  the 
situation  of  this  enlargement  marks  the  commencement  of  the 
colon.  The  two  portions  of  the  mtestinC;  after  this  period,  become 
widely  different  from  each  other.  The  upper  portion,  which  is  the 
small  intestine,  grows  mostly  in  the  direction  of  its  length,  and 
becomes  a  very  long,  narrow,  and  convoluted  tube ;  while  the  lower 
portion,  which  is  the  large  intestine,  increases  rapidly  in  diameter, 
but  elongates  less  than  the  former. 

At  the  point  of  junction  of  the  small  and  large  intestines,  a  late- 
ral bulging  or  diverticulum  of  the  latter  shows  itself,  and  increases 
in  extent,  until  the  ileum  seems  at  last  to  be  inserted  obliquely  into 
the  side  of  the  colon.  This  diverticulum  of  the  colon  is  at  first 
uniformly  tapering  or  conical  in  shape ;  but  afterward  that  portion 
which  forms  its'free  extremity,  becomes  narrow  and  elongated,  and 
is  slightly  twisted  upon  itself  in  a  spiral  direction,  forming  the 
appendix  vermiformis;  while  the  remaining  portion,  which  is  con- 
tinuous with  the  intestine,  becomes  exceedingly  enlarged,  and  forms 
the  caput  coli. 

The  caput  coli  and  the  appendix  are  at  first  situated  near  the 


646 


DEVELOPMENT    OF    THE    ALIMENTARY    CANAL 


Fig.  242. 


umbilicus ;  but  between  the  fourth  and  fifth  months  (Cruveilhier) 
their  position  is  altered,  and  they  then  become  fixed  in  the  right 
iliac  region.  During  the  first  six  months,  the  internal  surface  of 
the  small  intestine  is  smooth.  At  the  seventh  month,  according  to 
Cruveilhier,  the  valvules  conniventes  begin  to  appear,  after  which 
they  increase  in  size  till  birth.  The  division  of  the  colon  into 
sacculi  by  longitudinal  and  transverse  bands,  is  also  an  appearance 
which  presents  itself  only  during  the  last  half  of  foetal  life.  Pre- 
vious to  that  time,  the  colon  is  smooth  and  cylindrical  in  figure, 
like  the  small  intestine. 

After  the  small  intestine  is  once  formed,  it  increases  very  rapidly 
in  length.     It  grows,  indeed,  at  this  time,  faster  than  the  walls  of 

the  abdomen;  so  that  it  can  no  longer 
be  contained  in  the  abdominal  cavity, 
but  protrudes,  under  the  form  of  an  in- 
testinal loop,  or  hernia,  from  the  umbili- 
cal opening.  (Fig.  242.)  In  the  human 
embryo,  this  protrusion  of  the  intestine 
can  be  readily  seen  during  the  latter  part 
of  the  second  month.  At  a  subsequent 
period,  however,  the  walls  of  the  abdo- 
men grow  more  rapidly  than  the  intes- 
tine. They  accordingly  gradually  en- 
velop the  hernial  protrusion,  and  at  last 
inclose  it  again  in  the  cavity  of  the  ab- 
domen. 

Owing  to  an  imperfect  development 
of  the  abdominal  walls,  and  an  imperfect 
closure  of  the  umbilicus,  this  intestinal 
protrusion,  which  is  normal  during  the  early  stages  of  foetal  life, 
sometimes  remains  at  birth,  and  we  then  have  a  congenital  umbilical 
hernia.  As  the  parts  at  that  time,  however,  have  a  natural  tendency 
to  cicatrize  and  unite  with  each  other,  simple  pressure  is  generally 
effectual,  in  such  cases,  in  retaining  the  hernia  within  the  abdomen, 
and  in  producing  at  last  a  complete  cure. 

Urinary  Bladder,  Urethra,  ko. — It  will  be  recollected  that  very 
soon  after  the  formation  of  the  intestine,  a  vascular  outgrowth  takes 
place  from  its  posterior  portion,  which  gradually  protrudes  from  the 
open  walls  of  the  abdomen  in  front,  until  it  comes  in  contact  with 
the  external  investing  membrane  of  the  egg,  and  forms,  by  its  con- 
tinued growth  and  expansion,  the  allantois.  (Fig.  241,/.)     It  is  at 


F(ETAL  Pio,  showing  loop 
of  intestine,  forming  umbilical 
hernia ;  from  a  specimen  in  the 
author's  possession.  From  the 
convexity  of  the  loop  a  thin  filament 
is  seen  passing  to  the  umbilical 
vesicle,  which  is  here  flattened  into 
a  leaf-like  form. 


AND    ITS    APPENDAGES.  647 

first,  as  we  have  shown  above,  a  hollow  sac ;  but,  as  it  spreads  out 
over  the  surface  of  the  investing  membrane  of  the  egg,  its  two 
opposite  walls  adhere  to  each  other,  so  that  its  cavity  is  obliterated 
at  this  situation,  and  it  is  thus  converted  into  a  single  vascular 
membrane,  the  chorion.  This  obliteration  of  the  cavity  of  the 
allantois  commences  at  its  external  portion,  and  gradually  extends 
inward  toward  the  point  of  its  emergence  from  the  abdomen.  The 
hollow  tube,  or  duct,  which  connects  the  cavity  of  the  allantois  with 
the  posterior  part  of  the  intestine,  is  accordingly  converted,  as  the 
process  of  obliteration  proceeds,  into  a  solid,  rounded  cord.  This 
cord  is  termed  the  urachus. 

After  the  walls  of  the  abdomen  have  come  in  contact,  and  united 
with  each  other  at  the  umbilicus,  that  portion  of  the  above  duct 
which  is  left  outside  the  abdominal  cavity,  forms  a  part  of  the  um- 
bilical cord,  and  r^lmains  connected  with  the  umbilical  arteries  and 
vein.  That  portion,  on  the  contrary,  which  is  included  in  the  ab- 
domen, does  not  close  completely,  but  remains  as  a  pointed  fusiform 
sac,  terminating  near  the  umbilicus  in  the  solid  cord  of  the  urachus, 
and  still  communicating  at  its  base  with  the  lower  extremity  of  the 
intestinal  canal.  This  fusiform  sac  (Fig.  241,  e),  becomes  the  uri- 
nary bladder ;  and  in  the  foetus  at  term,  the  bladder  is  still  conical 
in  form,  its  pointed  extremity  being  attached,  by  means  of  the  ura- 
chus, to  the  internal  surface  of  the  abdominal  walls  at  the  situation 
of  the  umbilicus.  Afterward,  the  bladder  loses  this  conical  form, 
and  its  fundus  in  the  adult  becomes  rounded  and  bulging. 

The  urinary  bladder,  as  it  appears  from  the  above  description,  at 
first  communicates  freely  with  the  intestinal  cavity.  The  intestine, 
in  fact,  terminates,  at  this  time,  in  a  wide  passage,  or  cloaca,  at  its 
lower  extremity,  which  serves  as  a  common  outlet  for  the  urinary 
and  intestinal  passages.  Subsequently,  however,  a  horizontal  par- 
tition makes  its  appearance  just  above  the  point  of  junction  between 
the  bladder  and  rectum,  and  grows  downward  and  forward  in  such 
a  manner  as  to  divide  the  above-mentioned  cloaca  into  two  parallel 
and  unequal  passages.  The  anterior  or  smaller  of  these  passages 
becomes  the  urethra,  the  posterior  or  larger  becomes  the  rectum ; 
and  the  lower  edge  of  the  septum  between  them  becomes  finally 
united  with  the  skin,  forming,  at  its  most  superficial  part,  a  tole 
rably  wide  band  of  integument,  the  perineum,  which  interveners 
between  the  anus  and  the  external  portion  of  the  urethra. 

The  contents  of  the  intestine,  which  accumulate  during  foetal  life, 
vary  in  different  parts  of  the  alimentary  canal.     In  the  small  intes- 


648  DEVELOPMENT    OF    THE    ALIMENTARY    CANAL 

tine  thej  are  semifluid,  or  gelatinous  in  consistency,  of  a  light 
yellowish  or  grayish-white  color  in  the  duodenum,  becoming  yellow, 
reddish-brown  and  greenish -brown  below.  In  the  large  intestine 
they  are  of  a  dark  greenish  hue,  and  pasty  in  consistency ;  and  the 
contents  of  this  portion  of  the  alimentary  canal  have  received  the 
name  of  meconium,  from  their  resemblance  to  inspissated  poppy- 
juice.  The  meconium  contains  a  large  quantity  of  fat,  as  well  as 
various  insoluble  substances,  probably  the  residue  of  epithelial  and 
mucous  accumulations.  It  does  not  contain,  however,  any  trace  of 
the  biliary  substances  (tauro-cholates  and  glyko-cholates)  when  care- 
fully examined  by  Pettenkofer's  test ;  and  cannot  therefore  properly 
be  regarded,  as  is  sometimes  incorrectly  asserted,  as  resulting  from 
the  accumulation  of  bile.  In  the  contents  of  the  small  intestine,  on 
the  contrary,  traces  of  bile  may  be  found,  according  to  Lehmann,^ 
so  early  as  between  the  fifth  and  sixth  montfes.  We  have  also 
found  distinct  traces  of  bile  in  the  small  intestine  at  birth,  but  it  is 
even  then  in  extremely  small  quantity,  and  is  sometimes  altogether 
absent. 

The  meconium,  therefore,  and  the  intestinal  contents  generally, 
are  not  composed  principally,  or  even  to  any  appreciable  extent,  of 
the  secretions  of  the  liver.  They  appear  rather  to  be  produced  by 
the  mucous  membrane  of  the  intestine  itself.  Even  their  yellowish 
and  greenish  color  does  not  depend  on  the  presence  of  bile,  since 
the  yellow  color  first  shows  itself,  in  very  young  foetuses,  about 
the  middle  of  the  small  intestine,  and  not  at  its  upper  extremity. 
The  material  which  accumulates  afterward  appears  to  extend  from 
this  point  upward  and  downward,  gradually  filling  the  intestine, 
and  becoming,  in  the  ileum  and  large  intestine,  darker  and  more 
pasty  as  gestation  advances. 

It  is  a  singular  fact,  perhaps  of  some  importance  in  this  connec- 
tion, that  the  amniotic  fluid,  during  the  latter  half  of  foetal  life, 
finds  its  way,  in  greater  or  less  abundance,  into  the  stomach,  and 
through  that  into  the  intestinal  canal.  Small  cheesy-looking  masses 
may  sometimes  be  found  at  birth  in  the  fluid  contained  in  the 
stomach,  which  are  seen  on  microscopic  examination  to  be  no  other 
than  portions  of  the  vernix  caseosa  exfoliated  from  the  skin  into 
the  amniotic  cavity,  and  afterward  swallowed.  According  to  Kol- 
liker,^  the  soft  downy  hairs  of  the  foetus,  exfoliated  from  the  skin, 

'  Physiological  Chemistry,  Philadelphia  edition,  vol.  i.  p.  532. 
2  Gewebelehre.     Leipzig,  1852,  p.  139. 


AN-D    ITS    APPENDAGES.  649 

are  often  swallowed  in  the  same  way,  and  may  be  found  in  the 
meconium. 

The  gastric  juice  is  not  secreted  before  birth ;  the  contents  of  the 
stomach  being  generally  in  small  quantity,  clear,  nearly  colorless, 
and  neutral  or  alkaline  in  reaction. 

The  liver  is  developed  at  a  very  early  period.  Its  size  in  pro- 
portion to  that  of  the  entire  body  is,  in  fact,  very  much  greater  in 
the  early  months  than  at  birth  or  in  the  adult  condition.  In  the 
foetal  pig  we  have  found  the  relative  size  of  the  liver  greatest 
within  the  first  month,  when  it  amounts  to  very  nearly  12  per  cent, 
of  the  entire  weight  of  the  body.  Afterward,  as  it  grows  less  rapidly 
than  other  parts,  its  relative  weight  diminishes  successively  to  10 
per  cent,  and  6  per  cent. ;  and  is  reduced  before  birth  to  3  or  4  per 
cent.  In  the  human  subject,  also,  the  weight  of  the  liver  at  birth 
is  between  3  and  4  per  cent,  of  that  of  the  entire  body. 

The  secretion  of  hile  takes  place,  as  we  have  intimated  above, 
during  foetal  life,  in  a  very  scanty  manner.  We  have  found  it,  in 
minute  quantity,  in  the  gall-bladder,  as  well  as  in  the  small  intes- 
tine at  birth ;  but  it  does  not  probably  take  any  active  part  in  the 
nutritive  or  other  functions  of  the  foetus  before  that  period. 

The  glycogenic  function  of  the  liver  commences  during  foetal  life, 
and  at  birth  the  tissue  of  the  organ  is  abundantly  saccharine.  It  is 
remarkable,  however,  that  in  the  early  periods  of  gestation  sugar  is 
produced  in  the  foetus  from  other  sources  than  the  liver.  In  very 
young  foetuses  of  the  pig,  for  example,  both  the  allantoic  and 
amniotic  fluids  are  saccharine,  a  considerable  time  before  any  sugar 
makes  its  appearance  in  the  tissue  of  the  liver.  Even  the  urine,  in 
half-grown  foetal  pigs,  contains  an  appreciable  quantity  of  sugar, 
and  the  young  animal  is  therefore,  at  this  period,  in  a  diabetic  con- 
dition. This  sugar,  however,  disappears  from  the  urine  before  birth, 
and  also  from  the  amniotic  fluid,  as  has  been  ascertained  by  M.  Ber- 
nard ;'  while  the  liver  begins  to  produce  a  saccharine  substance,  and 
to  exercise  the  glycogenic  function,  which  it  continues  after  birth. 

Development  of  the  Pharynx,  (Esophagus,  dtc. — We  have  already 
seen  that  the  intestinal  canal  consists  at  first  of  a  cylindrical  tube 
terminated  at  each  extremity  of  the  abdominal  cavity  by  a  rounded 
cul-de-sac  (Fig.  241,  c,  c) ;  and  that  the  openings  of  the  mouth  and 
anus  are  subsequently  formed  by  perforations  which  take  place 
through  the  integument  and  the  intervening  tissues,  and  so  estab- 

•  Le  ons  de  Phyaiologie  Experiraentale,  Paris,  1855,  p,  398- 


650  DEVELOPMENT    OF    THE    ALIMENTARY    CANAL 

lish  a  communication  with,  the  intestinal  tube.  The  formation  of 
the  anterior  perforation,  and  its  appendages,  takes  place  in  the  fol- 
lowing manner : — 

After  the  early  development  of  the  intestinal  tube  in  the  mode 
above  described,  the  head  increases  in  size  out  of  all  proportion  to 
the  remainder  of  the  foetus,  projecting  as  a  large  rounded  mass  from 
the  anterior  extremity  of  the  body,  and  containing  the  brain  and  the 
organs  of  special  sense.  This  portion  soon  bends  over  toward  the 
abdomen,  in  consequence  of  the  increasing  curvature  of  the  whole 
body  which  takes  place  at  this  time.  In  the  interior  of  this 
cephalic  mass  there  is  now  formed  a  large  cavity  (Fig.  241,  d),  by 
the  melting  down  and  liquefaction  of  a  portion  of  its  substance. 
This  cavity  is  the  pharynx.  It  corresponds  by  its  anterior  extre- 
mity to  the  future  situation  of  the  mouth ;  and  by  its  posterior 
portion  to  the  upper  end  of  the  intestinal  canal,  the  future  situation 
of  the  stomach.  It  is  still,  however,  closed  on  all  sides,  and  does 
not  as  yet  communicate  either  with  the  exterior  or  with  the  cavity 
of  the  stomach.  There  is,  accordingly,  at  this  time,  no  thorax 
whatever ;  but  the  stomacb  lies  at  the  upper  extremity  of  the  abdo- 
men, immediately  beneath  the  lower  extremity  of  the  pharynx,  from 
which  it  is  separated  by  a  wall  of  intervening  tissue. 

Subsequently,  a  perforation  takes  place  between  the  adjacent 
extremities  of  the  pharynx  and  stomach,  by  a  short  narrow  tube, 
the  situation  of  which  is  marked  by  the  dotted  lines  x,  in  Fig.  241. 
This  tube  afterward  lengthens  by  the  rapid  growth  of  that  portion 
of  the  body  in  which  it  is  contained,  and  becomes  the  oesophagus. 
Neither  the  pharynx  nor  oesophagus,  therefore,  are,  properly  speak- 
ing, parts  of  the  intestinal  canal,  formed  from  the  internal  layer  of 
the  blastodermic  membrane ;  but  are,  on  the  contrary,  formations 
of  the  external  layer,  from  which  the  entire  cephalic  mass  is  pro- 
duced. The  lining  membrane  of  the  pharynx  and  oesophagus  is  to 
be  regarded,  also,  for  the  same  reason,  as  rather  a  continuation  of 
the  integument  than  of  the  intestinal  mucous  membrane ;  and  even 
in  the  adult,  the  thick,  whitish,  and  opaque  pavement  epithelium 
of  the  oesophagus  may  be  seen  to  terminate  abruptly,  by  a  well- 
defined  line  of  demarkation,  at  the  cardiac  orifice  of  the  stomach ; 
beyond  which,  throughout  the  remainder  of  the  alimentary  canal, 
the  epithelium  is  of  the  columnar  variety,  and  easily  distinguish- 
able by  its  soft,  ruddy,  and  transparent  appearance. 

As  the  oesophagus  lengthens,  the  lungs  are  developed  on  each 
side  of  it  by  a  protrusion  from  the  pharynx  which  extends  and 


AND    ITS    APPENDAGES.  651 

becomes  repeatedly  subdivided,  forming  the  bronchial  tubes  and 
their  ramifications.  At  first,  the  lungs  project  into  the  upper 
part  of  the  abdominal  cavity ;  for  there  is  still  no  distinction  be- 
tween the  chest  and  abdomen.  Afterward,  a  horizontal  partition 
begins  to  form  on  each  side,  at  the  level  of  the  base  of  the  lungs, 
which  gradually  closes  together  at  a  central  point,  so  as  to  form 
the  diaphragm,  and  finally  shuts  off  altogether  the  cavity  of 
the  chest  from  that  of  the  abdomen.  Before  the  closure  of  the 
diaphragm,  thus  formed,  is  complete,  a  circular  opening  exists  on 
each  side  the  median  line,  by  which  the  peritoneal  and  pleural 
cavities  communicate  with  each  other.  In  some  instances  the  de- 
velopment of  the  diaphragm  is  arrested  at  this  point,  either  on  one 
side  or  the  other,  and  the  opening  accordingly  remains  permanent. 
The  abdominal  organs  then  partially  protrude  into  the  cavity  of 
the  chest  on  that  side,  forming  congenital  diaphragmatic  hernia. 
The  lung  on  the  affected  side  also  usually  remains  in  a  state  of 
imperfect  development.  Diaphragmatic  hernia  of  this  character  is 
more  frequently  found  upon  the  left  side  than  upon  the  right.  It 
may  sometimes  continue  until  adult  life  without  causing  any  seri- 
ous inconvenience. 

The  heart  is  formed,  at  a  very  early  period,  directly  in  front  of 
the  situation  of  the  oesophagus.  Its  size  soon  becomes  very  large 
in  proportion  to  the  rest  of  the  body ;  so  that  it  protrudes  beyond 
the  level  of  the  thoracic  parietes,  covered  only  by  the  pericardium. 
Subsequently,  the  walls  of  the  thorax,  becoming  more  rapidly 
developed,  grow  over  it  and  inclose  it.  In  certain  instances,  how- 
ever, they  fail  to  do  so,  and  the  heart  then  remains  partially  or 
completely  uncovered,  in  front  of  the  chest,  presenting  the  condition 
known  as  ectopia  cordis.     This  malformation  is  necessarily  latal. 

Development  of  the  Face. — While  the  lower  extremity  of  the 
pharynx  communicates  with  the  cavity  of  the  stomach,  as  above 
described,  its  upper  extremity  also  becomes  perforated  in  a  similar 
manner,  and  establishes  a  communication  with  the  exterior.  This 
perforation  is  at  first  wide  and  gaping.  It  afterward  becomes 
divided  into  the  mouth  and  nasal  passages ;  and  the  different  parts 
of  the  face  are  formed  round  it  in  the  following  manner : — 

From  the  sides  of  the  cephalic  mass  five  buds  or  processes  shoot 
out,  and  grow  toward  each  other,  so  as  to  approach  the  centre  of 
the  oral  orifice  above  mentioned.  (Fig.  243.)  One  of  them  grows 
directly  downward  from  the  frontal  region  (i),  and  is  called  the 
frontal  or  intermaxillary  process,  because  it  afterward  contains  in 


652 


DEVELOPMENT    OF    THE    ALIMENTARY    CANAL 


Fig.  243. 


Head  of  Human  Embryo, 
at  about  the  twentieth  day.  After 
Longet ;  from  a  specimen  ia  the 
collection  of  M.  Coste. — 1.  Frontal 
or  intermaxillary  process.  2.  Pro- 
cess of  superior  maxilla.  3.  Pro- 
cess of  inferior  maxilla. 


its  lower  extremity  the  intermaxillary  bones,  in  whicli  the  incisor 
teeth  of  the  upper  jaw  are  inserted.  The  next  process  (2)  origin- 
ates from  the  side  of  the  opening,  and,  advancing  toward  the  median 

line,  forms,  with  its  fellow  of  the  opposite 
side,  the  superior  maxilla.  The  processes 
of  the  remaining  pair  (3)  also  grow  from 
the  side,  and  form,  by  their  subsequent 
union  upon  the  median  line,  the  inferior 
maxilla.  The  inferior  maxillary  bone  is 
finally  consolidated,  in  man,  into  a  single 
piece,  but  remains  permanently  divided, 
in  the  lower  animals,  by  a  suture  upon  the 
median  line. 

As  the  frontal  process  grows  from  above 
downward,  it  becomes  double  at  its  lower 
extremity,  and  at  the  same  time  two  off- 
shoots show  themselves  upon  its  sides, 
which  curl  round  and  inclose  two  circular 
orifices,  the  opening  of  the  anterior  nares ;  the  offshoots  themselves 
becoming  the  aire  nasi.  (Fig,  244.)  The  mouth  at  this  period  is 
very  widely  open,  owing  to  the  imperfect  development  of  the  upper 

and   lower  jaw,  and   the  incomplete 
formation  of  the  lips  and  cheeks. 

The  processes  of  the  superior  max- 
illa continue  their  growth,  but  less 
rapidly  than  those  of  the  inferior ;  so 
that  the  two  sides  of  the  lower  jaw 
are  already  consolidated  with  each 
other,  while  those  of  the  upper  jaw 
are  still  separate. 

As  the  processes  of  the  superior 
maxilla  continue  to  enlarge,  they  also 
tend  to  unite  with  each  other  on  the 
median  line,  but  are  prevented  from 
doing  so  by  the  intermaxillary  pro- 
cesses which  grow  down  between  them.  They  then  unite  with  the 
intermaxillary  processes,  which  have  at  the  same  time  united  with 
each  other,  and  the  upper  jaw  and  lip  are  thus  completed.  (Fig. 
245.)  The  external  edge  of  the  ala  nasi  also  adheres  to  the  superior 
maxillary  process  and  unites  with  it,  leaving  only  a  curved  crease 


Fig.  244. 


Head  of  Human  Embryo  at  aliout 
the  sixth  week.  From  a  specimen  iu  ilie 
author's  possession. 


AND    ITS    APPENDAGES. 


Fig.  245. 


Head  of  Human  Embryo,  ab(.ut 
the  end  of  the  second  month. — From  a 
specimen  in  the  author's  possession. 


or  furrow,  as  a  sort  of  cicatrix,  to  mark  the  line  of  union  between 
them.  . 

Sometimes  the  superior  maxillary  and  the  intermaxillary  pro- 
cesses fail  to  unite  with  each  other ;  and  we  then  have  the  mal- 
formation known  as  hare-lip.  The 
fissure  of  hare-lip,  consequently,  as  a 
general  rule,  is  not  situated  exactly  in 
the  median  line,  but  a  little  to  one  side 
of  it,  on  the  external  edge  of  the  inter- 
maxillary process.  Occasionally,  the 
same  deficiency  exists  on  both  sides, 
producing  "  double  hare-lip ;"  in  which 
case,  if  the  fissures  extend  through 
the  bony  structures,  the  central  piece 
of  the  superior  maxilla,  which  is  de- 
tached from  the  remainder,  contains 
the  four  npper  incisor  teeth,  and  cor- 
responds with  the  intermaxillary  bone 

of  the  lower  animals.  In  some  rare  instances  the  fissure  of  hare- 
lip is  situated  in  the  median  line,  the  two  intermaxillary  bones 
never  having  united  with  each  other.  A  case  of  this  kind  has 
been  observed  by  Prof.  Jeffries  Wyman.^ 

The  eyes  at  an  early  period  are  situated  upon  the  sides  of  the 
head,  so  that  they  cannot  be  seen  in  an  anterior  view.  (Fig,  243.) 
As  development  proceeds,  they  come  to  be  situated  farther  forward 
(Fig.  244),  their  axes  being  divergent  and  directed  obliquely  for- 
ward and  outward.  At  a  later  period  still  they  are  placed  on  the 
anterior  plane  of  the  face  (Fig.  245),  and  have  their  axes  nearly 
parallel  and  looking  directly  forward.  This  change  in  the  situa- 
tion of  the  eyes  is  effected  by  the  more  rapid  growth  of  the  pos- 
terior and  lateral  parts  of  the  head,  which  enlarge  in  such  a  manner 
as  to  alter  the  relative  position  of  the  parts  seated  in  front  of  them. 

The  palate  is  formed  by  a  septum  between  the  mouth  and  nares, 
which  arises  on  each  side  as  a  horizontal  plate  or  offshoot  from  the 
superior  maxilla.  These  two  plates  afterward  unite  with  each 
other  upon  the  median  line,  forming  a  complete  partition  between 
the  oral  and  nasal  cavities.  The  right  and  left  nasal  passages  are 
also  separated  from  each  other  by  a  vertical  plate  (vomer),  which 
grows  from  above  downward  and  fuses  with  the  palatal  plates  be- 


Transactions  Boston  Society  for  Medical  Improvement,  March  !)th,  1863. 


654      DEVELOPMENT    OF    THE    ALIMENTARY    CANAL,   ETC. 

low.  Fissure  of  the  palate  is  caused  by  a  deficiency,  more  or  less 
complete,  of  one  of  the  horizontal  maxillary  plates.  It  is  accord- 
ingly situated  a  little  on  one  side  of  the  median  line,  and  is  fre- 
quently associated  with  hare-lip  and  fissure  of  the  upper  jaw.  The 
fissures  of  the  palate  and  of  the  lip  are  very  often  continuous  with 
each  other. 

The  anterior  and  posterior  pillars  of  the  fauces  are  incomplete 
vertical  partitions,"  which  grow  from  the  sides  of  the  oral  cavity, 
and  tend  to  separate,  by  a  slight  constriction,  the  cavity  of  the 
mouth  from  that  of  the  pharynx. 

When  all  the  above  changes  are  accomplished,  the  pharynx, 
oesophagus,  mouth,  nares,  and  fauces,  with  their  various  projections 
and  divisions,  have  been  successively  formed ;  and  the  development 
of  the  upper  part  of  the  alimentary  canal  is  then  complete. 


DEVJiLOPMENT    OF   THE    KIDNEYS. 


655 


CHAPTER   XVI. 

DEVELOPMENT  OF  THE  KIDNEYS,  WOLFFIAN 
BODIES,  AND  INTERNAL  ORGANS  OF  GENE- 
RATION. 


Fig.  246. 


The  first  trace  of  a  urinary  apparatus  in  the  embryo,  consists  of 
two  long,  fusiform  bodies,  which  make  their  appearance  in  the  ab- 
domen at  a  very  early  period,  situated  on  each  side  the  spinal 
column.  These  are  known  by  the  name  of  the  Wolffian  todies. 
They  are  fully  formed  in  the  human  subject,  toward  the  end  of  the 
first  month  (Coste),  at  which  time  they  are  the  largest  organs  in  the 
cavity  of  the  abdomen,  extending  from  just  below  the  heart,  nearly 
to  the  posterior  extremity  of  the  body.  In  the  foetal  pig,  when  a 
little  over  half  an  inch  in  length  (Fig.  246),  the  Wolffian  bodies  are 
rounded  and  kidney-shaped,  and  occupy  a 
very  large  part  of  the  abdominal  cavity. 
Their  importance  may  be  estimated  from  the 
fact  that  their  weight  at  this  time  is  equal  to 
a  little  over  -g'.j  of  that  of  the  entire  body — a 
proportion  which  is  seven  or  eight  times  as 
large  as  that  of  the  kidneys  in  the  adult 
condition.  There  are,  indeed,  at  this  period 
only  three  organs  perceptible  in  the  abdo- 
men, viz.,  the  liver,  which  has  begun  to  be 
formed  at  the  upper  part  of  the  abdominal 
cavity ;  the  intestine,  which  is  already  some- 
what convoluted,  and  occupies  its  central 
portion  ;  and  the  Wolffian  bodies,  which  pro- 
ject on  each  side  the  spinal  column. 

The   Wolffian   bodies,  in   their  intimate 
structure,  closely  resemble  the  adult  kidney.      They  consist  of 
secreting  tubules,  lined  with  epithelium,  which  run  from  the  outer 
toward  the  inner  edge  of  the  organ,  terminating  at  their  free  ex- 


F(ETAL  Pig,  %  of  an  inch 
lonif ;  from  a  «pecimen  in  the 
author's  possession.  1.  Heart. 
2.  Anterior  extremity.  3.  Pos- 
terior extremity.  4.  Wolffiaa 
body.  The  abdominal  Tvalls 
have  been  cut  away,  in  order 
to  show  the  position  of  the 
Wolffian  bodies. 


656  DEVELOPMENT    OF    THE    KIDNEYS. 

tremities  in  small  rounded  dilatations.  Into  eacli  of  these  dilated 
extremities  is  received  a  globular  coil  of  capillary  bloodvessels,  or 
glomerulus,  similar  to  that  of  the  adult  kidney.  The  tubules  of  the 
Wolffian  body  all  empty  into  a  common  excretory  duct,  which  leaves 
the  organ  at  its  lower  extremity,  and  communicates  afterward  with 
the  lower  part  of  the  intestinal  canal,  just  at  the  point  where  the 
diverticulum  of  the  allantois  is  given  off,  and  where  the  urinary 
bladder  is  afterward  to  be  situated.  The  principal,  if  not  the 
only  distinction,  between  the  minute  structure  of  the  Wolffian 
bodies  and  that  of  the  true  kidneys,  consists  in  the  size  of  the 
tubules  and  of  their  glomeruli,  these  elements  being  considerably 
larger  in  the  Wolffian  body  than  in  the  kidney.  In  the  foetal 
pig,  for  example,  when  about  an  inch  and  a  half  in  length,  the 
diameter  of  the  tubules  of  the  Wolffian  body  is  ^J^  of  an  inch, 
while  in  the  kidney  of  the  same  foetus,  the  diameter  of  the  tubules 
is  only  725  of  an  inch.  The  glomeruli  in  the  Wolffian  bodies 
measure  -^^  of  an  inch  in  diameter,  while  those  of  the  kidney  mea- 
sure only  Y^^  of  an  inch.  The  Wolffian  bodies  are  therefore  urinary 
oro^ans,  so  far  as  regards  their  anatomical  structure,  and  are  some- 
times known,  accordingly,  by  the  name  of  the  "false  kidneys." 
There  is  little  doubt  that  they  perform,  at  this  early  period,  a  func- 
tion analogous  to  that  of  the  kidneys,  and  separate  from  the  blood 
of  the  embryo  an  excrementitious  fluid  which  is  discharged  by  the 
ducts  of  the  organ  into  the  cavity  of  the  allantois. 

Subsequently,  the  Wolffian  bodies  increase  for  a  time  in  size, 
though  not  so  rapidly  as  the  rest  of  the  body ;  and  consequently 
their  relative  magnitude  diminishes.  Still  later,  they  begin  to 
suffer  an  absolute  diminution  or  atrophy,  and  become  gradually 
less  and  less  perceptible.  In  the  human  subject,  they  are  hardly 
to  be  detected  after  the  end  of  the  second  month  (Longet),  and  in 
the  quadrupeds  also  they  completely  disappear  long  before  birth. 
They  are  consequently  foetal  organs,  destined  to  play  an  important 
part  during  a  certain  stage  of  development,  but  to  become  after- 
ward atrophied  and  absorbed,  as  the  physiological  condition  of  the 
foetus  alters.  During  the  period,  however,  of  their  retrogression 
and  atrophy,  other  organs  appear  in  their  neighborhood,  which 
become  afterward  permanently  developed.  These  are,  first,  the 
kidneys,  and  secondly,  the  internal  organs  of  generation. 

The  kidneys  are  formed  just  behind  the  Wolffian  bodies,  and  are 
at  first  entirely  concealed  by  them  in  a  front  view,  the  kidneys 
being  at  this  time  not  more  than  a  fourth  or  a  fifth  part  the  size  of 


VrOLFFIAN    BODIES. 


657 


Fig.  2.7. 


FffiTAL  Pig,  one  and  a  half 
inches  long.  From  a  specimen  in 
the  author's  possession. — 1.  Wolffiia 
hody,     2.  Kidney. 


the  Wolffian  bodies.  (Fig.  247.)  As  the  kidneys,  however,  subse- 
quently enlarge,  while  the  Wolffian  bodies  diminish,  the  propor- 
tions existing  between  the  two  organs  are 
reversed ;  and  the  Wolffian  bodies  at  last 
come  to  be  mere  small  rounded  or  ovoid 
masses,  situated  on  the  anterior  surface 
of  the  kidneys.  (Figs.  248  and  249.)  The 
kidneys,  during  this  period,  grow  more 
rapidly  in  an  upward  than  in  a  downward 
direction,  so  that  the  Wolffian  bodies 
come  to  be  situated  near  their  inferior 
extremity,  and  seem  to  have  performed 
a  sliding  movement  from  above  down- 
ward, over  their  anterior  surface.  This 
apparent  sliding  movement,  or  descent 
of  the  Wolffian  bodies,  is  owing  entirely 
to  the  rapid  growth  of  the  kidneys  in  an 
upward  direction,  as  we  have  already  explained. 

The  kidneys,  during  the  succeeding  periods  of  fcetal  life,  become 
in  their  turn  very  largely  developed  in  proportion  to  the  rest  of  the 
organs;  attaining  a  size,  in  the  foetal  pig,  equal  to  ^^  (in  weight) 
of  the  entire  body.  This  proportion,  however,  diminishes  again 
very  considerably  before  birth,  owing 
to  the  increased  development  of  other 
parts.  In  the  human  foetus  at  birth, 
the  weight  of  the  two  kidneys  taken 
together  is  y^g  that  of  the  entire 
body. 

Internal  Organs  of  Generation.  — 
About  the  same  time  that  the  kidneys 
are  formed  behind  the  Wolffian  bodies, 
two  oval-shaped  organs  make  their 
appearance  in  front,  on  the  inner  side  of 
the  Wolffian  bodies  and  between  them 
and  the  spinal  column.  These  bodies  are 
the  internal  organs  of  generation ;  viz., 
the  testicles  in  the  male,  and  the  ovaries 
in   the   female.     At  first  they  occupy 

precisely  the  same  situation  and  present  precisely  the  same  appear 
ance,  whether  the  foetus  is  afterward  to  belong  to  the  male  or  the 
female  sex.  (Fig.  248.) 
42 


Internal  Organs  op  Gene- 
ration, &c.  ;  in  a  fcetal  pig  three 
inches  long.  From  a  specimen  in  the 
author's  possession. — 1,  1.  Kidneys. 
2,2.  Wolffian  bodies.  3,3.  Internal 
organs  of  generation  ;  testicbs  or 
ovaries.  4.  Urinary  bladder  tamed 
over  in  front.     5.  Intestine. 


658  DEVELOPMENT    OF    THE    KIDNEYS. 

A  short  distance  above  the  internal  organs  of  generation  there 
commences,  on  each  side,  a  narrow  tube  or  duct,  which  runs  from 
above  downward  along  the  anterior  border  of  the  "Wolffian  body, 
immediately  in  front  of  and  parallel  with  the  excretory  duct  of  this 
organ.  The  two  tubes,  right  and  left,  then  approach  each  other 
below ;  and,  joining  upon  the  median  line,  empty,  together  with 
the  ducts  of  the  Wolffian  bodies,  into  the  base  of  the  allantois,  or 
what  will  afterward  be  the  base  of  the  urinary  bladder.  These  tubes 
serve  as  the  excretory  ducts  of  the  internal  organs  of  generation ; 
and  will  afterward  become  the  vasa  deferentia  in  the  male,  and  the 
Fallopian  tubes  in  the  female.  According  to  Coste,  the  vasa  defe- 
rentia at  an  early  period  are  disconnected  with  the  testicles ;  and 
originate,  like  the  Fallopian  tubes,  by  free  extremities,  presenting 
each  an  open  orifice.  It  is  only  afterward,  according  to  the  same 
author,  that  the  vasa  deferentia  become  adherent  to  the  testicles,  and 
a  communication  is  established  between  them  and  the  tubuli  semi- 
niferi.  In  the  female,  the  Fallopian  tubes  remain  permanently 
disconnected  with  the  ovaries,  except  by  the  edge  of  the  fimbriated 
extremity ;  which  in  many  of  the  lower  animals  becomes  closely 
adherent  to  the  ovary,  and  envelopes  it  more  or  less  completely. 

Male  Organs  of  Generation;  Descent  of  the  Testicles. — In  the  male 
foetus  there  now  commences  a  movement  of  translation,  or  change 
of  place,  in  the  internal  organs  of  generation,  which  is  known  as 
the  "  descent  of  the  testicles."  In  consequence  of  this  movement, 
the  above  organs,  which  are  at  first  placed  near  the  middle  of  the 
abdomen,  and  directly  in  front  of  the  kidneys,  come  at  last  to  be 
situated  in  the  scrotum,  altogether  outside  and  below  the  abdominal 
cavity.  They  also  become  inclosed  in  a  distinct  serous  sac  of  their 
own,  the  tunica  vaginalis  testis.  This  apparent  movement  of  the 
testicles  is  accomplished  in  the  same  manner  as  that  of  the  Wolf- 
fian bodies,  above  mentioned,  viz.,  by  a  disproportionate  growth  of 
the  middle  and  upper  portions  of  the  abdomen  and  of  the  organs 
situated  above  the  testicles,  so  that  the  relative  position  of  these 
organs  becomes  altered.  The  descent  of  the  testicles  is  accompanied 
by  certain  other  alterations  in  the  organs  themselves  and  their 
appendages,  which  take  place  in  the  following  manner. 

By  the  upward  enlargement  of  the  kidneys,  both  the  Wolffian 
bodies  and  the  testicles  are  soon  found  to  be  situated  near  the 
lower  extremity  of  these  organs.  (Fig.  249.)  At  the  same  time,  a 
slender  rounded  cord  (not  represented  in  the  figure)  passes  from 
the  lower  extremity  of  each  testicle  in  an  outward  and  downward 


MALE  ORGANS  OF  GENERATION. 


659 


Fig.  249. 


Inter XAL  Orgaks  of  Generatiok, 
&c.,  in  a  foetal  pig  nearly  four  inches  long. 
From  a  specimen  in  the  author's  possession. — 
1,  1.  Kidneys.  2,  2.  Wolffian  bodies.  3,  3. 
Testicles.     4.  Urinary  bladder.     5.  Intestine. 


direction,  crossing  the  corresponding  vas  deferens  a  short  distance 
above  its  union  with  its  fellow  of  the  opposite  side.  Below  this 
point,  the  cord  spoken  of  continues  to  run  obliquely  outward  and 
downward;  and,  passing  through 
the  abdominal  walls  at  the  situa- 
tion of  the  inguinal  canal,  is  in- 
serted into  the  subcutaneous  tis- 
sues near  the  symphysis  '  pubis. 
The  lower  part  of  this  cord  be- 
comes the  guhernaculum  testis  ;  and 
muscular  fibres  are  soon  developed 
in  its  substance  which  may  be 
easily  detected,  even  in  the  human 
foetus,  during  the  latter  half  of 
gestation.  At  the  period  of  birth, 
however,  or  soon  afterward,  these 
muscular  fibres  disappear  and  can 
no  longer  be  recognized. 

All  that  portion  of  the  excre- 
tory tube  of  the  testicle  which  is  situated  outside  the  crossing  of  the 
gubernaculum,  is  destined  to  become  afterward  convoluted,  and 
converted  into  the  epididymis.  That  portion  which  is  situated  in- 
side the  same  point  remains  comparatively  straight,  but  becomes 
considerably  elongated,  and  is  finally  known  as  the  vas  deferens. 

As  the  testicles  descend  still  farther  in  the  abdomen,  they  con- 
tinue to  grow,  while  the  Wolffian  bodies,  on  the  contrary,  diminish 
rapidly  in  size,  until  the  latter  become  much  smaller  than  the  tes- 
ticles ;  and  at  last,  when  the  testicles  have  arrived  at  the  internal 
inguinal  ring,  the  Wolffian  bodies  have  altogether  disappeared,  or 
at  least  have  become  so  much  altered  that  their  characters  are  no 
longer  recognizable.  In  the  human  foetus,  the  testicles  arrive  at 
the  internal  inguinal  ring,  about  the  termination  of  the  sixth  month 
(Wilson). 

During  the  succeeding  month,  a  protrusion  of  the  peritoneum 
takes  place  through  the  inguinal  canal,  in  advance  of  the  testicle ; 
while  the  last  named  organ  still  continues  its  descent.  As  it  then 
passes  downward  into  the  scrotum,  certain  muscular  fibres  are  given 
off  from  the  lower  border  of  the  internal  oblique  muscle  of  the 
abdomen,  growing  downward  with  the  testicle,  in  such  a  manner  as 
to  form  a  series  of  loops  upon  it,  and  upon  the  elongating  spermatic 
cord.     These  loops  constitute  afterward  the  cremaster  muscle. 


660  r-EVELOPMENT    OF    THE    KIDNEYS. 

At  last,  the  testicles  descend  fairly  to  the  bottom  of  the  scrotum, 
the  gubernaculum  constantly  shortening,  and  the  vas  deferens 
elongating  as  it  proceeds.  The  convoluted  portion  of  the  efferent 
duct,  viz.,  the  epididymis,  then  remains  closely  attached  to  the  body 
of  the  testicle;  while  the  vas  deferens  passes  upward,  in  a  reverse 
direction,  enters  the  abdomen  through  the  inguinal  canal,  again 
bends  downward,  and  joins  its  fellow  of  the  opposite  side ;  after 
which  they  both  open  into  the  prostatic  portion  of  the  urethra  by 
distinct  orifices,  situated  on  each  side  the  median  line.  At  the 
same  time,  two  diverticula  arise  from  the  median  portion  of  the 
vasa  deferentia,  and,  elongating  in  a  backward  direction,  underneath 
the  base  of  the  bladder,  become  developed  into  two  compound 
sacculated  reservoirs — the  vesiculse  seminales. 

The  left  testicle  is  a  little  later  in  its  descent  than  the  right,  but 
it  afterward  passes  farther  into  the  scrotum,  and,  in  the  adult  condi- 
tion, usually  hangs  a  little  lower  than  its  fellow  of  the  opposite  side. 
After  the  testicle  has  fairly  passed  into  the  scrotum,  the  serous 
pouch,  which  preceded  its  descent,  remains  for  a  time  in  communi- 
cation with  the  peritoneal  cavity.     In  many  of  the  lower  animals, 
as,  for  example,  the  rabbit,  this  condition  is  permanent ;  and  the 
testicle,  even  in  the  adult  animal,  may  be  alternately  drawn  down- 
ward into  the  scrotum,  or  retracted  into 
Fig.  250.  the  abdomen,  by  the  action  of  the  guber- 

naculum and  the  cremaster  muscle.  But 
in  the  human  foetus,  the  two  opposite 
surfaces  of  the  peritoneal  pouch,  covering 
the  testicle,  approach  each  other  at  the 
inguinal  canal,  forming  at  that  point  a 
constriction  or  neck,  which  partly  shuts 
off  the  testicle  from  the  cavity  of  the 
abdomen.  By  a  continuation  of  this  pro- 
cess, the  serous  surfaces  come  actually 
Formation  of   Tunica    va-    in  coutact  with  cach  othcp,  and,  adhering 

oiNAi.is    Testis.— 1.   Testicle        ,  ,  ,     ,i  •  •,        ,•  /-n-         c^m       \ 

neavly  at  the  bottom  of  the  scro-      tOgCthcr     at    thlS     SltUatlOU    (Big.    250,    4), 

turn.  2  Cavity  of  tauica  va-inHiis.     ^Q^m  E  kind  of  cicatrlx.  Or  umbiHcus,  by 

3.  Cavity  of  peritoneum.  4.  Ohliter-         ,  ^  ^  ^    ^ 

ated  neck  of  peritoneal  sac.  the  complctc  closupe  and  consolidation  of 

which  the  cavity  of  the  tunica  vaginalis 
(2)  is  finally  shut  off  altogether  from  the  general  cavity  of  the 
peritoneum  (3).  The  tunica  vaginalis  testis  is,  therefore,  originally 
a  part  of  the  peritoneum,  from  which  it  is  subsequently  separated 
by  the  process  just  described. 


FEMALE  ORGANS  OF  GENERATION".         661 

The  separation  of  the  tunica  vaginalis  from  the  peritoneum  is 
usually  completed  in  the  human  subject  before  birth.  But  some- 
times it  fails  to  take  place  at  the  proper  time,  and  the  intestine  is 
then  apt  to  protrude  into  the  scrotum,  in  front  of  the  spermatic 
cord,  giving  rise,  in  this  way,  to  a  congenital  inguinal  hernia.  (Fig. 
251.)  The  parts  implicated,  however,  in  this  malformation,  have 
still,  as  in  the  case  of  congenital  umbili- 
cal hernia,  a  tendency  to  unite  with  each  Fig.  251. 
other  and  obliterate  the  unnatural  open- 
ing ;  and  if  the  intestine  be  retained  by 
pressure  in  the  cavity  of  the  abdomen, 
cicatrization  usually  takes  place  at  the 
inguinal  canal,  and  a  cure  is  effected. 

The  descent  of  the  testicle,  above  de- 
scribed, is  not  accomplished  by  the  forci- 
ble traction  of  the  muscular  fibres  of  the 
gubernaculum,  as  has  been  described  by 
certain  writers,  but  bv  a  simple  process       congenital  inguinal  heh- 

„  ,         ,   .  .       "^  .       ,.-i  ^  NiA.— 1.     Testicle.     2,2,2.    lute*- 

01  growth  takmg  place  m  diiierent  parts,     tine, 
in    different    directions,    at     successive 

periods  of  foetal  life.  The  gubernaculum,  accordingly,  has  no 
proper  function  as  a  muscular  organ,  in  the  human  subject,  but  is 
merely  the  anatomical  vestige,  or  analogue,  of  a  corresponding 
muscle  in  certain  of  the  lower  animals,  where  it  has  really  an 
important  function  to  perform.  For  in  them,  as  we  have  already 
mentioned,  both  the  gubernaculum  and  the  cremaster  remain  fully 
developed  in  the  adult  condition,  and  are  then  employed  to  elevate 
and  depress  the  testicle,  by  the  alternate  contraction  of  their  mus- 
cular fibres. 

Female  Organs  of  Generation. — At  an  early  period,  as  we  have 
mentioned  above,  the  ovaries  have  the  same  external  appearance, 
and  occupy  the  same  position  in  the  abdomen,  as  the  testicles  in  the 
opposite  sex.  The  descent  of  the  ovaries  also  takes  place,  to  a  great 
extent,  in  the  same  manner  with  the  descent  of  the  testicles.  When, 
in  the  early  part  of  this  descent,  they  have  reached  the  level  of  the 
lower  edge  of  the  kidneys,  a  cord,  analogous  to  the  gubernaculum, 
may  be  seen  proceeding  from  their  lower  extremity,  crossing  the 
efferent  duct  on  each"  side,  and  passing  downward,  to  be  attached 
to  the  subcutaneous  tissues  at  the  situation  of  the  inguinal  ring. 
That  part  of  the  duct  situated  outside  the  crossing  of  this  cord, 
becomes  afterward  convoluted,  and  is  converted  into  the  FaHojAan 


662  DEVELOPMENT    OF    THE    KIDNEYS,    ETC. 

tube ;  while  that  point  which  is  inside  the  same  point,  becomes  con- 
verted into  the  uterus.  The  upper  portion  of  the  cord  itself  becomes 
the  ligament  of  the  ovary  ;  its  lower  portion,  the  round  ligament  of 
the  uterus. 

As  the  ovaries  continue  their  descent,  they  pass  below  and  be- 
hind the  Fallopian  tubes,  which  necessarily  perform  at  the  same 
time  a  movement  of  rotation,  from  before  backward  and  from 
above  downward ;  the  whole,  together  with  the  ligaments  of  the 
ovaries  and  the  round  ligaments,  being  enveloped  in  double  folds 
of  peritoneum,  which  enlarge  with  the  growth  of  the  parts  them- 
selves, and  constitute  finally  the  broad  ligaments  of  the  uterus. 

It  will  be  seen  from  what  has  been  said  above,  that  the  situation 
occupied  by  the  "Wolffian  bodies  in  the  female  is  always  the  space 
between  the  ovaries  and  the  Fallopian  tubes;  for  the  "Wolffian 
bodies  accompany  the  ovaries  in  their  descent,  just  as,  in  the  male, 
they  accompany  the  testicles.  As  these  bodies  now  become  grad- 
ually atrophied,  their  glandular  structure  disappears  altogether ; 
but  their  bloodvessels,  in  many  instances,  remain  as  a  convoluted 
vascular  plexus,  occupying  the  situation  above  mentioned.  The 
"Wolffian  bodies  may  therefore  be  said,  in  these  instances,  to  un- 
dergo a  kind  of  vascular  degeneration.  This  peculiar  degeneration 
is  quite  evident  in  the  "Wolffian  bodies  of  the  foetal  pig,  some  time 
before  the  organs  have  entirely  lost  their  original  form.  In  the 
cow,  a  collection  of  convoluted  bloodvessels  may  be  seen,  even  in 
the  adult  condition,  near  the  edge  of  the  ovary,  and  between  the 
two  folds  of  peritoneum  forming  the  broad  ligament.  These  are 
undoubtedly  vestiges  of  the  Wolffian  bodies,  which  have  undergone 
the  vascular  degeneration  above  described. 

"While  the  above  changes  are  taking  place  in  the  adjacent  organs, 
the  two  lateral  halves  of  the  uterus  fuse  with  each  other  more  and 
more  upon  the  median  line,  and  become  covered  with  an  exces- 
sively developed  layer  of  muscular  fibres.  In  the  lower  animals, 
the  uterus  remains  divided  at  its  upper  portion,  running  out  into 
two  long  conical  tubes  or  cornua  (Fig.  182),  presenting  the  form 
known  as  the  uterus  bicornis.  In  the  human  subject,  however,  the 
fusion  of  the  two  lateral  halves  of  the  organ  is  nearly  complete ; 
so  that  the  uterus  presents  externally  a  rounded,  but  somewhat 
flattened  and  triangular  figure  (Fig,  183),  with  the  ligaments  of  the 
ovary  and  the  round  ligaments  passing  off  from  its  superior  angles. 
But,  internally,  the  cavity  of  the  organ  still  presents  a  strongly 
marked  triangular  form,  the  vestige  of  its  original  division. 


FEMALE  ORGANS  OF  GENERATION".         663 

Occasionally  the  human  uterus,  even  in  the  adult  condition,  re- 
mains divided  into  two  lateral  portions  by  a  vertical  septum,  which 
runs  from  the  middle  of  its  fundus  downward  toward  the  os  in- 
ternum. This  septum  may  even  be  accompanied  by  a  partial 
external  division  of  the  organ,  corresponding  with  it  in  direction 
and  producing  the  malformation  known  as  "uterus  bicornis."  or 
"  double  uterus." 

The  OS  internum  and  os  externum  are  produced  by  partial  con- 
strictions of  the  original  generative  passage ;  and  the  anatomical 
distinctions  between  the  body  of  the  uterus,  the  cervix  and  the 
vagina,  are  produced  by  the  different  development  of  the  mucous 
membrane  and  muscular  tunic  in  its  corresponding  portions. 
During  foetal  life,  however,  the  neck  of  the  uterus  grows  mucb 
faster  than  its  body;  so  that,  at  the  period  of  birth,  the  entire 
organ  is  very  far  from  presenting  the  form  which  it  exhibits  in  the 
adult  condition.  In  the  human  foetus  at  term,  the  cervix  uteri 
constitutes  nearly  two-thirds  of  the  entire  length  of  the  organ; 
while  the  body  forms  but  little  over  one-third.  The  cervix,  at 
this  time,  is  also  much  larger  in  diameter  than  the  body ;  so  that 
the  whole  organ  presents  a  tapering  form  from  below  upward. 
The  arbor  vitae  uterina  of  the  cervix  is  at  birth  very  fully  de- 
veloped, and  the  mucous  membrane  of  the  body  is  also  thrown 
into  three  or  four  folds  which  radiate  upward  from  the  os  internum. 
The  cavity  of  the  cervix  is  filled  with  a  transparent  semi-solid 
mucus. 

The  position  of  the  uterus  at  birth  is  also  different  from  that 
which  it  assumes  in  adult  life ;  nearly  the  entire  length  of  the  organ 
being  above  the  level  of  the  symphysis  pubis,  and  its  inferior 
extremity  passing  below  that  point  only  by  about  a  quarter  of  an 
inch.  It  is  also  slightly  anteflexed  at  the  junction  of  the  body  and 
cervix.  After  birth,  the  uterus,  together  with  its  appendages,  con- 
tinues to  descend ;  until,  at  the  period  of  puberty,  its  fundus  is 
situated  just  below  the  level  of  the  symphysis  pubis. 

The  ovaries  at  birth  are  narrow  and  elongated  in  form.  They 
contain  at  this  time  an  abundance  of  eggs;  each  inclosed  in  a 
Graafian  follicle,  and  averaging  g^y  of  an  inch  in  diameter.  The 
vitellus,  however,  is  imperfectly  formed  in  most  of  them,  and  in 
some  is  hardly  to  be  distinguished.  The  Graafian  follicle  at  this 
period  envelopes  each  egg  closely,  there  being  nothing  between  its 
internal  surface  and  the  exterior  of  the  Qgg,  excepting  the  thin 
layer  of  cells  forming  the  "membrana  granulosa."     Inside  this 


GQ'i  DEVELOPMENT  OF  THE  KIDNEYS,  ETC. 

layer  is  to  be  seen  the  germinative  vesicle,  with,  the  germinative 
spot,  surrounded  bj  a  faintly  granular  vitellus,  more  or  less 
abundant  in  different  parts.  Some  of  the  Graafian  follicles  con- 
taining eggs  are  as  large  as  4^(5-  of  an  inch;  others  as  small  as  ttj^s^- 
In  the  very  smallest,  the  cells  of  the  membrana  granulosa  appear 
to  fill  entirely  the  cavity  of  the  follicle,  and  no  vitellus  or  germina- 
tive vesicle  is  to  be  seen. 


DEVELOPMENT   OF    THE    CIRCULATORY   APPARATUS.      665 


\  CHAPTER   XVII. 

DEVELOPMENT    OF    THE    CIRCULATORY 
APPARATUS. 

Theri  are  three  distinct  forms  or  phases  of  development  assumed 
by  the  ciiculatory  system  during  different  periods  of  life.  These 
different  fcrms  of  the  circulation  are  intimately  connected  with  the 
manner  in  vhich  nutrition  and  respiration,  or  the  renovation  of  the 
blood,  are  accomplished  at  different  epochs ;  and  they  follow  each 
other  in  the  progress  of  development,  as  different  organs  are  em- 
ployed in  tun  to  accomplish  the  above  functions.  The  first  form 
is  that  of  the  vitelline  circulation,  which  exists  at  a  period  when  the 
vitellus,  or  the  umbilical  vesicle,  is  the  sole  source  of  nutrition  for 
the  foetus.  The  second  is  the  placental  circulation,  which  lasts 
through  the  greater  part  of  foetal  life,  and  is  characterized  by  the 
existence  of  the  placenta ;  and  the  third  is  the  complete  or  adult 
circulation,  in  whicl  the  renovation  and  nutrition  of  the  blood  are 
provided  for  by  the  lungs  and  the  intestinal  canal. 

First,  or  Vitelline  Circulation. — It  has  already  been  shown,  in  a 
previous  chapter,  that  when  the  body  of  the  embryo  has  begun  to 
be  formed  in  the  centie  of  the  blastodermic  membrane,  a  number 
of  bloodvessels  shoot  out  from  its  sides,  and  ramify  over  the 
remainder  of  the  vitelline  sac,  forming,  by  their  inosculation,  an 
abundant  vascular  plexus  The  area  occupied  by  this  plexus  in  the 
blastodermic  membrane  around  the  foetus  is,  as  we  have  seen,  the 
"  area  vasculosa."  In  the  ■^.gg  of  the  fowl  (Fig.  252),  the  plexus  is 
limited,  on  its  external  border,  by  a  terminal  vein  or  sinus — the 
"  sinus  terminalis ;"  and  the  blood  of  the  embryo,  after  circulating 
through  the  capillaries  of  tht  plexus,  returns  by  several  venous 
branches,  the  two  largest  of  wtich  enter  the  body  near  its  anterior 
and  posterior  extremities.  Th«  area  vasculosa  is,  accordingly,  a 
vascular  appendage  to  the  circdatory  apparatus  of  the  embryo, 
spread  out  over  the  surface  of  the  vitellus  for  the  purpose  of  absorb- 
ing from  it  the  nutritious  material  requisite  for  the  growth  of  the 


666      DEVELOPMENT    OF    THE    CIRCULATORY    APPARATUS. 

newlj-formed  tissues.  In  the  egg  of  the  fish  (Fig,  253),  the  princi- 
pal vein  is  seen  passing  up  in  front  underneath  the  head ;  while  the 
arteries  emerge  all  along  the  lateral  edges  of  the  body.     The  ensire 

Fig.  252. 


Eao  OP  Fowl  in  process  of  development,  showing  area  vascalosa,  with  vitelline  circulation, 
teiminal  sinus,  &c. 


Fis.  253. 


\ritellus,  in  this  way,  becomes  covered  with  an  al)undant  vascular 
network,  connected  with  the  internal  circulation  of  the  foetus  by 
arteries  and  veins. 

Very  soon,  as  the  embryo  and  the  entire  egg  increase  in  size, 
there  are  two  arteries  and  two  veins  which  become 
larger  than  the  others,  and  which  subsequently 
do  the  whole  work  of  conveying  the  blood  of 
the  foetus  to  and  from  the  area  vasculosa.  These 
two  arteries  emerge  from  the  lateral  edges  of 
the  foetus,  on  the  right  and  left  sides ;  while  the 
two  veins  re-enter  at  aiout  the  same  point,  and 
nearly  parallel  with  them.  These  four  vessels  are 
then  termed  the  omjhalo-mesenteric  arteries  and 
veins. 

The  arrangement  of  the  circulatory  apparatus 
in  the  interior  of  the  body  of  the  foetus,  at  this  time,  is  as  follows  : 
The  heart  is  situated  at  the  median  iine,  just  beneath  the  head  and 
in  front  of  the  oesophagus.  It  receives  at  its  lower  extremity  the 
trunks  of  the  two  omphalo-mesenteric  veins,  and  at  its  upper 
extremity  divides  into  two  vessels,  which,  arching  over  backward, 
attain  the  anterior  surface  of  the  vertebral  column,  and  then  run 
from  above  downward   along  ihe   spine,  quite   to   the   posterior 


Ego  of  Fish  (Jar- 
rabacca),  showing  vitel- 
line  circulation. 


PLACENTAL    CIRCULATION. 


667 


extremity  of  the  foetus.  These  arteries  are  called  the  vertebral 
arteries,  on  account  of  their  course  and  situation,  running  parallel 
with  the  vertebral  column.  They  give  oft)  throughout  their  course, 
many  small  lateral  branches,,  which  supply  the  body  of  the  foetus, 
and  also  two  larger  branches — the  omphalo-mesenteric  arteries — 
which  pass  out,  as  above  described,  into  the  area  vasculosa.  The 
two  vertebral  arteries  remain  separate  in  the  upper  part  of  the  bod  v, 
but  soon  fuse  with  each  other  a  little  below  the  level  of  the  heart ; 
so  that,  below  this  point,  there  remains  afterward  but  one  large 
artery,  the  abdominal  aorta,  running  from  above  downward  along 
the  median  line,  giving  off  the  omphalo-mesenteric  arteries  to  the 
area  vasculosa,  and  supplying  smaller  branches  to  the  body,  the 
walls  of  the  intestine,  and  the  other  organs  of  the  foetus. 

The  above  description  shows  the  origin  and  formation  of  the  first 
or  vitelline  circulation.  A  change,  however,  now  begins  to  take 
place,  by  which  the  vitellus  is  superseded,  as  an  organ  of  nutrition, 
by  the  placenta,  which  takes  its  place ;  and  the  second  or  placental 
circulation  becomes  established  in  the  following  manner : — 

Second  Circulation. — After  the  umbilical  vesicle  has  been  formed 
by  the  process  already  described,  a  part  of  the  vitellus  remains  in- 
cluded in  it,  while  the  rest  is  retained  in  the  abdomen  and  inclosed 
in  the  intestinal  canal.  As  these 
two  organs  (umbilical  vesicle  and 
intestine)  are  originally  parts  of 
the  same  vitelline  sac,  they  remain 
supplied  by  the  same  vascular 
system,  viz :  the  omphalo-mesen- 
teric vessels.  Those  which  remain 
within  the  abdomen  of  the  foetus 
supply  the  mesentery  and  intes- 
tine ;  but  the  larger  trunks  pass 
outward,  and  ramify  upon  the 
walls  of  the  umbilical  vesicle. 
(Fig.  254.)  At  first,  there  are, 
as  we  have  mentioned  abov^, 
two  omphalo-mesenteric  arteries 
emerging  from  the  body,  and  two 
omphalo-mesenteric  veins  return- 
ing to  it ;  but  soon  afterward,  the  two  arteries  are  replaced  by  a 
common  trunk,  while  a  similar  change  takes  place  in  the  two  veins. 
Subsequently,  therefore,  there  remains  but  a  single  artery  and  a 


Diagram  of  Young  Embryo  and  ire 
Vhssels,  showing  circulation  of  unibiliru! 
vesicle,  and  also  that  of  allantois,  beginning  to 
be  formed. 


668      DEVELOPMENT    OF    THE    CIRCULATOEY    APPARATUS. 

single  vein,  connecting  the  internal  and  external  portions  of  the 
vitelline  circulation. 

The  vessels  belonging  to  this  system  are  therefore  called  the 
omphalo-mesenteric  vessels,  because  a  part  of  them  (omphalic  ves- 
sels) pass  outward,  by  the  umbilicus,  or  "  omphalos,"  to  the  umbili- 
cal vesicle,  while  the  remainder  (mesenteric  vessels)  ramify  upon 
the  mesentery  and  the  intestine. 

At  first,  the  circulation  of  the  umbilical  vesicle  is  more  import- 
ant than  that  of  the  intestine ;  and  the  omphalic  artery  and  vein 
appear  accordingly  as  large  trunks,  of  which  the  mesenteric  ves- 
sels are  simply  small  branches.  (Fig.  25-i.)  Afterward,  however, 
the  intestine  rapidly  enlarges,  while  the  nmbilical  vesicle  dimi- 
nishes, and  the  proportions  existing  between  the  two  sets  of  vessels 
are  therefore  reversed.   (Fig.  255.)     The  mesenteric  vessels  then 

Fig.  255. 


Diagram  of  Embkto  and  its  Vrssrls:  showing  the  second  circniation.  The  pharynx, 
oesophagas,  and  intestinal  canal,  have  hecome  further  developed,  and  the  mesenteric  arteries  have 
eularged,  while  the  nrahilical  vesicle  and  its  vascular  branches  are  very  much  reduced  in  size.  The 
large  umbilical  arteries  are  seen  passing  out  to  the  placenta. 

come  to  be  the  principal  trunks,  while  the  omphalic  vessels  are 
simply  minute  branches,  running  out  along  the  slender  cord  of  the 
umbilical  vesicle,  and  ramifying  in  a  few  scanty  twigs  upon  its 
surface. 


DEVELOPMENT    OF    THE    ARTERIAL    SYSTEM.  669 

In  the  mean  time,  the  allantois  is  formed  by  a  protrusion  from 
the  lower  extremity  of  the  intestine,  which,  carrying  with  it  two 
arteries  and  two  veins,  passes  out  by  the  anterior  opening  of  the 
body,  and  comes  in  contact  with  the  external  membrane  of  the 
egg.  The  arteries  of  the  allantois,  which  are  termed  the  umhiliral 
arteries,  are  supplied  by  branches  of  the  abdominal  aorta ;  the  um- 
bilical veins,  on  the  other  hand,  join  the  mesenteric  veins,  and 
empty  with  them  into  the  venous  extremity  of  the  heart.  As  the 
umbilical  vesicle  diminishes,  the  allantois  enlarges ;  and  the  latter 
soon  becomes  converted,  in  the  human  subject,  into  a  vascular 
chorion,  a  part  of  which  is  devoted  to  the  formation  of  the  placenta. 
(Fig.  255.)  As  the  placenta  soon  becomes  the  only  source  of  nutri- 
tion for  the  foetus,  its  vessels  are  at  the  same  time  very  much 
increased  in  size,  and  preponderate  over  all  the  other  parts  of  the 
circulatory  system.  During  the  early  periods  of  the  formation  of 
the  placenta,  there  are,  as  we  have  stated  above,  two  umbilical 
arteries  and  two  umbilical  veins.  But  subsequently  one  of  the 
veins  disappears,  and  the  whole  of  the  blood  is  returned  to  the  body 
of  the  foetus  by  the  other,  which  becomes  enlarged  in  proportion. 
For  a  long  time  previous  to  birth,  therefore,  there  are  in  the  umbili- 
cal cord  two  umbilical  arteries,  and  but  a  single  umbilical  vein. 

Such  is  the  second,  or  placental  circulation.  It  is  exchanged,  at 
the  period  of  birth,  for  the  third  or  aduU  circulation,  in  which  the 
blood  which  had  previously  circulated  through  the  placenta,  is 
diverted  to  the  lungs  and  the  intestine.  These  are  the  oigans 
upon  which  the  whole  system  afterward  depends  for  the  nourish- 
ment and  renovation  of  the  blood. 

During  the  occurrence  of  the  above  changes,  certain  other  altera- 
tions take  place  in  the  arterial  and  venous  systems,  which  will  now 
require  to  be  described  by  themselves. 

Development  of  the  Arterial  System. — At  an  early  period  of  deve- 
lopment, as  we  have  shown  above,  the  principal  arteries  pass  off 
from  the  anterior  extremity  of  the  heart  in  two  arches,  which  curve 
backward  on  each  side,  from  the  front  of  the  body  toward  the 
vertebral  column,  after  which  they  again  become  longitudinal  in 
direction,  and  receive  the  name  of  "vertebral  arteries."  Very  soon 
these  arches  divide  successively  into  two,  three,  four,  and  five 
secondary  arches,  placed  one  above  the  other,  along  the  sides  of 
the  neck,  (Fig.  256.)  These  are  termed  the  cervical  arches.  In  the 
fish,  these  cervical  arches  remain  permanent,  and  give  off  from  their 
convex  borders  the  branchial  arteries,  in  the  form  of  vascular  tufts, 


670      DEVELOPMENT    OF    THE    CIRO-ULATORY   APPARATUS. 

to  the  gills  on  each  side  of  the  neck ;  but  in  the  human  subject  and 
the  quadrupeds,  the  branchial  tufts  are  never  developed,  and  the 
cervical  arches,  as  well  as  the  trunks  with  which  they  are  con- 
nected, become  modified  by  the  progress  of  development  in  the 
followinDT  manner: — 


Fitr.  256. 


Fig.  257. 


Early  coDdition  of  Arterial  System: 
Bhowiug  the  heart  (1),  with  Its  two  ascend- 
ing arterial  trunks,  giving  off  on  each  side 
live  cervical  arches,  which  terminate  in  the 
vertebral  arteries  (2,  2).  The  vertebral  arte- 
ries unite  below  the  heart  to  form  the 
aorta  (3). 


Adult  condition  of  Akt  kk  i  a  l  Sts 
T  E  M  .—1,  1.  Carotids.  2,  2.  Vertebrals 
3,  3.  Right  and  left  subclavian^.  4,  4 
Eight  and  left  superior  inrercostals.  5, 
Left  aortic  arch,  which  remains  perma- 
nent. 6.  Bight  aortic  arch,  which  dis 
appears. 


The  two  ascending  arterial  trunks  on  the  anterior  part  of  the 
neck,  from  which  the  cervical  arches  are  given  off)  become  con- 
verted into  the  carotids.  (Fig.  257,  1,1.)  The  fifth,  or  uppermost 
cervical  arch,  remains  at  the  base  of  the  brain  as  the  inosculation, 
through  the  circle  of  Willis,  between  the  internal  carotids  and  the 
basilar  artery,  which  is  produced  by  the  union  of  the  two  verte- 
brals. The  next,  or  fourth  cervical  arch,  may  be  recognized  in  an 
inosculation  which  is  said  to  be  very  constant  between  the  superior 
thyroid  arteries,  branches  of  the  carotids,  and  the  inferior  thyroids, 
which  come  from  the  subclavians  at  nearly  the  same  point  from 
which  the  vertebrals  are  given  off.  The  next,  or  third  cervical  arch, 
remains  on  each  side,  as  the  subclavian  artery  (3,  3).     This  vessel, 


DEVELOPMENT   OF    THE    ARTERIAL    SYSTEM.  671 

though  at  first  a  mere  branch  of  commuaication  between  the  caro- 
tid and  the  vertebral,  has  now  increased  in  size  to  such  an  extent 
that  it  has  become  the  principal  trunk,  from  which  the  vertebral 
itself  is  given  off  as  a  small  branch.  Immediately  below  this  point 
of  intersection,  also,  the  vertebral  artery  diminishes  very  much  in 
relative  size,  loses  its  connection  with  the  abdominal  aorta,  and 
supplies  only  the  first  two  intercostal  spaces,  under  the  name  of  the 
superior  intercostal  artery  (4,  4).  The  second  cervical  arch  becomes 
altered  in  a  very  different  manner  on  the  two  opposite  sides.  On 
the  left  side,  it  becomes  enormously  enlarged,  so  as  to  give  off,  as 
secondary  branches,  all  the  other  arterial  trunks  which  have  been 
described,  and  is  converted  in  this  manner  into  the  arch  of  the 
aorta  (5).  On  the  right  side,  however,  the  corresponding  arch  (e) 
becomes  smaller  and  smaller,  and  at  last  altogether  disappears ;  so 
that,  finally,  we  have  only  a  single  aortic  arch,  projecting  to  the 
left  of  the  median  line,  and  continuous  with  the  thoracic  and  abdo- 
minal aorta. 

The  first  cervical  arch  remains  during  foetal  life  upon  the  left 
side,  as  the  ''  ductus  arteriosus,"  presently  to  be  described.  In  the 
adult  condition,  however,  it  has  disappeared  equally  upon  the  right 
and  left  sides.  In  this  way  the  permanent  condition  of  the  arterial 
circulation  is  gradually  established  in  the  upper  part  of  the  body. 

Corresponding  changes  take  place,  however,  during  the  same 
time,  in  the  lower  part  of  the  body.  Here  the  abdominal  aorta 
runs  undivided,  upon  the  median  line,  quite  to  the  end  of  the 
spinal  column ;  giving  off'  on  each  side  snaccessive  lateral  branches, 
which  supply  the  intestine  and  the  parietes  of  the  body.  When 
the  allantois  begins  to  be  developed,  two  of  these  lateral  branches 
accompany  it,  and  become,  consequently,  the  umbilical  arteries. 
These  two  vessels  increase  so  rapidly  in  size,  that  they  soon  appear 
as  divisions  of  the  aortic  trunk ;  while  the  original  continuation  of 
this  trunk,  running  to  the  end  of  the  spinal  column,  appears  only 
as  a  small  branch  given  off  at  the  point  of  bifurcation.  When  the 
lower  limbs  begin  to  be  developed,  they  are  supplied  by  two  small 
branches,  given  off'  from  the  umbilical  arteries  near  their  origin. 

Up  to  this  time  the  pelvis  and  posterior  extremities  are  but 
slightly  developed.  Subsequently,  however,  they  grow  more 
rapidly,  in  proportion  to  the  rest  of  the  body,  and  the  arteries 
which  supply  them  increase  in  a  corresponding  manner.  That 
portion  of  the  umbilical  arteries,  lying  between  the  bifurcation  of 
the  aorta  and  the  origin  of  the  branches  going  to  the  lower  ex- 


672      DEVELOPMENT    OF    THE    CIRCULATORY    APPARATUS. 


tremities,  becomes  the  common  iliacs,  "wMcli  in  their  turn  afterward 
divide  into  the  umbilical  arteries  proper,  and  the  femorals.  Sub- 
sequently, by  the  continued  growth  of  the  pelvis  and  lower 
extremities,  the  relative  size  of  their  vessels  is  still  further  in- 
creased ;  and  at  last  the  arterial  system  in  this  part  of  the  body 
assumes  the  arrangement  which  belongs  to  the  latter  periods  of 
gestation.  The  aorta  divides,  as  before,  into  the  two  common  iliacs. 
These  also  divide  into  the  external  iliacs,  supplying  the  lower  ex- 
tremities, and  the  internal  iliacs,  supplying  the  pelvis ;  and  this 
division  is  so  placed  that  the  umbilical  or  hypogastric  arteries  arise 
from  the  internal  iliacs,  of  which  they  now  appear  to  be  secondary 
branches. 

After  the  birth  of  the  foetus,  and  the  separation  of  the  placenta, 
the  hypogastric  arteries  become  partially  atrophied,  and  are  con- 
verted, in  the  adult  condition,  into  solid,  rounded  cords,  running 
upward  toward  the  umbilicus.  Their  lower  portion,  however, 
remains  pervious,  and  gives  off  arteries  supplying  the  urinary 
bladder.  The  obliterated  hypogastric  arteries,  therefore,  the  rem- 
nants of  the  original  umbilical  or  allantoic  arteries,  run  upward 
from  the  internal  iliacs  along  the  sides  of  the 
Fig.  258.  urinary  bladder,  which  is  the  remnant  of  the  ori- 

ginal allantois  itself.  The  terminal  continuation 
of  the  original  abdominal  aorta,  is  the  arteria 
sacra  media,  which,  in  the  adult,  runs  downward 
on  the  anterior  surface  of  the  sacrum,  supplying 
branches  to  the  rectum  and  the  anterior  sacral 
nerves. 

Development  of  the  Venous  System. — According 
to  the  observations  of  M.  Coste,  the  venous  system 
at  first  presents  the  same  simplicity  and  symmetry 
with  the  arterial.  The  principal  veins  of  the 
body  consist  of  two  long  venous  trunks,  the  ver- 
tehral  veins  (Fig.  258),  which  run  along  the  sides 
of  the  spinal  column,  parallel  with  the  vertebral 
arteries.  They  receive  in  succession  all  the  inter- 
costal veins,  and  empty  into  the  heart  by  two 
lateral  trunks  of  equal  size,  the  canals  of  Cuvier. 
When  the  inferior  extremities  become  developed, 
their  two  veins,  returning  from  below,  join  the 
vertebral  veins  near  the  posterior  portion  of  the 
body ;    and,  crossing  them,  afterward  unite  with  each  other,  thus 


Early  conditioQ  of  Ve- 
nous System;  show- 
ing the  vertebral  veins 
emptying  into  the  heart 
by  two  lateral  trunks, 
the  "canals  of  Cuvier." 


DEVELOPMENT    OF    THE    VENOUS    SYSTEM. 


673 


constituting  another  vein  of  new  formation 
(Fig.  259,  a),  which  runs  upward  a  little  to  the 
right  of  the  median  line,  and  empties  by  itself 
into  the  lower  extremity  of  the  heart.  The 
two  branches,  by  means  of  which  the  veins  of 
the  lower  extremities  thus  unite,  become  after- 
ward, by  enlargement,  the  common  iliac  veins ; 
while  the  single  trunk  (a)  resulting  from  their 
union  becomes  the  ve7ia  cava  inferior.  Subse- 
quently, the  vena  cava  inferior  becomes  very 
much  larger  than  the  vertebral  veins ;  and  its 
two  branches  of  bifurcation  are  afterward  re- 
presented by  the  two  iliacs. 

Above  the  level  of  the  heart,  the  vertebral 
and  intercostal  veins  retain  their  relative  size 
until  the  development  of  the  superior  extremi- 
ties has  commenced.  Then  two  of  the  inter- 
costal veins  increase  in  diameter  (Fig.  259),  and 
become  converted  into  the  right  and  left  sub- 
clavians ;  while  those  portions  of  the  vertebral 
veins  situated  above  the  subclavians  become  the 
right  and  left  jugulars.  Just  below  the  junction 
of  the  jugulars  with  the  subclavians,  a  small 
branch  of  communication  now  appears  between 
the  two  vertebrals(Fig.  259,  h),  passing  over  from 
left  to  right,  and  emptying  into  the  right  verte- 
bral vein  a  little  above  the  level  of  the  heart ;  so 
that  a  part  of  the  blood  coming  from  the  left  side 
of  the  head,  and  the  left  upper  extremity,  still 
passes  down  the  left  vertebral  vein  to  the  heart 
upon  its  own  side,  while  a  part  crosses  over  by 
the  communicating  branch  (6),  and  is  finally 
conveyed  to  the  heart  by  the  right  descending 
vertebral.  Soon  afterward,  this  branch  of  com- 
munication enlarges  so  rapidly  that  it  prepon- 
derates altogether  over  the  left  superior  verte- 
bral vein,  from  which  it  originated  (Fig.  260), 
and,  serving  then  to  convey  all  the  blood  coming 
from  the  left  side  of  the  head  and  left  upper 
extremity  over  to  the  right  side  above  the  heart, 
it  becomes  the  left  vena  innominaia. 
43 


Fig.  259. 


Venous  System  far- 
ther advanced,  showing 
formation  of  iliac  and  sub- 
clavian veins. — a.  Vein  of 
new  formation,  which  be- 
comes the  inferior  vena 
cava.  h.  Transverse  branch 
of  new  formation,  which 
afterward  becomes  the  left 
vena  innominata. 

Fig.  260, 


Further  development  of 
the  Venous  System. — 
The  vertebral  veins  are 
much  diminished  in  size, 
and  the  canal  of  Cuvier,  on 
the  left  side,  is  gradually 
disappearing.  C.  Trans- 
Verne  branch  of  new  forma- 
tion, which  is  to  becoma 
the  vena  azygos  minor. 


674      DEVELOPMENT    OF    THE    CIRCULATORY   APPARATUS. 


Fig.  261. 


On  the  left  side,  that  portion  of  the  superior  vertebral  vein,  which 
is  below  the  subclavian,  remains  as  a  small  branch  of  the  vena  in- 
nominata,  receiving  the  six.  or  seven  upper  intercostal  veins ;  while 
on  the  right  side  it  becomes  excessively  enlarged,  receiving  the 
blood  of  both  jugulars  and  both  subclavians,  and  is  converted  into 
the  vena  cava  superior. 

The  left  canal  of  Cuvier,  by  which  the  left  vertebral  vein  at  first 
communicates  with  the  heart,  subsequently  becomes  atrophied  and 
disappears;  while  on  the  right  side  it  becomes  excessively  enlarged, 
and  forms  the  lower  extremity  of  the  vena  cava  superior. 

The  superior  and  inferior  venas  cav^,  accordingly,  do  not  cor- 
respond with  each  other  so  far  as  regards  their 
mode  of  origin,  and  are  not  to  be  regarded  as 
analogous  veins.  For  the  superior  vena  cava 
is  one  of  the  original  vertebral  veins;  while 
the  inferior  vena  cava  is  a  totally  distinct  vein, 
of  new  formation,  resulting  from  the  union  of 
the  two  lateral  trunks  coming  from  the  infe- 
rior extremities. 

The  remainder  of  the  vertebral  veins  finally 
assume  the  condition  shown  in  Fig.  261,  which 
is  the  complete  or  adult  form  of  the  venous 
circulation.  At  the  lower  part  of  the  abdomen, 
the  vertebral  veins  send  inward  small  trans- 
verse branches,  which  communicate  with  the 
vena  cava  inferior,  between  the  points  at  which 
they  receive  the  intercostal  veins.  These 
branches  of  communication,  by  increasing  in 
size,  become  the  lumbar  veins  (7),  which,  in  the 
adult  condition,  communicate  with  each  other 
by  arched  branches,  a  short  distance  to  the  side- 
of  'the  vena  cava.  Above  the  level  of  the 
lumbar  arches,  the  vertebral  veins  retain  their 
original  direction.  That  upon  the  right  side 
still  receives  all  the  right  intercostal  veins,  and 
becomes  the  vena  azygos  major  (s).  It  also 
receives  a  small  branch  of  communication  from 
its  fellow  of  the  left  side  (Fig.  260,  c),  and  this  branch  soon  enlarges 
to  such  an  extent  as  to  bring  over  to  the  vena  azygos  major  all  the 
blood  of  the  five  or  six  lower  intercostal  veins  of  the  left  side, 
becoming,  in  this  way,  the  vena  azygos  minor  (9).     The  six  or  seven 


Adult  condition  of  Ve- 
nous System. — 1.  Rig  lit 
auricle  of  heart.  2.  Vena 
cava  superior.  3,  3.  Jugular 
veins.  4,4.  Subclavian  vein.s. 
5.  Vena  cava  inferior.  6,  6. 
Iliac  veins.  7.  Lumbar  veins. 
8.  Vena  azygos  major.  9. 
Vena  azygos  minor.  10.  Su- 
perior intercostal  vein. 


DEVELOPMENT    OF    THE    HEPATIC    CIRCULATION.        675 

upper  intercostal  veins  on  tlie  left  side  still  empty,  as  before,  into 
their  own  vertebral  vein  (lo),  wliicli,  joining  the  left  vena  innomi- 
nata  above,  is  known  as  the  superior  intercostal  vein.  The  left  canal 
of  Cuvier  has  by  this  tinae  entirely  disappeared ;  so  that  all  the 
venous  blood  now  enters  the  heart  by  the  superior  or  the  inferior 
vena  cava.  But  the  original  vertebral  veins  are  still  continuous 
throughout,  though  very  much  diminished  in  size  at  certain  points ; 
since  both  the  greater  and  lesser  azygous  veins  inosculate  below 
with  the  superior  lumbar  veins,  and  the  superior  intercostal  vein 
also  inosculates  below  with  the  lesser  azygous,  just  before  it  passes 
over  to  the  right  side. 

There  are  still  two  parts  of  the  circulatory  apparatus,  the  deve- 
lopment of  which  presents  peculiarities  sufficiently  important  to 
be  described  separately.  These  are,  first,  the  liver  and  the  ductus 
venosus,  and  secondly,  the  heart,  with  the  ductus  arteriosus. 

Development  of  the  Hepatic  Circulation  and  the  Ductus  Venosus. — 
The  liver  appears  at  a  very  early  period  in  the  upper  part  of  the 
abdomen,  as  a  mass  of  glandular  and  vascular  tissue,  which  is  deve- 
loped around  the  upper  portion  of  the 
omphalo-mesenteric  vein,  just  below  its  ^^S-  ^62. 

termination  in  the  heart.  (Fig.  262.)     As  f  / 

soon  as  the  organ  has  attained  a  con-         S^V-n  I 

siderable   size,   the    omphalo-mesenteric         BteaO  J 

vein  (i)  breaks  up  in  its  interior  into  a         ^^^jjj^g^  ^ 
capillary  plexus,  the  vessels   of  which  f^^^^j^^ 

unite  again  into  venous  trunks,  and  so  ^^^^ 

convey  the  blood  finally  to  the  heart.  ■---i-r- 

The  omphalo-mesenteric  vein  below  the      Eariy  form  of  hepatic  cie- 

T  ,1  1  ,^  ,7        .  T  •!        CCLATION.       1.     Omphalo-mesen- 

liverthenbecomes  the  portoZmn;  while  teric  veiu.  2.  Hepatic  vein.  3. 
above  the  liver,  and  between  that  organ    Heart.    The  dotted  line  shows  the 

-       ,  ,  .  .  ,  „     eituatioa  of    the   future    umbilical 

and  the   heart,  it  receives  the  name  oi    vein. 
the  hepatic  vein  (2).     The  liver,  accord- 
ingly, is  at  this  time  supplied  with  blood  entirely  by  the  portal  vein, 
coming  from  the  umbilical  vesicle  and  the  intestine ;  and  all  the 
blood  derived  from  this  source  must  pass  through  the  hepatic  cir- 
culation before  reaching  the  venous  extremity  of  the  heart. 

But  soon  afterward  the  allantois  makes  its  appearance,  and  be- 
comes rapidly  developed  into  the  placenta ;  and  the  umbilical  vein 
coming  from  it  joins  the  omphalo-mesenteric  vein  in  the  substance 
of  the  liver,  and  takes  part  in  the  formation  of  the  hepatic  capillary 
plexus.    As  the  umbilical  vesicle,  however,  becomes  atrophied,  and 


676      DEVELOPMENT    OF    THE    CIRCULATORY    APPARATUS. 


Fig.  263. 


Hepatic  CiRCtTLATiON 
farther  advanced. — 1.  Portal  vein. 
2  Umbilical  vein.  .3.  Hepatic 
vein. 


the  intestine  also  remains  inactive,  while  the  placenta  increases  in 
size  and  in  functional  importance,  a  time  soon  arrives  when  the 

liver  receives  more  blood  bj  the  umbilical 
vein  than  by  the  portal  vein.  (Fig.  263.) 
The  umbilical  vein  then  passes  into  the 
liver  at  the  longitudinal  fissure,  and  sup- 
plies the  left  lobe  entirely  with  its  own 
branches.  To  the  right  it  sends  off  a  large 
branch  of  communication,  which  opens  in- 
to the  portal  vein,  and  partially  supplies 
the  right  lobe  with  umbilical  blood.  The 
liver  is  thus  supplied  with  blood  from  two 
different  sources,  the  most  abundant  of 
which  is  the  umbilical  vein ;  and  all  the 
blood  entering  the  liver  circulates,  as  be- 
fore, through  its  capillary  vessels. 

But  we  have  already  seen  that  the  liver  is  much  larger,  in  pro- 
portion to  the  entire  body,  at  an  early  period  of  foetal  life  than  in 
the  later  months.     In  the  foetal  pig,  when  very  young,  it  amounts 

to  nearly  twelve  per  cent,  of  the 
weight  of  the  whole  body ;  but  be- 
fore birth  it  diminishes  to  seven,  six, 
and  even  three  or  four  per  cent.  For 
some  time,  therefore,  previous  to 
birth,  there  is  much  more  blood  re- 
turned from  the  placenta  than  is  re- 
quired for  the  capillary  circulation 
of  the  liver.  Accordingly,  a  vascular 
duct  or  canal  is  formed  in  its  interior, 
by  which  a  portion  of  the  placental 
blood  is  carried  directly  through  the 
organ,  and  conveyed  to  the  heart 
without  having  passed  through  the 
hepatic  capillaries.  This  duct  is 
called  the  Ductus  venosus. 

The  ductus  venosus  is  formed  by  a 
gradual  dilatation  of  one  of  the  he- 
patic capillaries  at  (5)  (Fig.  264),  which,  enlarging  excessively,  be- 
comes at  last  converted  into  a  wide  canal,  or  branch  of  communi- 
cation, passing  directly  from  the  umbilical  vein  below  to  the  hepatic 
vein  above.     The  circulation  through  the  liver,  thus  established,  is 


Fi?.  264. 


Hepatic  Ctkcci. ation-  daring  lat- 
ter part  of  foetal  life. — 1.  Portal  vein.  2. 
Umbilical  vein.  3.  Left  branch  of  umbili- 
cal vein.  4.  Right  branch  of  umbilical 
vein.  5.  Ductus  venosus.  6.  Hepatic 
vein. 


DEVELOPMENT    OF    THE    HEPATIC    CIRCULATION.       677 


Fig.  265. 


as  follows :  A  certain  quantity  of  venous  blood  still  enters  through 
the  portal  vein  (i),  and  circulates  in  a  part  of  the  capillary  system 
of  the  right  lobe.  The  umbilical  vein  (2),  bringing  a  much  larger 
quantity  of  blood,  enters  the  liver  also,  a  little  to  the  left,  and  the 
blood  which  it  contains  divides  into  three  principal  streams.  One 
of  them  passes  through  the  left  branch  (3)  into  the  capillaries  of  the 
left  lobe ;  another  turns  off'  through  the  right  branch  (4),  and,  join- 
ing the  blood  of  the  portal  vein,  circulates  through  the  capillaries 
of  the  right  lobe ;  while  the  third  passes  directly  onward  through 
the  venous  duct  (5),  and  reaches  the  hepatic  vein  without  having 
passed  through  any  part  of  the  capillary  plexus. 

This  condition  of  the  hepatic  circulation  continues  until  birth. 
At  that  time,  two  important  changes  take  place.  First,  the  pla- 
cental circulation  is  altogether  cut  oft';  and  secondly,  a  much  larger 
quantity  of  blood  than  before  begins 
to  circulate  through  the  lungs  and 
the  intestine.  The  superabundance 
of  blood,  previously  coming  from  the 
placenta,  is  now  diverted  into  the 
lungs ;  while  the  intestinal  canal,  en- 
tering upon  the  active  performance  of 
its  functions,  becomes  the  sole  source 
of  supply  for  the  hepatic  venous 
blood.  The  following  changes,  there- 
fore, take  place  at  birth  in  the  ves- 
sels of  the  liver.  (Fig.  265.)  First, 
the  umbilical  vein  shrivels  and  be- 
comes converted  into  a  solid  rounded 
cord  (a).  This  cord  may  be  seen,  in 
the  adult  condition,  running  from  the 
internal  surface  of  the  abdominal 
walls,  at  the  umbilicus,  to  the  longi- 
tudinal fissure  of  the  liver.  It  is  then 
known  under  the  name  of  the  round 

ligament.  Secondly,  the  ductus  venosus  also  becomes  obliterated, 
and  converted  into  a  fibrous  cord.  Thirdly,  the  blood  entering  the 
liver  by  the  portal  vein  (1),  passes  off  by  its  right  branch,  as  before, 
to  the  right  lobe.  But  in  the  branch  (4),  the  course  of  the  blood  is 
reversed.  This  was  formerly  the  right  branch  of  the  umbilical 
vein,  its  blood  passing  in  a  direction  from  left  to  right.  It  now 
becomes  the  left  branch  of  the  portal  vein ;  and  its  blood  passes 


Adult  form  of  Hepatic  Circtla- 
TioN.  —  1.  Portal  vein.  2.  Obliterated 
umbilical  vein,  forming  the  round  liga- 
ment; the  continuation  of  the  dotted 
lines  through  the  liver  shows  the  situa- 
tion of  the  obliterated  ductus  venosus. 
3.  Hepatic  vein.  4.  Left  branch  of  portal 
vein. 


678      DEVELOPiMENT    OF    THE    CIRCULATORY    APPARATLIS. 

from  right  to  left,  to  be  distributed  to  the  capillaries  of  the  left 
lobe. 

According  to  Dr.  Guy,  the  umbilical  vein  is  completely  closed  at 
the  end  of  the  fifth  day  after  birth. 

Development  of  the  Heart,  and  the  Ductus  Arteriosus. — When  the 
embryonic  circulation  is  first  established,  the  heart  is  a  simple  tubu- 
lar sac  (Fig.  266),  receiving  the  veins  at  its  lower  extremity,  and 
giving  off  the  arterial  trunks  at  its  upper  extremity.  By  the  pro- 
gress of  its  growth,  it  soon  becomes  twisted  upon  itself;  so  that  the 
entrance  of  the  veins,  and  the  exit  of  the  arteries,  come  to  be  placed 
more  nearly  upon  the  same  horizontal  level  (Fig.  267);  but  the 
entrance  of  the  veins  (i)  is  behind  and  a  little  below,  while  the  exit 
of  the  arteries  (2)  is  in  front  and  a  little  above.  The  heart  is,  at 
this  time,  a  simple  twisted  tube ;  and  the  blood  passes  through  it 
in  a  single  continuous  stream,  turning  upon  itself  at  the  point  of 
curvature,  and  passing  directly  out  by  the  arterial  orifice. 

Fig.  266.  Fig.  267. 

2 


i 

rcETAL  Heakt,  divided 

Earliest  form  of  FcET  A  L  Fcetal    Hkart,    twisted  into  riglit  and  left  cavities. — 

Heart.  —  1.  Venous  ex-        upon    itself. — 1.    Venous   ex-  1.      Venous    extremity.      2. 

tremity.     2.   Arterial  ex-        tremity.      2.    Arterial   extre-  Arterial      extremity.      3,   3. 

tremity.  mity.  Pulmonary  branches. 

Soon  afterward,  this  single  cardiac  tube  is  divided  into  two  paral- 
lel tubes,  right  and  left,  by  a  longitudinal  partition,  which  grows 
from  the  inner  surface  of  its  walls  and  follows  the  twisted  course 
of  the  organ  itself.  (Fig.  268.)  This  partition,  which  is  indicated 
in  the  figure  by  a  dotted  line,  extends  a  short  distance  into  the 
commencement  of  the  primitive  arterial  trunk,  dividing  it  into  two 
lateral  halves,  one  of  which  is  in  communication  with  the  right  side 
pf  the  heart,  the  other  with  the  left. 

About  the  same  time,  the  pulmonary  branches  (3,  3)  are  given 
off  from  each  side  of  the  arterial  trunk  near  its  origin;  and  the 
longitudinal  partition,  above  spoken  of,  is  so  placed  that  both  these 
branches  fall  upon  one  side  of  it,  and  are  both,  consequently,  given 
off  from  that  division  of  the  artery  which  is  connected  with  the  right 
side  of  the  heart. 


DEVELOTMENT    OF    THE    HEART. 


679 


FcetalHeakt  still  farther 
developed. — 1  Aorta.  2.  Piw- 
monary  artery.  3,  3.  Pui- 
Konary  branches  4.  Ductus 
arteriosus. 


Yerj  soon  a  superficial  line  of  demarcation,  or  furrow,  shows 
itself  upon  the  external  surface  of  the  heart,  corresponding  in  situa- 
tion  with  the  internal  septum;  while  at  the  root  of  the  arterial 
trunk  this  furrow  becomes  much  deeper,  and  finally  the  two  lateral 
portions  of  the  vessel  are  separated  from  each  other  altogether,  in 
the  immediate  neighborhood  of  the  heart, 
joining  again,  however,  a  short  distance  be- 
yond the  origin  of  the  pulmonary  branches. 
(Fig.  269.)  It  then  becomes  evident  that 
the  left  lateral  division  of  the  arterial  trunk 
is  the  commencement  of  the  aorta  (i);  while 
its  right  lateral  division  is  the  trunk  of  the 
pulmonary  artery  {2),  giving  off'  the  right 
and  left  pulmonary  branches  (3,3),  at  a  short 
distance  from  its  origin.  That  portion  of 
the  pulmonary  trunk  (4)  which  is  beyond 
the  origin  of  the  pulmonary  branches,  and 
which  communicates  freely  Avith  the  aorta,  is  the  Ductus  arteriosus. 

The  ductus  arteriosus  is  at  first  as  large  as  the  pulmonary  trunk 
itself;  and  nearly  the  whole  of  the  blood,  coming  from  the  right 
ventricle,  passes  directly  onward  through  the  arterial  duct,  and 
enters  the  aorta  without  going  to  the  lungs.  But  as  the  lungs 
gradually  become  developed,  they  require  a  larger  quantity  of 
blood  for  their  nutrition,  and  the  pulmonary  branches  increase  in 
proportion  to  the  pulmonary  trunk  and  the  ductus  arteriosus.  At 
the  termination  of  foetal  life,  in  the 
human  subject,  the  ductus  arteriosus 
is  about  as  large  as  either  one  of  the 
pulmonary  branches ;  and  a  yqtj  con- 
siderable portion  of  the  blood,  there- 
fore, coming  from  the  right  ventricle 
still  passes  onward  to  the  aorta  with- 
out being  distributed  to  the  lungs. 

But  at  the  period  of  birth,  the  lungs 
enter  upon  the  active  performance  of 
the  function  of  respiration,  and  imme- 
diately require  a  much  larger  supply 
of  blood.  The  right  and  left  pul- 
monary branches  then  enlarge,  so  as 
to  become  the  two  principal  divisions 
of  the  pulmonary  trunk,  (Fig.  270.) 


Fisr.  270. 


Heart  of  Infant,  shoTvin>,'  dis- 
appearance of  arterial  duct  after  hirtb 
—1  Aorta.  2.  Pulmonary  artery.  3, 
3.  Pulmonary  branches  4.  Ductus 
arteriosus  becoming  obliterated. 

The  ductus  arteriosus  at  the 


680      DEVELOPMENT    OF    THE    CIRCULATORY    APPARATUS. 

same  time  becomes  contracted  and  shrivelled  to  such  an  extent 
that  its  cavity  is  obliterated ;  and  it  is  finally  converted  into  an  im- 
pervious, rounded  cord,  which  remains  until  adult  life,  running 
from  the  point  of  bifurcation  of  the  pulmonary  artery  to  the  under 
side  of  the  arch  of  the  aorta.  The  obliteration  of  the  arterial  duct 
is  complete,  at  latest,  by  the  tenth  week  after  birth.  (Gruy.) 

The  two  auricles  are  separated  from  the  two  ventricles  by  hori- 
zontal septa  which  grow  from  the  internal  surface  of  the  cardiac 
walls ;  but  these  septa  remaining  incomplete,  the  auriculo- ventricu- 
lar orifices  continue  pervious,  and  allow  the  free  passage  of  the 
blood  from  the  auricles  to  the  ventricles. 

The  interventricular  septum,  or  that  which  separates  the  two 
ventricles  from  each  other,  is  completed  at  a  very  early  date ;  but 
the  interauricular  septum,  or  that  which  is  situated  between  the 
two  auricles,  remains  incomplete  for  a  long  time,  being  perforated 
by  an  oval-shaped  opening,  the  foramen  ovale,  allowing,  at  this 
situation,  a  free  passage  from  the  right  to  the  left  side  of  the  heart. 
The  existence  of  the  foramen  ovale  and  of  the  ductus  arteriosus 
gives  rise  to  a  peculiar  crossing  of  the  streams  of  blood  in  passing 
through  the  heart,  which  is  characteristic  of  foetal  life,  and  which 
may  be  described  as  follows : — 

It  will  be  found  upon  examination  that  the  two  venae  cavae, 
superior  and  inferior,  do  not  open  into  the  auricular  sac  on  the 
same  plane  or  in  the  same  direction ;  for  while  the  superior  vena 
cava  is  situated  anteriorly,  and  is  directed  downward  and  forward, 
the  inferior  is  situated  quite  posteriorly,  and  passes  into  the  auricle 
in  a  direction  from  right  to  left,  and  transversely  to  the  axis  of 
the  heart.  A  nearly  vertical  curtain  or  valve  at  the  same  time 
hangs  downward  behind  the  orifice  of  the  superior  vena  cava  and 
in  front  of  the  orifice  of  the  inferior.  This  curtain  is  formed  by 
the  lower  edge  of  the  septum  of  the  auricles,  which,  as  we  have 
before  stated,  is  incomplete  at  this  age,  and  which  terminates 
inferiorly  and  toward  the  right  in  a  crescentic  border,  leaving  at 
that  part  an  oval  opening,  the  foramen  ovale.  The  stream  of  blood, 
coming  from  the  superior  vena  cava,  falls  accordingly  in  front  of 
this  curtain,  and  passes  directly  downward,  through  the  auriculo- 
ventricular  orifice,  into  the  right  ventricle.  But  the  inferior  vena 
cava,  being  situated  farther  back  and  directed  transversely,  opens, 
properly  speaking,  not  into  the  right  auricle,  but  into  the  left ;  for 
its  stream  of  blood,  falling  behind  the  curtain  above  mentioned, 
passes  across,  through  the  foramen  ovale,  directly  into  the  cavity  of 


DEVELOPMENT    OF    THE    HEART. 


681 


the  left  auricle.  This  direction  of  the  carrent  of  blood,  cominor 
from  the  inferior  vena  cava,  is  further  secured  by  a  peculiar  mem- 
branous valve,  which  exists  at  this  period,  termed  the  Eustachian 
valve.  This  valve,  which  is  very  thin  and  transparent  (Fig.  271,/), 
is  attached  to  the  anterior  border  of  the  orifice  of  the  inferior  vena 
cava,  and  terminates  by  a  cresceutic  edge,  directed  toward  the  left ; 
the  valve,  in  this  way,  standing 

as  an  incomplete  membranous  Fig.  271. 

partition  between  the  cavity  of 
the  inferior  vena  cava  and  that 
of  the  right  auricle.  A  bougie, 
accordingly,  placed  in  the  in- 
ferior vena  cava,  as  shown  in 
Fig.  271,  lies  naturally  quite 
behind  the  Eustachian  valve, 
and  passes  directly  through 
the  foramen  ovale,  into  the  left 
auricle. 

The  two  streams  of  blood, 
therefore,  coming  from  the  su- 
perior and  inferior  ven^  cavae, 
cross  each  other  upon  entering 
the  heart.  This  crossing  of  the 
streams  does  not  take  place, 
however,  as  it  is  sometimes 
described,  in  the  cavity  of  the 
right  auricle ;  but,  owing  to  the 
peculiar  position  and  direction 
of  the  two  veins  at  this  period, 
with  regard  to  the  septum  of 

the  auricles,  the  stream  coming  from  the  superior  vena  cava  enters 
the  right  auricle  exclusivel}^,  while  that  from  the  inferior  passes 
almost  directly  into  the  left  auricle. 

It  will  also  be  seen,  by  examining  the  positions  of  the  aorta,  pul 
monary  artery,  and  ductus  arteriosus,  at  this  time,  that  the  arteria 
innominata,  together  with  the  left  carotid  and  left  subclavian,  are 
given  off  from  the  arch  of  the  aorta,  before  its  junction  with  the 
ductus  arteriosus,  and  this  arrangement  causes  the  blood  of  the  two 
venae  cavse,  not  only  to  enter  the  heart  in  different  directions,  but 
also  to  be  distributed,  after  leaving  the  ventricles,  to  different  parts 
of  the  body.  (Fig.  272.)     For  the  blood  of  the  superior  vena  cava 


Heart  OF  Human  F(e tub,  at  the  end  of  the 
sixth  month  ;  from  a  specimen  in  tlieanthor'spos- 
sessiou. — a.  Inferior  vena  cava.  h.  Superior  vena 
cava.  c.  Cavity  of  right  auricle,  laid  open  from 
the  front,  d.  Appendix  auricularis.  e.  Carit"  ol 
right  ventricle,  also  laid  open.  /.  Eustachian  valve. 
The  bougie,  which  is  placed  in  the  inferior  vena 
cava,  can  be  seen  passing  behind  the  Eustachian 
valve,  just  below  the  point  indicated  by  /,  then 
crossing  behind  the  cavity  of  the  right  auiicle,  and 
passing  through  the  foramen  ovale,  to  the  left  side 
of  the  heart. 


682      DEVELOPMENT    OF    THE    CIKCULATORY    APPARATUS. 


Fig   272. 


passes  througli  the  right  auricle  downward  into  the  right  ventricle, 
thence  through  the  pulmonary  artery  and  ductus  arteriosus,  into 
the  thoracic  aorta,  while  the  blood  of  the  inferior  vena  cava,  enter- 
ing the  left  auricle,  passes  into  the  left  ventricle,  thence  into  the  arch 
of  the  aorta,  and  is  distributed  to  the  head  and  upper  extremities, 
before  reaching  the  situation  of  the  arterial  duct.  The  two  streams, 
therefore,  in  passing  through  the  heart,  cross  each  other  both  behind 
and  in  front.     The  venous  blood,  returning  from  the  head  and 

upper  extremities  by  the  superior 
vena  cava,  passes  through  the  abdo- 
minal aorta  and  the  umbilical  arte- 
ries, to  the  lower  part  of  the  body, 
and  to  the  placenta ;  while  that  re- 
turning from  the  placenta,  by  the 
inferior  vena  cava,  is  distributed  to 
the  head  and  upper  extremities, 
through  the  vessels  given  off  from 
the  arch  of  the  aorta. 

This  division  of  the  streams  of 
blood,  during  a  certain  period  of 
foetal  life,  is  so  complete  that  Dr. 
John  Eeid,'  on  injecting  the  infe- 
rior vena  cava  with  red,  and  the 
superior  with  yellow,  in  a  seven 
months'  human  foetus,  found  that 
the  red  had  passed  through  the  foramen  ovale  into  the  left  auricle 
and  ventricle  and  arch  of  the  aorta,  and  had  filled  the  vessels  of 
the  head  and  upper  extremities ;  while  the  yellow  had  passed  into 
the  right  ventricle,  pulmonary  artery,  ductus  arteriosus,  and  tho- 
racic aorta,  with  only  a  slight  admixture  of  red  at  the  posterior 
part  of  the  right  auricle.  All  the  branches  of  the  thoracic  and 
abdominal  aorta  were  filled  with  yellow,  while  the  whole  of  the  red 
had  passed  to  the  upper  part  of  the  body. 

"We  have  repeated  the  above  experiment  several  times  on  the 
foetal  pig,  when  about  one-half  and  three-quarters  grown,  first  taking 
the  precaution  to  wash  out  the  heart  and  large  vessels  with  a  wa- 
tery injection,  immediately  after  the  removal  of  the  foetus  from  the 
body  of  the  parent,  and  before  the  blood  had  been  allowed  to  coagu- 
late.    The  injections  used  were  blue  for  the  superior  vena  cava, 


Diagram  of  Circulatiom  TnRonoH 
THE  FcETAL  Hbart. — «.  Superior  vena 
cava.  6.  Inferior  vena  cava.  c,c,c,c.  Avch 
of  aorta  and  its  branches,  d.  Pulmonary 
artery. 


'  Edinburgh  Medical  and  Surgical  Journal,  vol.  xliii.  1835. 


DEVELOPMENT    OF    THE    HEART.  683 

and  yellow  for  the  inferior.  The  two  syringes  were  managed,  at 
the  same  time,  by  the  right  and  left  hands ;  their  nozzles  beino- 
firmly  held  in  place  by  the  fingers  of  an  assistant.  When  the 
points  of  the  syringes  were  introduced  into  the  veins,  at  equal  dis- 
tances from  the  heart,  and  the  two  injections  made  with  equal  force 
and  rapidity,  it  was  found  that  the  admixture  of  the  colors  which 
took  place  was  so  slight,  that  at  least  nineteen-twentieths  of  the 
yellow  injection  had  passed  into  the  left  auricle,  and  nineteen-twen- 
tieths of  the  blue  into  the  right.  The  pulmonary  artery  and  ductus 
arteriosus  contained  a  similar  proportion  of  blue,  and  the  arch  of 
the  aorta  of  yellow.  In  the  thoracic  and  abdominal  aorta,  however, 
contrary  to  what  was  found  by  Dr.  Eeid,  there  was  always  an  ad- 
mixture of  the  two  colors,  generally  in  about  equal  proportions. 
This  discrepancy  may  be  owing  to  the  smaller  size  of  the  head  and 
upper  extremities,  in  the  pig,  as  compared  with  those  of  the  human 
subject,  which  would  prevent  their  receiving  all  the  blood  coming 
from  the  left  ventricle ;  or  to  some  differences  in  the  manipulation 
of  these  experiments,  in  which  it  is  not  always  easy  to  imitate  ex- 
actly the  force  and  rapidity  of  the  different  currents  of  blood  in 
the  living  foetus.  The  above  results,  however,  are  such  as  to  leave 
no  doubt  of  the  principal  fact,  viz.,  that  up  to  an  advanced  stage  of 
foetal  life,  by  far  the  greater  portion  of  the  blood  coming  from  the 
inferior  vena  cava  passes  through  the  foramen  ovale,  into  the  left 
side  of  the  heart ;  while  by  far  the  greater  portion  of  that  coming 
from  the  head  and  upper  extremities  passes  into  the  right  side  of 
the  heart,  and  thence  outward  by  the  pulmonary  trunk  and  ductus 
arteriosus.  Toward  the  latter  periods  of  gestation,  this  division 
of  the  venous  currents  becomes  less  complete,  owing  to  the  three 
following  causes : — 

First,  the  lungs  increasing  in  size,  the  two  pulmonary  arteries,  as 
well  as  the  pulmonary  veins,  enlarge  in  proportion;  and  a  greater 
quantity  of  the  blood,  therefore,  coming  from  the  right  ventricle, 
instead  of  going  onward  through  the  ductus  arteriosus,  passes  to 
the  lungs,  and  returning  thence  by  the  pulmonary  veins  to  the  left 
auricle  and  ventricle,  joins  the  stream  passing  out  by  the  arch  of 
the  aorta. 

Secondly,  the  Eustachian  valve  diminishes  in  size.  This  valve, 
which  is  very  large  and  distinct  at  the  end  of  the  sixth  month 
(Fig.  271),  subsequently  becomes  atrophied  to  such  an  extent  that, 
at  the  end  of  gestation,  it  has  altogether  disappeared,  or  is  at  least 
reduced  to  the  condition  of  a  very  narrow,  almost  imperceptible 


684      DEVELOPMENT    OF    THE    CIRCULATORY    APPARATUS. 

membranous  ridge,  which  can  exert  no  influence  on  the  direction 
of  the  current  of  blood  passing  by  it.  Thus,  the  cavity  of  the  infe- 
rior vena  cava,  at  its  upper  extremity,  ceases  to  be  separated  from 
that  of  the  right  auricle ;  and  a  passage  of  blood  from  one  to  the 
other  may,  therefore,  more  readily  take  place. 

Thirdly,  the  foramen  ovale  becomes  partially  closed  by  a  valve 
which  passes  across  its  orifice  from  behind  forward.  This  valve, 
which  begins  to  be  formed  at  a  very  early  period,  is  called  the 
valve  of  the  foramen  ovale.  It  consists  of  a  thin,  fibrous  sheet,  which 
grows  from  the  posterior  surface  of  the  auricular  cavity,  just  to  the 
left  of  the  foramen  ovale,  and  projects  into  the  left  auricle,  its  free 
edge  presenting  a  thin  crescentic  border,  and  being  attached,  by  its 
two  extremities,  to  the  auricular  septum  upon  the  left  side.  This 
valve  does  not  at  first  interfere  at  all  with  the  flow  of  blood  from 
right  to  left,  since  its  edge  hangs  freely  and  loosely  into  the  cavity 
of  the  left  auricle.  It  only  opposes,  therefore,  during  the  early 
periods,  any  accidental  regurgitation  from  left  to  right. 

But  as  gestation  advances,  while  the  walls  of  the  heart  con- 
tinue to  enlarge,  and  its  cavities  to  expand  in  every  direction,  the 
fibrous  bundles,  forming  the  valve,  do  not  elongate  in  proportion* 
The  valve,  accordingly,  becomes  drawn  downward  more  and  more 
toward  the  foramen  ovale.  It  thus  comes  in  contact  with  the  edges 
of  the  interauricular  septum,  and  unites  with  its  substance ;  the 
adhesion  taking  place  first  at  the  lower  and  posterior  portion,  and 
proceeding  gradually  upward  and  forward,  so  as  to  make  the  pas- 
sage, from  the  right  auricle  to  the  left,  more  and  more  oblique  in 
direction. 

At  the  same  time,  an  alteration  takes  place  in  the  position  of  the 
inferior  vena  cava.  This  vessel,  which  at  first  looked  transversely 
toward  the  foramen  ovale,  becomes  directed  more  obliquely  for- 
ward ;  so  that,  the  Eustachian  valve  having  mostly  disappeared,  a 
part  of  the  blood  of  the  inferior  vena  cava  enters  the  right  auricle, 
while  the  remainder  still  passes  through  the  equally  oblique  open  • 
ing  of  the  foramen  ovale. 

At  the  period  of  birth  a  change  takes  place,  by  which  the 
foramen  ovale  is  completely  occluded,  and  all  the  blood  coming 
through  the  inferior  vena  cava  is  turned  into  the  right  auricle. 

This  change  depends  upon  the  commencement  of  respiration. 
A  much  larger  quantity  of  blood  than  before  is  then  sent  to  the 
lungs,  and  of  course  returns  from  them  to  the  left  auricle.  The 
left  auricle,  being  then  completely  filled  with  the  pulmonary  blood, 


DEVELOPMENT    OF    THE    HEART. 


685 


no  longer  admits  a  free  access  from  the  rigtit  auricle  througli  the 
foramen  ovale ;  and  the  valve  of  the  foramen,  pressed  backward 
more  closely  against  the  edges  of  the  septum,  becomes  after  a  time 
adherent  throughout,  and  obliterates  the  opening  altogether.  The 
cutting  off  of  the  placental  circulation  diminishes  at  the  same  time 
the  quantity  of  blood  arriving  at  the  heart  by  the  inferior  vena 
cava.  It  is  evident,  indeed,  that  the  same  quantity  of  blood  which 
previously  returned  from  the  placenta  by  the  inferior  cava,  on  the 
right  side  of  the  auricular  septum,  now  returns  from  the  lungs,  by 
the  pulmonary  veins  upon  the  left  side  of  the  same  septum ;  and  it 
is  owing  to  all  these  circumstances  combined,  that  while  before  birth 
a  portion  of  the  blood  always  passed  from  the  right  auricle  to  the 
left  through  the  foramen  ovale,  no  such  passage  takes  place  after 
birth,  since  the  pressure  is  then  equal  on  both  sides  of  the  auricular 
septum. 

The  foetal  circulation,  represented  in  Fig.  272,  is  then  replaced 
by  the  adult  circulation,  represented  in  Fig.  273. 


Fig.  273. 


Diagram  nf  A  ntJLT  Cir  crLATtoN  throttoh  thr  Hbabt.— ffl,  ^..  Superior  and  inferior  vpna 
CAvm.  h.  Bixht  ventricle,  c.  Pulmonary  artery,  dividing  into  right  and  left  branches,  d.  Pulmo- 
nary vein.    e.  Left  ventricle.    /.  Aorta. 

That  portion  of  the  septum  of  the  auricles,  originally  occupied 
by  the  foramen  ovale,  is  accordingly  constituted,  in  the  adult  con 
dition,  by  the  valve  of  the  foramen  ovale,  which  has  become  adhe- 


686      DEVELOPMENT    OF    THE    CIECULATORY    APPARATUS. 

rent  to  the  edges  of  the  septum.  The  auricular  septum  in  the  adult 
heart  is,  therefore,  thinner  at  this  spot  than  elsewhere ;  and  presents, 
on  the  side  of  the  right  auricle,  an  oval  depression,  termed  the /055a 
ovalis,  which  indicates  the  site  of  the  original  foramen  ovale.  The 
fossa  ovalis  is  surrounded  by  a  slightly  raised  ring,  the  annulus 
ovalis,  representing  the  curvilinear  edge  of  the  original  auricular 
septum. 

The  foramen  ovale  is  sometimes  completely  obliterated  within  a 
few  days  after  birth.  It  often,  however,  remains  partially  pervious 
for  several  weeks  or  months.  We  have  a  specimen,  taken  from  a 
child  of  one  year  and  nine  months,  in  which  the  opening  is  still 
very  distinct;  and  it  is  not  unfrequent  to  find  a  small  aperture 
existing  even  in  adult  life.  In  these  instances,  however,  although 
the  adhesion  and  solidification  of  the  auricular  septum  may  not  be 
complete,  yet  no  disturbance  of  the  circulation  results,  and  no  ad- 
mixture of  blood  takes  place  between  the  right  and  left  sides  of  the 
heart ;  since  the  passage  through  the  auricular  septum  is  always 
very  oblique  in  its  direction,  and  its  valvular  arrangement  prevents 
any  regurgitation  from  left  to  right,  while  the  complete  filling  of 
the  left  auricle  with  pulmonary  blood,  as  above  mentioned,  equally 
opposes  any  passage  from  right  to  left. 


DEVELOPMENT    OF    THE    BODY   AFTEE    BIRTH.  667 


CHAPTER     XVIII. 

DEYELOPMENT    OF   THE    BODY   AFTER    BIETH. 

The  newlj-born  infant  is  still  very  far  from  having  arrived  ai  a 
state  of  complete  development.  The  changes  through  which  it  has 
passed  during  intra-uterine  life  are  not  more  marked  than  those 
which  are  to  follow  during  the  periods  of  infancy,  childhood,  and 
adolescence.  The  anatomy  of  the  organs,  both  internal  and  ex- 
ternal, their  physiological  functions,  and  even  the  morbid  derange- 
ments to  which  they  are  subject,  continue  to  undergo  gradual  and 
progressive  alterations,  throughout  the  entire  course  of  subsequent 
life.  The  history  of  development  extends,  properly  speaking,  from 
the  earliest  organization  of  the  embryonic  tissues  to  the  complete 
formation  of  the  adult  body.  The  period  of  birth,  accordingly, 
marks  only  a  single  epoch  in  a  constant  series  of  changes,  some  of 
which  have  preceded,  while  many  others  are  to  follow. 

The  weight  of  the  newly-born  infant  is  a  little  over  six  pounds. 
The  middle  point  of  the  body  is  nearly  at  the  umbilicus,  the  head 
and  upper  extremities  being  still  very  large,  in  proportion  to  the 
lower  extremities  and  pelvis.  The  abdomen  is  larger  and  the 
chest  smaller,  in  proportion,  than  in  the  adult.  The  lower  extremi- 
ties are  curved  inward,  as  in  the  foetal  condition,  so  that  the  soles  of 
the  feet  look  obliquely  toward  each  other,  instead  of  being  directed 
horizontally  downward,  as  at  a  subsequent  period.  Both  upper 
and  lower  extremities  are  habitually  curled  upward  and  forward 
over  the  chest  and  abdomen,  and  all  the  joints  are  constantly  in  a 
semi-flexed  position. 

The  process  of  respiration  is  very  imperfectly  performed  for 
some  time  after  birth.  The  expansion  of  the  pulmonary  vesicles, 
and  the  changes  in  the  circulatory  apparatus  described  in  the  pre- 
ceding chapter,  far  from  being  sudden  and  instantaneous,  are 
always  more  or  less  gradual  in  their  character,  and  require  an 
interval  of  several  days  for  their  completion.     Eespiration,  indeed 


688  DEVELOPMENT   OF    THE    BODY   AFTER   BIRTF. 

seems  to  be  accomplislied,  during  this  period,  to  a  considerable 
extent  through  the  skin,  which  is  remarkably  soft,  vascular,  and 
ruddy  in  color.  The  animal  heat  is  also  less  actively  generated 
than  in  the  adult,  and  requires  to  be  sustained  by  careful  protec- 
tion, and  by  contact  with  the  body  of  the  mother.  The  young 
infant  sleeps  during  the  greater  part  of  the  time ;  and  even  when 
awake  there  are  but  few  manifestations  of  intelligence  or  percep- 
tion. The  special  senses  of  sight  and  hearing  are  dull  and  inex- 
citable,  though  their  organs  are  perfectly  formed;  and  even 
consciousness  seems  present  only  to  a  very  limited  extent.  Volun- 
tary motion  and  sensation  are  nearly  absent ;  and  the  almost  con- 
stant irregular  movements  of  the  limbs,  observable  at  this  time, 
are  evidently  of  a  reflex  or  automatic  character.  Nearly  all  the 
nervous  phenomena,  indeed,  presented  by  the  newly-born  infant, 
are  of  a  similar  nature.  The  motions  of  its  hands  and  feet,  the  act 
of  suckling,  and  even  its  cries  and  the  contortions  of  its  face,  are 
reflex  in  their  origin,  and  do  not  indicate  the  existence  of  any 
active  volition,  or  any  distinct  perception  of  external'  objects. 
There  is  at  first  but  little  nervous  connection  established  with  the 
external  world,  and  the  system  is  as  yet  almost  exclusively  occu- 
pied with  the  functions  of  nutrition  and  respiration. 

This  preponderance  of  the  simple  reflex  actions  in  the  nervous 
system  of  the  infant,  is  observable  even  in  the  diseases  to  which  it 
is  peculiarly  subject  for  some  years  after  birth.  It  is  at  this  age 
that  convulsions  from  indigestion  are  of  most  frequent  occurrence, 
and  even  temporary  strabismus  and  paralysis,  resulting  from  the 
same  cause.  It  is  well  known  to  physicians,  moreover,  that  the 
effect  of  various  drugs  upon  the  infant  is  very  different  from  that 
which  they  exert  upon  the  adult.  Opium,  for  example,  is  very 
much  more  active,  in  proportion  to  the  dose,  in  the  infant  than  in 
the  adult.  Mercury,  on  the  other  hand,  produces  salivation  with 
greater  difficulty  in  the  former  than  in  the  latter.  Blisters  excite 
more  constitutional  irritation  in  the  young  than  in  the  old  subject ; 
and  antimony,  when  given  to  children,  is  proverbially  uncertain 
and  dangerous  in  its  operation. 

The  difference  in  the  anatomy  of  the  newly -born  infant,  and  that 
of  the  adult,  may  be  represented,  to  a  certain  extent,  by  the  fol- 
lowing list,  which  gives  the  relative  weight  of  the  most  important 
internal  organs  at  the  period  of  birth  and  that  of  adult  age ;  the 
weight  of  the  entire  body  being  reckoned,  in  each  case,  as  1000. 
The  relative  weight  of  the  adult  organs  has  been  calculated  from 


DEVELOPMENT    OF    THE    BODY    AFTER    BIRTH.  689 

tte  estimates  of  Cruveilheir,  Solly,  Wilson,  &c. ;  that  of  the  organs 
in  the  fcetus  at  term  from  our  own  observations. 


We 


FffiTus  AT  Teem. 

ABCLT. 

gilt  of  tlie  entire  body 

.       1000.00 

1000.00 

'        " 

encephalon 

148.00 

23.00 

I          a 

liver  . 

37.00 

29.00 

i          li 

heart 

7.77 

4.17 

I          ii 

kidneys 

6.00 

4.00 

i           e: 

renal  capsules    o 

1.63 

0.13 

i           u 

thyroid  gland     . 

0.60 

0.51 

I          11 

thymus  gland     « 

3.00 

0.00 

It  will  be  observed  that  most  of  the  internal  organs  diminish  in 
relative  size  after  birth,  owing  principally  to  the  increased  develop- 
ment of  the  osseous  and  muscular  systems,  both  of  which  are  in  a 
very  imperfect  condition  throughout  intra-uterine  lifa  but  which 
come  into  activity  during  childhood  and  youth. 

Within  the  first  day  after  birth  the  remains  of  the  umbilical 
cord  begin  to  wither,  and  become  completely  desiccated  by  about 
the  third  day.  A  superficial  ulceration  then  takes  place  about  the 
point  of  its  attachment,  and  it  is  separated  and  thrown  off  within 
the  first  week.  After  the  separation  of  the  cord,  the  umbilicus 
becomes  completely  cicatrized  by  the  tenth  or  twelfth  day  after 
birth.  (Gruy.) 

An  exfoliation  and  renovation  of  the  cuticle  also  take  place 
over  the  whole  body  soon  after  birth.  According  to  Kolliker,  the 
eyelashes,  and  probably  all  the  hairs  of  the  body  and  head  are 
thrown  off  and  replaced  by  new  ones  within  the  first  year. 

The  teeth  in  the  newly-born  infant  are  but  partially  developed, 
and  are  still  inclosed  in  their  follicles,  and  concealed  beneath  the 
gums.  They  are  twenty  in  number,  viz.,  two  incisors,  one  canine, 
and  two  molars,  on  each  side  of  each  jaw.  At  birth  there  is  a  thin 
layer  of  dentine  and  enamel  covering  their  upper  surfaces,  but 
the  body  of  the  tooth  and  its  fangs  are  formed  subsequently  by 
progressive  elongation  and  ossification  of  the  tooth-pulp.  The 
fully-formed  teeth  emerge  from  the  gums  in  the  following  order. 
The  central  incisors  in  the  seventh  month  after  birth;  the  lateral 
incisors  in  the  eighth  month ;  the  anterior  molars  at  the  end  of  the 
first  year;  the  canines  at  a  year  and  a  half;  and  the  second  molars 
at  two  years  (Kolliker).  The  eruption  of  the  teeth  in  the  lower 
jaw  geuerally  precedes  by  a  short  time  that  of  the  corresponding 
teeth  in  the  upper. 

During  the  seventh  year  a  change  begins  to  take  place  by  which 
44 


690  DEVELOPMENT    OF    THE    BODY    AFTEE    BIRTH. 

the  first  set  of  teeth  are  thrown  off  and  replaced  by  a  second  or 
permanent  set,  differing  in  number,  size,  and  shape  from  those 
which  preceded.  The  anterior  permanent  molar  first  shows  itself 
just  behind  the  posterior  temporary  molar,  on  each  side.  This 
hajDpens  at  about  six  and  a  half  years  after  birth.  At  the  end  of 
the  seventh  year  the  middle  incisors  are  thrown  off  and  replaced 
by  corresponding  permanent  teeth,  of  larger  size.  At  the  eighth 
year  a  similar  exchange  takes  place  in  the  lateral  incisors.  In  the 
ninth  and  tenth  years,  the  anterior  and  second  molars  are  replaced 
by  the  anterior  and  second  permanent  bicuspids.  In  the'  twelfth 
year,  the  canine  teeth  are  changed.  In  the  thirteenth  year,  the 
second  permanent  molars  show  themselves ;  and  from  the  seven- 
teenth to  the  twenty-first  year,  the  third  molars,  or  "  wisdom  teeth," 
emerge  from  the  gums,  at  the  posterior  extremities  of  the  dental 
arch.  (Wilson.)  The  jaw,  therefore,  in  the  adult  condition,  contains 
three  teeth  on  each  side  more  than  in  childhood,  making  in  all 
thirty-two  permanent  teeth ;  viz.,  on  each  side,  above  and  below, 
two  incisors,  one  canine,  two  bicuspids,  and  three  permanent 
molars. 

The  entire  generative  apparatus,  which  is  still  altogether  inactive 
at  birth,  begins  to  enter  upon  a  condition  of  functional  activity 
from  the  fifteenth  to  the  twentieth  year.  The  entire  configuration 
of  the  body  alters  in  a  striking  manner  at  this  period,  and  the  dis- 
tinction between  the  sexes  becomes  more  complete  and  well 
marked.  The  beard  is  developed  in  the  male ;  and  in  the  female 
the  breasts  assume  the  size  and  form  characteristic  of  the  condition 
of  puberty.  The  voice,  which  is  shrill  and  sharp  in  infancy  and 
childhood,  becomes  cleejDer  in  tone,  and  the  countenance  assumes  a 
more  sedate  and  serious  expression.  After  this  period,  the  mus- 
cular system  increases  still  further  in  size  and  strength,  and  the 
consolidation  of  the  skeleton  also  continues ;  the  bony  union  of  its 
various  parts  not  being  entirely  accomplished  until  the  twenty-fifth 
or  thirtieth  year.  Finally,  all  the  different  organs  of  the  body 
arrive  at  the  adult  condition,  and  the  entire  process  of  development 
is  then  complete. 


ODEX. 


Absorbent  glands,  168,  317 

vessels,  167,  317 
Absorption,  162 

by  bloodvessels,  165 

by  lacteals,  168 

of  fat,  171 

of  different  liquids  by  animal  sub- 
stances, 312 

of  oxygen  in  respiration,  243 

by  egg  during  incubation,  606 

of  calcareous  matter   by  allantois, 
606 
Acid,  carbonic,  242,  246 

lactic,  in  gastric  juice,  139 

in  souring  milk,  99,  336 

glyko-cliolic,  180 

tauro-cholic,  181 

pneumic,  247 
.  -uric,  347,  354 

oxalic  in  urine,  360 
Acid  fermentation  of  urine,  360 
Acidity  of  gastric  juice,  cause  of,  139 

of  urine,  353 
Acini,  of  liver,  338 
Adipose  vesicles,  90 

digestion  of,  158,  159 
Adult  circulation,  670 

establishment  of,  685 
Aerial  respiration,  233 
Age,  influence  of,  on  exhalation  of  car- 
bonic acid,  250 

on  comparative  weight   of  organs, 
689 
Air,  quantity  of,  used  in  respiration,  238 

alterations  of,  in  respiration,  241 

circulation  of,  in  lungs,  239 
Air-cells  of  lungs,  235 
Air-chamber,  in  fowl's  egg,  552 
Albumen,  100 

of  the  blood,  224 

in  milk,  335 

of  the  egg,  how  produced,  550 

its  liquefaction  and  absorption  dur- 
ing development  of  foetus,  602- 
604 
Albuminoid  substances,  95 

digestion  of,  141 
Albuminose,  142 

interference   with   Trommer's    test, 
143 

with  action  of   iodine  and   starch, 
144 


Alimentary  canal  in  different  animals, 
116,  119 

development  of,  644 
Alkalies,  effect  of,  on  urine,  354 
Alkaline  chlorides,  71-74 

phosphates,  77 

carbonates,  76,  77 
Alkaline  fermentation  of  urine,  360 
Alkalescence  of  blood,  due  to  carbonates, 

76 
Allantois,  599 

formation  of,  601 

in  fowl's  egg,  604 

function  of,  605 

in  foBtal  pig,  622 
Alligator,  brain  of,  382 
Amnion,  509 

formation  of,  600 

enlargement  of,  during  latter  part  of 
pregnancy,  630 

contact  with  chorion,  631 
Amniotic  folds,  600 
Amniotic  fluid,  630 

its  use,  631 

contains  sugar  at  a  certain  period, 
648 
Amniotic  umbilicus,  600 
Analysis,  of  animal  fluids,  64,  65 

of  milk,  112,  334 

of  wheat  flour,  112 

of  oatmeal,  112 

of  eggs,  113 

of  meat,  113 

of  saliva,  124,  126 

of  gastric  juice,  139 

of  pancreatic  juice,  155 

of  bile,  176 

of  blood-globules,  218 

of  blood-plasma,  223 

of  mucus,  328 

of  sebaceous  matter,  329 

of  perspiration,  331 

of  butter,  336 

of  urine,  352 

of  fluid  of  thoracic  duct,  318 

of  chyle  and  lymph,  320 
Andrai,  and   Gavari{et,  production   of 

carbonic  acid  in  respiration,  250 
Animal  functions,  59 
Animal  heat,  253-263 

in  different  species,  255 

mode  of  generation,  257 

(  691  ) 


692 


INDEX. 


Animal  lieat  influenced  by  local  causes, 
261 

in  different  organs,  262 

increase  of,  after  section  of  sympa- 
thetic nerve,  521 
Animal  and  vegetable  parasites,  532 
Animalcules,  infusorial,  529 

mode  of  production,  530 
Annulus  ovalis,  686 
Anterior  columns  of  spinal  cord,  380 

their  excitability,  402 
Aorta,  development  of,  670 
AiJlysia,  nervous  system  of,  375 
Appetite,  disturbed  by  anxiety,  &c.,  149 

necessary  to  digestion  of  food,  149 
Aquatic  respiration,  233 
Arch  of  aorta,  formation  of,  671 
Arches,  cervical,  670 

transformation  of,  671 
Area  pellucida,  590 

vasculosa,  603,  666 
Arteries,  281 

motion  of  blood  in,  282 

pulsation  of,  283-285 

elasticity  of,  281,  286 

rapidity  of  circulation  in,  289 

omphalo-meseuteric,  666 

vertebral,  669 

umbilical,  669 
Arterial  pressure,  287 
Arterial  system,  development  of,  669-672 
Articulata,  nervous  system  of,  376 

reflex  action  in,  377 
Articulation  of  tapeworm,  541 
Arytenoid  cartilages,  240 

movements  of,  241 
Assimilation,  324 

destructive,  341 
Auditory  apparatus,  505 

nerves,  447,  507 
Auricle,  single,  of  fish,  265 

double,  of  reptiles,  birds,  and  mam- 
malians, 266,  267 

contraction  of,  279 
Auriculo-ventricular  valves,  action  of, 

269 
Axis-cylinder,  of  nervous  filaments,  370 
Aztec  children,  426 
Azygous  veins,  formation  of,  673 

Beaumont,  Dr.,  experiments  on  Alexis  St. 

Martin,  135-146 
Bernaed,  on  the  difi"erent  kinds  of  saliva, 
125 
on  efi'ect  of  dividing  Steno's  duct, 

131 
on  digestion  of  fat  in  intestine,  155 
on  formation  of  liver-sugar,  200, 202, 

203 
on  decomposition  of  bicarbonates  in 

lung,  247 
on  temperature  of  blood  in  diff'erent 
organs,  262 


BiPDEE  AND  Schmidt,  on  daily  quantity 
of  bile,  188 

on  effect  of  excluding  bile  from  in- 
testine, 195 

on  reabsorption  of  bile,  196 
Bile,  175 

composition  of,  176 

tests  for,  184 

daily  quantity  of,  188 

functions  of,  193 

reaction  with  gastric  juice,  193 

reabsorption,  196 

mode  of  secretion,  337 
Biliary  salts,  177 

of  human  bile,  183 
Biliverdine,  103,  176 

tests  for,  184 

passage  into  the  urine,  357 
Blastodermic  membrane,  688 
Blood,  213 

red  globules  of,  214 

white  globules,  220 

plasma,  223 

coagulation  of,  225 

buffy  coat,  230 

entire  quantity  of,  231 

alterations  of,  in  respiration,  243 

temperature  of,  254 

in  difl"erent  organs,  262 

circulation  of,  264 

through  the  heart,  270 
through  the  arteries,  282 
through  the  veins,  290 
through  the  capillaries,  296 
BoussiNGAULT,  on  chloride  of  sodium  in 
food,  73 

on  internal  production  of  fat,  93 
Brain,  381,  417 

of  alligator,  382 

of  rabbit,  383 

human,  386,  417 

remarkable  cases  of  injury  to,  419, 
420 

size  of,  in  different  races,  423,  424 
in  idiots,  425 

development  of,  638,  639 
Branchige,  232 

of  meno-branchus,  233 
Broad  ligaments,  formation  of,  662 
Bronchi,  division  of,  234,  235 

ciliary,  motion  in,  239 
Brunner's  glands,  152 
Buffy  coat  of  the  blood,  230 
Butter,  335 

composition  of,  336 

condition  in  milk,  91,  335 
Butyrine,  336 

Canals  of  Cuvier,  672 
Capillaries,  295 

their  inosculation,  296 

motion  of  blood  in,  297 
Capillary  circulation,  296 


INDEX. 


693 


Capillary  circulation,  causes  of,  298 
rapidity  of,  301,  302 
peculiarities  of,  iu  different  parts, 
303 
Caput  coli,  formation  of,  645 
Carbonic  acid,  in  the  breath,  242 

proportion  of,   to  oxygen  absorbed, 

242,  243 
in  the  blood,  243 
origin  of,  in  lungs,  247 
in  the  blood,  248 
in  the  tissues,  248 
mode  of  production,  248 
daily  quantity  of,  250 
variations  of,  250 
exhaled  by  skin,  252 

by  egg,  during  incubation,  606 
absorbed  by  vegetables,  260 
Carbonate  of  lime,  76 
of  soda,  76 
of  potassa,  77 

of  ammonia,   in   putrefying   urine, 
360 
*Cardiac  circulation,  in  foetus,  682 

in  adult,  685 
Carnivorous  animals,  respiration  of,  50, 
243 
urine  of,  345 
Cartilagine,  102 
Caseine,  100 
Cat,  secretion  of  bile  in,  188 

closure  of  eyelids,  after  division  of 
sympathetic,  522 
Catalytic  action,  98 
of  pepsin,  142 
Centipede,  nervous  system  of,  376 
Centre,  nervous  definition  of,  373 
Cerebrum,  419.     See  Hemispheres. 
Cerebral    ganglia,    382.      See    Hemi- 
spheres. 
Cerebellum,  429 

effects  of  injury  to,  431 
removal  of,  431-434 
function  of,  430 
development  of,  638,  639 
Cerebro-spinal  system,  378,  379 

development  of,  637 
Cervix  uteri,  554 
in  foetus,  663 
Cervical  arches,  670 

transformation  of,  671 
Changes,  in  egg,  while  passing  through 
oviduct,  548,  551 
in  hepatic  circulation  at  birth,  677 
in  comparative  size  of  organs,  after 
birth,  689 
Chevreuil,  experiments  on   imbibition, 

312 
Chick,  development  of,  602-607 
Children,  Aztec,  426 
Chloride  of  sodium,  71 

its  proportion  in  the  animal  tissues 
and  Huids,  72 


Chloride  of  sodium,  importance  of,  in  the 
food,  73 

mode  of  discharge  from  the  body,  74 

partial  decomposition  of,  in  the  body, 
74 
Chloride  of  potassium,  74 
Cholesterin,  176 
Chorda  dorsalis,  591 
Chorda  tympani,  488 
Chordje  vocales,  movement  of,  in  respi- 
ration, 240 

action  of,  in  the  production  of  vocal 
sounds,  464 

obstruction  of  glottis  by,  after  divi- 
sion of  pneumogastric,  466,  467 
Chorion,  formation  of,  608 

villosities  of,  610 

source  of  vascularity  of,  611 

union  with  decidua,  619 
Chyle,  153,  169,  320 

in  lacteals,  170 

absorption  of,  171 

by  intestinal  epithelium,  172 

in  blood,  173 
Ciliary  motion,  in  bronchi,  221 

in  Fallopian  tubes,  573 
Ciliary  nerves,  514 
Circulation,  264 

in  the  heart,  270 

in  the  arteries,  282 

in  the  veins,  290 

in  the  capillaries,  297 

rapidity  of,  302 

peculiarities  of,  in  different  parts, 
304 

in  liver,  339 

in  placenta,  621-629 
Circulatory  apparatus,  development  of, 

665-686 
Civilization,   aptitude    for,   of    different 

races,  424 
Classification  of  cranial  nerves,  448 
Clot,  formation  of,  225 

separation  from  serum,  226 

buffed  and  cupped,  230 
Coagulation,  98 

of  fibrin,  223 

of  blood,  225 

of  white  substance  of  Schwann,  in 
nerve-fibres,  369 
Colin,  on  unilateral  mastication,  127 
Cold,  resistance  to,  by  animals,  253 

effect  of,  when  long  continued,  254 
Colostrum,  333 
Coloring  matters,  102 

of  blood,  102,  218 

of  the  skin,  103 

of  bile,  103 

of  urine,  103 
Commissure,  of  spinal  cord,  gray,  381 

white,  381 

transverse,  of  cerebrum,  387 

of  cerebellum,  387 


694 


INDEX. 


Commissures,  nervous,  373 

olfactory,  382,418 
Congestion,  of  ear,  &c.,  after  division  of 

sympathetic,  521 
Convolvulus,  sexual  apparatus  of,  540 
Consentaneous  action  of  muscles,  430 
Contact,  of  cliorion  and  amnion,  631 

of  decidua  vera  and  reflesa,  632 
Contraction,  of  stomacli   during   diges- 
tion, 145 

of  spleen,  208 

of  blood-clot,  226 

of  diaphragm  and  intercostal  mus- 
cles, 236 

of  posterior  crico-arytenoid  muscles, 
241 

of  ventricles,  275 

of  muscles  after  death,  389 

of  sphincter  ani,  414 

of  rectum,  414 

of  urinary  bladder,  415 

of  pui)il,  under  influence  of  light, 
367,  435,  501 
after  division   of  sympathetic, 
522 
Cooking,  effect  of,  on  food,  114 
Cord,  spinal,  379,  398 

umbilical,  631 

withering  and  separation  of,  689 
Cori^us  callosum,  387 
Corpus  luteum,  576 

of  menstruation,  576-580 

of  pregnancy,  580-585 

three  weeks  after  menstruation,  578 

four  weeks  after  menstruation,  579 

nine  weeks  after  menstruation,  579 

at  end  of  second   month   of  preg- 
nancy, 582 

at  end  of  fourth  month,  582 

at  term,  583 

disappearance  of,  after  delivery,  584 
Corpora  Malpighiana,  of  spleen,  191 
Corpora  striata,  383,  419 
Corpora  olivaria,  384 
Corpora  Wolffiana,  655 
CosTE,  onr  rupture  of  Graafian  follicle  in 

menstruation,  572,  573 
Cranial  nerves,  446 

classification  of,  448 

motor,  449 

sensitive,  449,  450 
Creatine,  346 
Creatinine,  346 
Cremaster  muscle,  formation  of,  659 

function  of,  in  lower  animals,  660 
Crystals,  of  stearine,  87 

and  margarine,  88 

of  cholesterin,  177 

of  glyko-cholate  of  soda,  178 

of  biliary  matters  of  dog's  bile,  182 

of  urea,  343 

of  creatine,  346 

of  creatinine.  346 


Crystals,  of  urate  of  soda,  347 
of  uric  acid,  354 
of  oxalate  of  lime,  360 
of  triple  phosphate,  362 
C'rystallizable  sustances  of  organic  ori- 

gin,  79 
Crossing  of  fibres  in  medulla  oblongata, 
385,  404 
of  sensitive   fibres  in  spinal   cord, 

405 
of  fibres  of  optic  nerves,  436,  437 
of  streams  of  blood  in  foetal  heart, 
681,  682 
Ckuikshank,  rupture  of  Graafian  follicle 

in  menstruation,  572 
Cumulus  proligerus,  567 
Cutaneous  respiration,  252 

perspiration,  330 
Cuticle,  exfoliation  of,  during  foetal  life, 
643 
after  birth,  689 
Cysticercus,  537 

transformation  of  into  taenia,  538 
production  of,  from  CEtgs  of  taenia,  ■ 
539 

Death,  a  necessary  consequence  of  life, 

526 
Decidua,  614 
vera,  616 
reflexa,  618 

union  with  chorion,  619 
its  discharge  in  cases  of  abortion, 
618 
at  the  time  of  delivery,  633 
Decussation  of  anterior  columns  of  spinal 
cord,  385,  404 
of  optic  nerves,  436,  437 
Degeneration,  fatty,  of  muscular  fibres 

of  uterus,  after  delivery,  635 
Deglutition,  133 

retarded  by  division  of  Steno's  duct, 
131 
by  division  of  pneumogastric, 
463 
Dentition,  first,  689 

second,  690 
Descent  of  the  testicles,  658 

of  the  ovaries,  661 
Destructive  assimilation,  341 
Development  of  the  impregnated  egg,  586 
of  allantois,  601 
of  chorion,  608 

of  villosities  of  chorion,  610,  611 
of  decidua,  615,  616 
of  i^lacenta,  621-626 
of  nervous  system,  637 
of  eye,  640 
of  ear,  641 
of  skeleton,  641 
of  limbs,  642 
of  integument,  643 
of  alimentary  canal,  464,  646 


INDEX. 


695 


Development  of  urinary  passages,  646 

of  liver,  649,  673 

of  pliaryux  and  CESophagus,  650 

of  face,  651 

of  Wolffian  bodies,  655 

of  kidneys,  656 

of  internal  generative  organs,  657 

of  circulatory  apparatus,  665 

of  arterial  system,  669 

of  venous  system,  672 

of  hepatic  circulation,  675 

of  lieart,  678 

of  the  body  after  birth,  687 
Diabetes,  357 

in  foetus,  649 
Diaphragm,  action  of  in  breathing,  237 

formation  of,  651 
Diaphragmatic  hernia,  651 
Diet,  influence  of  on  nutrition,  108 

on  products  of  respiration,  243 

on  formation  of  urea,  345 
of  urate  of  soda,  348 
Diffusion  of  gases  in  lungs,  239 
Digestion,  115 

of  starch,  150 

of  fats,  153 

of  sugar,  150 

of  organic  substances,  141 

time  required  for,  146 
Digestive  apparatus  of  fowl,  117 

of  ox, 118 

of  man,  119 
Discharge  of  eggs  from  ovary,  549 

independent  of  sexual  intercourse, 
565 

mechanism  of,  568 

during  menstruation,  572 
Discus  proligerus,  567 
Distahce  and  solidity,  application  of,  by 

the  eye,  501,  502 
Distinction   between    corpora    lutea    of 

menstruation  and  pregnancy,  585 
Diurnal  variations,  in  exhalation  of  car- 
bonic acid,  252 

in  production  of  urea,  345 

in  density  and  acidity  of  urine,  351 
Division  of  nerves,  371 

of  heart,  into  right  and  left  cavities, 
678 
DoBSON,  on  variation  in  size  of  spleen,  208 
Drapek,  John  C,  on  production  of  urea, 

345. 
Drugs,  effect  of,  on  newly  born  infant, 

688 
Ductus  arteriosus,  679,  682 

closure  of,  679,  680 

veuosus,  676 

obliteration  of,  677 
Duodenal  glands,  152 

fistula,  190 
DuTRociiKT,  on  temperature  of  plants,  256 

ou  endosmosis  of  water  with  dilTer- 
ent  liquids,  309 


Ear,  505 

muscular  apparatus  of,  506 
development  of,  641 
Earthy  phosphates,  74,  77 
in  urine,  353 

precipitated  by  addition  of  an  alkali, 
354 
Ectopia  cordis,  651 
Egg,  544 

its  contents,  545 

where  formed,  546 

of  frog,  547,  548 

of  fowl,  549 

changes  in,  while  passing  through 

the  oviduct,  549-552 
pre-existence  of,  in  ovary,  563 
development  of,  at  period  of  puberty, 

564 
periodical  ripening  and   discharge, 

565 
discharge  of,  from  Graafian  follicle, 

568 
impregnation  of,  how  accomplished, 

561 
development  of,  after  impregnation, 

586 
of  fowl,  showing  area  vasculosa,  603 
ditto,  showing  formation  of  allantois, 

604 
of  fish,  showing  vitelline  circulation, 

666 
attachment   of,  to  uterine  mucous 

membrane,  617 
discharge  of  from  uterus,  at  the  time 

of  delivery,  633 
condition  of  in  newly  born  infant,  663 
Elasticity,  of  spleen,  208 

of  red  globules  of  blood,  216 
of  lungs,  235,  237 
of  costal  cartilages,  237 
of  vocal  cords,  241 
of  arteries,  281 
Electrical  current,  effect  of  on  muscles, 
389 
on  nerve,  391 
difierent  efi'ects  of  direct  and  inverse, 

394 
Electrical  fishes,  phenomena  of,  396 
Electricity,  no  manifestations  of  in  irri- 
tated nerve,  397 
Elevation  of  temperature,  after  division 

of  sympathetic,  261,  521 
Elongation  of  heart  in  pulsation,  275 

anatomical  causes  of,  276 
Embryo,  formation  of,  586 
Embryonic  spot,  590 
Encephalon,  381,  417 

ganglia  of,  386 
Endosmosis,  307 

of  fatty  substances,  171 
in  capillary  circulation,  314 
conditions  of,  308 
cause  of,  311 


696 


INDEX. 


Endosmosis  of  iodide  of  potassium,  313 

of  atropine,  313 

of  nux  vomica,  314 
Endosmometer,  308 

Enlargement   of  amnion,  during    preg- 
nancy, 630,  631 
Entozoa,  encysted,  534 

mode  of  production,  536 
Epithelium,  in  saliva,  124 

of  gastric  follicles,  134 

of  intestine,  during  digestion,  172 
Epidermis,  exfoliation  of,  in  foetal  life,  643 

after  birth,  689 
Epididymis,  659 
Excretine,  160 
Excretion,  341 

nature  of,  342 

importance  to  life,  342 

products  of,  343 

by  placenta,  628 
Excrementitious  substances,  342 

mode  of  formation  of,  342 

effect  of  retention  of,  342 
Exfoliation  of  cuticle,  during  fcetal  life, 
643 

after  birtli,  689 
Exhalation,  307 

of  watery  vapor,  71 

from  the  lungs,  242 

from  the  skin,  330 

from  the  egg,  during  incubation,  606 

of  carbonic  acid,  242 

of  nitrogen,  242 

of  animal  vapor,  242 
Exhaustion,  of  muscles,  by  repeated  irri- 
tation, 390 

of  nerves,  by  ditto,  392 
Exosmosis,  308 
Expiration,  movements  of,  237 

after  section  of  pneumogastric,  469 
Extractive  matters  of  the  blood,  225 
Eye,  protection  of,  by  movements  of  pu- 
pil, 367,  435,  501,  518 

by  two  sets  of  muscles,  519 
Eyeball,  inflammation  of,  after  division 

of  5th  pair,  455 
Eyelids,  formation  of,  641 

Pace,  sensitive  nerve  of,  451 

motor  nerve,  456 

development  of,  651 
Facial  nerve,  456 

sensibility  of,  459 

influence  of,  on  muscular  apparatus 
of  eye,  457 

of  nose,  458 

of  ear,  459 

paralysis  of,  458,  459 
Fallopian  tubes,  553 

formation  of,  661 
Farinaceous  substances,  79 

in  food,  80,  106 

digestion  of,  150 


Fat,  decomposition  of,  in  the  blood,  166, 

173 
Fats,  86 

proportion  of,  in  diiFerent  kinds  of 

food,  88 
condition,  in  the  various  tissues  and 

fluids,  88 
internal  source  of,  93 
decomposed  in  the  body,  94 
indispensable  as  ingredients  of  the 
food,  106 
Fatty  matters  of  the  blood,  224 
Fatty  degeneration  of  decidua,  634 

of  muscular  fibres  of  uterus,  after 
delivery,  635 
Feces,  160 

Female  generative  organs,  546 
of  frog,  547 
of  fowl,  549 
of  sow,  553 
of  human  species,  554 
development  of,  661 
Fermentation,  99 
of  sugar,  85 
acid,  of  urine,  359 
alkaline,  of  ditto,  360 
Fibrin,  100 

of  the  blood,  223 
coagulation  of,  223 
varying  quantity  of,  in  blood  of  dif- 
ferent veins,  224 
Fifth  pair  of  cranial  nerves,  451 
its  distribution,  452 
division  of,  paralyzes  sensibility  of 
face,  453 
and  of  nasal  passages,  454 
produces  iiaflammation  of  eye- 
ball, 455 
lingual  branch  of,  456 
small  root  of,  452 
Fish,  circulation  of,  247 

formation  of  umbilical  vesicle  in, 

596 
vitelline  circulation,in  embryo  of,667 
Fish,  electrical,  phenomena  of,  396 
Fissure,  longitudinal,  of  brain  and  spinal 
cord, 379 
formation  of,  640 
Fissure  of  palate,  654 
Fistula,  gastric,  Dr.  Beaumont's  case  of, 
135 
mode  of  operating  for,  136 
duodenal,  190 
Flint,  Prof.  Austin,  Jr.,  stercorine,  in 
contents  of  large  intestine,  160 
cholesterin,  in  blood  of  jugular  vein, 
177 
not  discharged  with  the  feces,  177 
effects  of  biliary  fistula,  196 
Foetal  circulation,  first  form  of,  665 

second  form  of,  667 
Follicles,  of  stomach,  134 
of  Lieberkiihn,  151 


INDEX. 


697 


Follicles,  of  Bruuner's  glands,  152 

Graafian,  546,  5ti7 

of  uterus,  554,  615 
Food,  105 

composition  of,  112 

daily  quantity  required,  113 

eti'ect  of  cooking  on,  114 
Forameu  ovale,  (380 

valve  of,  684 

closure  of,  684 
Force,  nervous,  nature  of,  395 
Formation  of  sugar  in  liver,  200 

in  foetus,  64ii 
Fossa  ovalis,  686 
Functions,  animal,  59 

vegetative,  58 

of  teeth,  121 

of  saliva,  129 

of  gastric  juice,  141 

of  pancreatic  juice,  155 

of  intestinal  juices,  153 

of  bile,  193 

of  spleen,  210 

of  mucus,  328 

of  sebaceous  matter,  329 

of  perspiration,  331 

of  tke  tears,  332 

Galvanism,  action  of,  on  muscles,  389 

on  nerves,  391 
Ganglion,  of  spinal  cord,  380 

of  tuber  annulare,  438 

of  medulla  oblongata,  439 

Casserian,  451 

of  Andersch,  460 

pueumogastiic,  461 

ophthalmic,  514 

spheno-palatine,  489,  514 

submaxillary,  514 

otic,  515 

semilunar,  516 

impar,  516 
Ganglionic  system  of  nerves,  379,  514 
Ganglia,  nervous,  372 

of  radiata,  373 

of  moUusca,  375 

of  articulata,  376 

of  posterior  roots  of  spinal  nerves, 
380 

of  alligator's  brain,  382 

of  rabbit's  brain,  383 

of  medulla  oblougata,  384 

of  human  brain,  386 

of  great  sympathetic,  514 

olfactory,  382,  418 

optic,  3t52,  434 
Gases,  diffusioa  of,  in  lungs,  239 

aboor^jtion    and    exhalation   of,   by 
lungs,  244 
by  the  tissues,  248 
Gastric  follicles,  134 
Gastric  juice,  mode  of  obtaining,  137 

comjiositiou  of,  139 


Gastric  juice,  action  on  food,  141 

interference  with  Trommer's  test,  143 
interference  vrith  action   of    starch 

and  iodine,  144 
daily  quantity  of,  147 
solvent  action  of,  on  stomach,  after 
death,  149 
Gelatine,  how  produced,  64 

effect  of  feeding  animals  on,  109 
Generation,  527 

spontaneous,  527 
of  infusoria,  530 
of  parasites,  533 
of  encysted  entozoa,  535 
of  taenia,  538 
sexual,  by  germs,  540 
Germ,  nature  of,  540 
Germination,  heat  produced  in,  238 
Germinative  vesicle,  545 

disappearance  of,  in  mature  egg,  586 
Germinative  spot,  545 
Gills,  of  fish,  232 

of  menobranclius,  233 
Glands,  of  Brunner,  152 
mesenteric,  168 
vascular,  210 
Meibomian,  329 
perspiratory,  330 
action  of,  in  secretion,  324 
Glandulse  solitarise  and  agminatae,  162 
Globules,  of  blood,  213 
red,  214 

different  appearances  of,  under 

microscope,  214,  215 
mutual  adhesion  of,  215 
color,  consistency,  and  structure 

of,  216 
action  of  water  on,  217 
composition  of,  218 
size,  &c.,  in  different  animals, 
219 
white,  220 

action  of  acetic  acid  on,  221 
red  and  white,  movement  of,  in 
circulation,  297 
Globuline,  101,  218 
Glomeruli,  of  Wolffian  bodies,  656 
Glosso-pharyngeal  nerve,  459 

action  of,  in  swallowing,  460 
Glottis,  movements  of,  in  respiration,  240 
in  formation  of  voice,  464 
closure  of,  after  section  of  pneumo- 
gastrics,  467 
Glycine,  181 
Glyco-cholic  acid,  180 
Glyco-cholate  of  soda,  180 

its  crystallization,  178,  179 
Glycogenic  function  of  liver,  200 

in  foetus,  649' 
Glycogenic  matter,  204 

its  conversion  into  sugar,  204 
GossELiN,  experiments  on  imbibition  by 
cornea,  313 


698 


IXDEX. 


Graafian  follicles,  546,  567 

structure  of,  567 

rupture  of,  and  discharge  of  egg,  568 

ruptured  during  menstruation,  672 

condition  of  foettis  at  term,  663 
Gray  substance,  of  nervous  system,  372 

of  spinal  cord,  380 

of  brain,  386 

its  want  of  irritability,  417 
Great  sympathetic,  514 

anatomy  of,  515 

sensibility  and  excitability  of,  517 

connection  of,  with  special  senses, 
518 

division  of,  influence  on  animal  heat, 
521 

on  pupil  and  eyelids,  522 

reflex  actions  of,  524 
Gubernaculum  testis,  659 

function  of,  in  lower  animals,  661 
Gustatory  nerve,  452,  483 

Hammond,  Prof.  Wm.  A.,  on   efl'ects   of 
non-nitrogenous  diet,  108 

on  production  of  urea,  344 
Hsematine,  102,  218 
Hairs,  formation  of,  in  embryo,  643 
Hare-lip,  653 

Haevey,  on  motions  of  heart,  273 
Hearing,  sense  of,  505 

apparatus  of,  506 

analogy  of  with  touch,  510,  511 
Heart,  265 

of  fish,  265 

of  reptiles,  266 

of  mammalians,  267 

of  man,  268 

circulation  of  blood  through,  270 

sounds  of,  270 

movements  of,  273 

impulse,  279 

development  of,  651,  678 
Heat,  vital,  of  animals,  253 

of  plants,  256 

how  produced,  257 

increased  by  division  of  sympathetic 
nerve,  261,  521 
Hemispheres,  cerebral,  419 

remarkable  cases  of  injury  to,  419, 
420 

effect  of  removal,  on  pigeons,  421 

efi'ect  of  disease,  in  man,  422 

comparative  size  of,  in  different  races, 
423 

functions  of,  425 

development  of,  638 
Hemorrhage,  from  placenta,  in  parturi- 
tion, 633 
Hepatic  circulation,  339 

development  of,  675 
Herbivorous  animals,  respiration  of,  50, 
243 

urineof,  346,  348 


Hernia,  congenital,  diaphragmatic,  651 
umbilical,  646 
inguinal,  661 
Hippurate  of  soda,  348 
Hunger  and  thirst,  continue  after  divi- 
sion of  pneumogastric,  473 
Hydrogen,  displacement  of  gases  in  blood 
by, 245 
exhalation  of  carbonic  acid   in  an 
atmosphere  of,  249 
Hygroscopic   property    of    organic    siib- 

stances,  97 
Hypoglossal  nerve,  477 

Imbibition,  307 

of  liquids,  by  different  tissues,  312 

by  cornea,  experiments  on,  313 
Impulse,  of  heart,  279 
Infant,  newly-born,  characteristics  of,  687 
Inflammation  of  eyeball,  after  division 

of  5th  pair,  455 
Infusoria,  529 

different  kinds  of,  530 

conditions  of  their  production,  531 

Schultze's  experiment  on  generation 
of,  532 
Inguinal  hernia,  congenital,  661 
Injection  of  placental  sinuses  from  ves- 
sels of  uterus,  627 
Inorganic  substances,  as  proximate  prin- 
ciples, 69 

their  source  and  destination,  78 
Inosculation,  of  veins,  291 

of  capillaries,  296 

of  nerves,  372 
Insalivation,  123 

importance  of,  131 

function  of,  132 
Inspiration,  how  accomplished,  236 

movements  of  glottis  in,  240 
Instinct,  nature  of,  444 
Integument,  respiration  by,  252 

development  of,  643 
Intellectual  powers,  422 

in  animals,  444 
Intestine,  of  fowl,  117 

of  man,  119 

juices  of,  150 

digestion  in,  150-159 

epithelium  of,  172 

disappearance  of  bile  in,  196 

development  of,  593,  644 
Intestinal  digestion,  150 
Intestinal  juices,  151 

action  of,  on  starch,  153 
Involution  of  uterus  after  delivery,  635 
Iris,  movements  of,  367,  435,  501,  518 

after  division  of  sympathetic,  522 
Irritability,  of  gastric  mucous  membrane, 
137 

of  the  heart,  276 

of  muscles,  389 

of  nerves,  391 


INDEX. 


699 


Jackson,  Prof.  Samuel,  on  digestion  of  fat 

iu  intestine,  154 
Jaundice,  185 

yellow  color  of  urine  in,  357 

Kidneys,  peculiarity  of   circulation  in, 
305 
elimination  of  medicinal  substances 

by,  357 
formation  of,  656 
KcciiENMEiSTEK,  experiments  on  produc- 
tion of  tsenia  from  cysticercus, 
538 
of    cysticercus    from    eggs    of 
tsenia,  539 

Lachrymal  secretion,  332 

its  function,  333 
Lactation,  333 

variations  in  composition  of  milk 
during,  337 
Lacteals,  168,  170,  319 

and  lymphatics,  167,  172 
Larynx,  action  of,  in  respiration,  222 
in  formation  of  voice,  464 
nerves  of,  462,  464 
protective  action  of,  466 
movements  in  respiration,  466 
Lassaigxe,  experiments  on  saliva,  132 

analysis  of  lymph,  318 
Layers,  external  and  internal,  of  blasto- 
dermic membrane,  688 
Lead,  salts  of,  action  in  distinguishing 

the  biliary  matters,  183 
Lehmanx,  on  formation  of  carbonates  in 
blood,  76 
on  total  quantity  of  blood,  231 
on  effects  of   non-nitrogenous   diet, 
108 
Lens,  crystalline,  action  of,  495 
Leuckaet,  on  production  of  cysticercus, 

539 
LiEBiG,  on  absorption  of  different  liquids 

under  pressure,  310 
Ligament  of  the  ovary,  formation  of,  662 
Limbs,  formation  of,  in  frog,  594 
in  human  embryo,  642 
Liver,  vascularity  of,  338 
lobules  of,  338,  339 
secreting  cells,  339,  340 
formation  of  sugar  in,  200 
congestion  of,  after  feeding,  207 
development  of,  649,  675 
Liver  cells,  92,  340 

their  action  in  secretion,  340 
Liver-sugar,  formation  of,  200 
after  death,  203 
in  lVi;tus,  649 
Lobules,  of  lung,  235 
of  liver,  338,  339 
Local  production  of  carbonic  acid,  248 

of  animal  lieat,  261 
Local  variations  of  circulation,  305 


LoNGET,  on  interference   of  albuminose 
with  Trommer's  test,  143 
on  sensibility  of  glosso-pharyngeal 

nerve,  459 
on    irritability   of    anterior    spinal 
roots,  401 
LoxGET   AKD   Matteucci,  experiment  on 
signs'  of    electricity   in    an    iriitated 
nerve,  397 
Long  and  short-sightedness,  496 
Lungs,  structure  of,  in  reptiles,  234 
iu  man,  235 
alteration  of,  after  division  of  pneu- 
mogastrics,  469 
Lymph,  169,  318 

quantity  of,  320 
Lymphatic  system,  168,  317 

Magxus,  on  proportions  of  oxygen  and 

carbonic  acid  in  blood,  245 
Male  organs  of  generation,  556 

development  of,  658 
Malpighian  bodies  of  spleen,  209 
Mammalians,  circulation  in,  267 
Mammary  gland,  structure  of,  333 

secretion  of,  334 
Marcet,  on  excretine,  160 
Maeey,  M.,  experiments  on  arterial  pul- 
sation, 285 
Mastication,  121 

unilateral,  in  ruminating  animals, 
127 

retarded  by  suppressing  saliva,  131 
Mecopium,  648 
Medulla  oblongata,  384,  439 

ganglia  of,  385,  386 

reiiex  action  of,  440 

effect  of  destroying,  442 

development  of,  638 
Meibomian  glands,  329 
Melanine,  103 

Membrane,  blastodermic,  688 
Membrana  granulosa,  567 
Membrana  tympani,  action  of,  508 
Memory,   connection   of,   with    cerebral 

hemispheres,  425 
Menobranchus,  size  of  blood-globules  in, 
220 

gills  of,  233 

spermatozoa  of,  557 
Menstruation,  570 

commencement  and  duration  of,  571 

phenomena  of,  571 

rupture  of  Graafian  follicles  in,  572 

suspended  during   pregnancy,  571, 
581 
Mesenteric  glands,  168,  317 
Michel,  Dr.  Myddleton,  rupture  of  Graaf- 
ian follicle  iu  menstruation,  572 
Milk,  333 

composition  and  properties  of,  333, 
334 

microscopic  characters,  335 


700 


INDEX. 


Milk,  souring  and  coagulation  of,  336 

variations  in,  during  lactation,  337 
Milk-sugar,  83 

converted  into  lactic  acid,  336 
Mollusca,  nervous  system  of,  375 
MooEE    AKD    Pennock,  experiments    on 

movements  of  heart,  275 
Motion,  400 

Motor  cranial  nerves,  449 
Motor  nervous  fibres,  403 
Motor  oculi  communis,  450 

externus,  451 
Movements,  of  stomach,  145 

of  intestine,  164 

of  heart,  273 

of  chest,  in  respiration,  237 

of  glottis,  240 

associated,  408 

of  foetus,  631 
Mucosine,  101 
Mucous  follicles,  327 
Mucous  membrane,  of  stomach,  133 

of  intestine,  151 

of  tongue,  483 

of  uterus,  554,  615 
Mucus,  327 

composition  and  properties  of,  328 

of  mouth,  125 

of  cervix  uteri,  554 
Muscles,  irritability  of,  388 

directly  paralyzed  by  suli^ho-cyanide 
of  potassium,  390 

consentaneous  action  of,  430 

of  respiration,  236 
Muscular  fibres,  of  spleen,  208,  209 

of  heart,  spiral  and  circular,  277 
Muscular  irritability,  388 

duration  after  death,  388 

exhausted    by  repeated    irritation, 
390 
Musculine,  102 

Nails,  formation  of,  in  embryo,  643 
Negkiee,  on  rupture  of  Graafian  follicle, 

in  menstruation,  572 
Nerve-cells,  372 
Nerves,  division  of,  372 

inosculation  of,  373 

irritability  of,  390 

spinal,  393 

cranial,  446 

olfactory,  446 

optic,  447 

auditory,  447 

oculo-motorius,  450 

patheticus,  451 

motor  externus,  451 

masticator,  452 
'  facial,  456 

hypoglossal,  477 

spinal  accessory,  474 

trifacial  (5th  pair),  451 

glosso-pharyngeal,  459 


Nerves,  pneumogastric,  461 

superior  and  inferior  laryngeal,  462 

great  sympathetic,  514 
Nervous  filaments,  368 

of  brain,  369 

of  sciatic  nerve,  370 

motor  and  sensitive,  375 
Nervous  force,  how  excited,  391 

nature  of,  395 
Nervous  tissue,  two  kinds  of,  368 
Nervous  irritability,  390 

how  shown,  391 

duration  of,  after  death,  391 

exhausted  by  excitement,  392 

destroyed  by  woorara,  393 

distinct  from  muscular,  395 

nature  of,  395 
Nervous  system,  365 

general  structure  and  functions  of, 
365-387 

of  radiata,  373 

of  mollusca,  375 

of  articulata,  376 

of  vertebrata,  379 

reflex  action  of,  374 
Network,  capillary,  in    Peyer's    glands, 
162 

in  web  of  frog's  foot,  296 

in  lobule  of  liver,  339 
Newly-born  infant,  weight  of,  687 

respiration  in,  687 

nervous  phenomena  of,  688 

comparative  size  of  organs  in,  689 
Newport,  on  temperature  of  insects,  256 
Nitric  acid,  action  of,  on  bile-pigment, 
184 

precipitation  of  uric  acid  by,  354 
Nitrogen,  exhalation  of,  in   respiration, 

242 
Nutrition,  61-364 

Obliteration,  of  ductus  venosus,  677 

of  ductus  arteriosus,  680 
Oculo-motorius  nerve,  450 
(Esophagus,  paralysis  of,  after  division 
of  pneumogastric,  463 

development  of,  645,  650 
ffistruation,  phenomena  of,  569 
Oleaginous  substances,  86 

in  di3"erent  kinds  of  food,  88 

condition  of,   in    the    tissues    and 
fluids,  88-93 

partly  produced  in  the  body,  93 

decomposed  in  the  body,  94 
in  the  blood,  170 

indispensable  as  ingredients  of  the 
food,  107 

insufiicient  for  nutrition,  108 
Olfactory  apparatus,  489 

protected  by  two  sets  of  muscles,  520 

commissures,  382,  418 
Olfactory  ganglia,  382,  418 

their  function,  418 


INDEX. 


70L 


Olfactory  nerves,  489 
Olivary  bodies,  384 
Omi^halo-meseuteric  vessels,  6G6 
Ophthalmic  ganglion,  514 
Optic  ganglia,  382,  434 
Optic  nerves,  447 

decussation  of,  436,437 
Optic  thalami,  418 

development  of,  638 
Organs  of  special  sense,  483,  489,  493, 
507 

development  of,  640 
Organic  substances,  95 

indefinite  chemical  composition  of, 
95 

hygroscopic  properties,  97 

coagulation  of,  98 

catalytic  action,  98 

putrefaction,  99 

source  and  destination,  104 

digestion  of,  141 
Origin,  of  plants  and  animals,  527 

of  infusoria,  529 

of  animal  and  vegetable  parasites, 
532 

of  encysted  entozoa,  534 
Ossification  of  skeleton,  642 
Osteiue,  102 
Otic  ganglion,  515 
Ovary,  541 

of  tjenia,  541 

of  frog,  547 

of  fowl,  551 

of  human  female,  553 
Ovaries,  descent  of,  in  foetus,  661 

condition  at  birth,  663 
Oviparous  and  viviparous  animals,  dis- 
tinction between,  563 
Oxalic  acid,  produced  in  urine,  360 
Oxygen,  absorbed  in  respiration,  242 

daily  quantity  consumed,  242 

state  of  solution  in  blood,  245 

dissolved  by  blood-globules,  245 

absorbed  by  the  tissues,  248 

exhaled  by  plants,  260 

Palate,  formation  of,  653 
Pancreatic  juice,  153 

mode  of  obtaining,  154 

composition  of,  155 

action  on  fat,  155 

daily  quantity  of,  155 
Pancreatine,  101 

in  pancreatic  juice,  155 
Pa>"I2za,  experiment  on  absoi-ption  by 

bloodvessels,  105 
Paralysis,  after  division  of  anterior  root 
of  sjjinal  nerve,  402 

direct,  after  lateral  injury  of  spinal 
cord,  405 

crossed,  after  lateral  injury  of  brain, 
405 

facial,  458 


Paralysis  of  muscles,  by  sulpho-cyanide 
of  potassium,  390 
of  motor  nei'ves,   by  woorara,  393, 

413 
of  sensitive  nerves,  by  strychnine, 

413 
of  voluntary  motion  and  sensation, 
after  destroying  tuber  annulare, 
438 
of   pharynx  and   oesophagus,  after 

section  of  pneumogastrics,  463 
of  larynx,  465,  467 
of  muscular  coat  of  stomach,  473 
Paraplegia,  reflex  action  of  spinal  cord 

in  411 
Parasites,  532 

conditions  of  development  of,  533 
mode  of  introduction  into  body,  534 
sexless,  reproduction  of,  535 
Parotid  saliva,  126 
Parturition,  633 

Par  vagum,  461.     See  Pneumogastric 
Patheticus  nerve,  451 
Pelouze,  composition  of  glycogenic  mat- 
ter, 204 
Pelvis,  development  of,  642 
Pennock  axd    Mooke,   experiments    on 

movements  of  heart,  275 
Pepsine,  101 

in  gastric  juice,  139 
Perception  of  sensations,  after  removal 
of  hemispheres,  422 
destroyed,  after  removal  of  tuber 
annulare,  438 
Periodical  ovulation,  563 
Peristaltic  motion,  of  stomach,  145 
of  intestine,  164 
of  oviduct,  548,  550 
Perkins,  Maurice,  composition  of  parotid 

saliva,  126 
Perspiration,  330 

daily  quantity  of,  331 
composition  and  properties  of,  331 
function,  in  regulating  temperatiire, 
331 
Pettenkofer's  test  for  bile,  185 
Peyer's  glands,  162 

Pharynx,  action  of,  in  swallowing,  460, 
461 
formation  of,  650 
Phosphate  of  lime,  its  proportion  in  the 
animal  tissues  and  fluids,  74 
in  the  urine,  353 
precipitated  by  alkalies,  354 
Phosphate,  triple,  in  putrefying  urine, 

362 
Phosphates,  alkaline,  77 
in  urine,  353 
earthy,  74,  77 

in  urine,  353 
of  magnesia,  soda,  and  potassa,  77 
Phosphorus,  not  a  proximate  principle,  63 
Physiology,  definition  of,  49 


702 


INDEX. 


Phrenology,  427 

objections  to,  428 

practical  difficulties  of,  428,  429 
Pigeon,  after  removal  of  cerebrum,  421 

of  cerebellum,  431 
Placenta,  621 

comparative  anatomy  of,  622 

formation  of,  in  human  species,  623 

fojtal  tufts  of,  625 

maternal  sinuses  of,  626 

injection  of,  from   uterine  vessels, 
627 

function  of,  628 

separation  of,  in  delivery,  633 
Placental  circulation,  624,  628 
Plants,  vital  heat  of,  256 

generative  apparatus  of,  540 
Plasma  of  the  blood,  223 
Pneumic  acid,  247 
Pneumogastric  nerve,  461 

its  distribution,  462 

action  of,  on  pharynx  and  oesopha- 
gus, 463 
on  larynx,  464 
in  formation  of  voice,  464 
in  respiration,  466 

effect  of  its  division  on  respiratory 
naovements,  466,  467 

cause  of  death  after  division  of,  470 

influence  of,  on  oesophagus  and  sto- 
mach, 473 
Pneumogastric  ganglion,  461 
PoGGiALE,  on  glycogenic  matter  in  but- 
cher's meat,  205 
Pons  Varolii,  387 
Portal  blood,  quantity  of  fibrin  in,  224 

tempei'ature  of,  262 
Portal  vein,  in  liver,  338 

development  of,  675 
Posterior  columns  of  spinal  cord,  381 
Primitive  trace,  590 
Production,  of  sugar  in  liver,  200 

of  carbonic  acid,  246 

of  animal  heat,  253 

of  urea  in  blood,  343 

of  infusorial  animalcules,  529 

of  animal  and  vegetable  parasites, 
532 
Proximate  principles,  61 

definition  of,  63 

mode  of  extraction,  64 

manner  of  their  association,  65 

varying  proportions  of,  6<> 

three  distinct  classes  of,  67 
Proximate  principles  of  the  first  class 
(inorganic),  69 

of  the  second  class  (crystallizable 
substances  of  organic  origin),  79 

of   the   third   class    (organic    sub- 
stances), 95 
Ptyaline,  124 
Puberty,  period  of,  565 

signs  of,  in  female,  570 


Pulsation,  of  heart,  270 

in  living  animal,  274 

of  arteries,  282 
Pupil,  action  of,  367,  435 

contraction  of,  after  division  of  sym- 
pathetic, 522 
Pupillary  membrane,  640 
Putrefaction,  99 

of  the  urine,  358 
Pyramids,  anterior,  of   medulla   oblon- 
gata, 384 

Quantity,  daily,  of  water  exhaled,  71 

of  food,  113 

of  saliva,  128 

of  gastric  juice,  147 

of  pancreatic  jiiice,  155 

of  bile,  188 

of  air  used  in  respiration,  238 

of  oxygen  used  in  respiration,  242 

of  carbonic  acid  exhaled,  250 

of  lymph  and  chyle,  320 

of  fluids  secreted  and  reabsorbed,  323 

of  material  absorbed  and  discharged, 
363 

of  perspiration,  331 

of  urine,  349 

of  urea,  344 

of  urate  of  soda,  348 
Quantity,  entire,  of  blood  in  body,  231 

Rabbit,  brain  of,  383 

Races  of  men,  different  capacity  of,  for 

civilization,  424 
Radiata,  nervous  system  of,  373 
Rapidity  of  circulation,  302 
Reactions,  of  starch,  82 

of  sugar,  84 

of  fat,  86 

of  saliva,  124,  125  .     - 

of  gastric  juice,  139 

of  intestinal  juice,  153 

of  pancreatic  jiiice,  155 

of  bile,  175 

of  mucus,  328 

of  milk,  334 

of  urine,  353 
Reasoning  powers,  425 

in  animals,  444 
Red  globules  of  blood,  213 
Reflex  action,  374 

in  centipede,  377 

of  spinal  cord,  408 

of  medulla  oblongata,  440 

of  tuber  annulare,  443 

of  brain,  444 

of  optic  tubercles,  435 

in  newly  born  infant,  688 
Regeneration,  of  uterine  mucous  mem- 
brane after  pregnancy,  633,  634 

of  walls  of  uterus,  635 
Regnault  and  Reiset,  on  absorption  of 
oxygen,  243 


INDEX. 


703 


Reid,  Dr.  John,  experiment  on  crossing 

of  streams  in  fo3tal  heart,  682 
Repi'oduction,  525 

nature  and  object  of,  525,  527 

of  parasites,  533 

of  taenia,  538 

by  germs,  540 
Reptiles,  circulation  of,  266 
Respiration,  232 

by  gills,  233 

by  lungs,  234 

by  skin,  252 

changes  in  air  during,  241 

changes  in  blood,  243 

of  newly  born  infant,  687 
Respiratory  movements  of  chest,  236 

of  glottis,  240 

after  section  of  pneumogastrics,  466 

after  injury  of  spinal  cord,  441 
Restiform  bodies,  385 
Rhythm  of  heart's  movements,  279 
Rotation  of  heart  during  contraction,  278 
Round  ligament  of  the  uterus,  formation 
of,  662 

of  liver,  677 
Rumination,  movements  of,  118,  127 
Rupture  of  Graafian  follicle,  568 

in  menstruation,  572 
Rutting  condition,  in  lower  animals,  569 

Saccharine  substances,  83 

in  stomach  and  intestine,  150 

iu  liver,  200 

in  blood,  207 

in  urine,  357 
Saliva,  123 

different  kinds  of,  125 

daily  quantity  of,  127 

action  on  boiled  starch,  129 

variable,  130 

does  not  take  place  in  stomach,  130 

physical  function  of  saliva,  131 

quantity  absorbed  by  different  kinds 
of  food,  132 
Salivary  glands,  125 
Salts,  biliary,  177 

of  the  blood,  225 

of  urine,  353 
Saponification,  of  fats,  87 
ScHAELiNG,  on  diurnal  variations  in  exha- 
lation of  carbonic  acid,  252 
ScucLTZE,  experiment  on   generation  of 

infusoria,  531 
Scolopendra,  nervous  system  of,  376 
Sebaceous  matter,  328 

compositioir  and  properties  of,  329 

function  of,  329 

in  fcctus,  643 
Secretion,  324 

varying  activity  of,  326 

of  saliva,  125 

of  gastric  juice,  137 

of  intestinal  juice,  152 


Secretion  of  pancreatic  juice,  154 

of  bile,  188,  337 

of  sugar  iu  liver,  200 

of  mucus,  327 

of  sebaceous  matter,  328 

of  perspiration,  330 

of  the  tears,  332 

of  bile  in  foetus,  649 
Segmentation  of  the  vitellus,  587 
Seminal  fluid,  556 

mixed  constitution  of,  560 
Sensation,  398 

remains  after  destruction  of  hemi- 
spheres, 422 

lost  after  removal  of  tuber  annulare, 
438 

special  conveyed  by  pneumogastric 
nerve,  440,  466,  468 
Sensation  and  motion,  distinct  seat  of,  in 
nervous  system,  400 

in  spinal  cord,  403 
Sensibility,  of  nerves  to  electric  current, 
391 

and  excitability,  definition,  of,  400 

seat  of,  iu  spinal  cord,  403 

in  brain,  417 

of  facial  nerve,  459 

of  hypoglossal  nerve,  477 

of  spinal  accessory,  475 

of  great  sympathetic,  517 
Sensibility,  general  and  special,  478 

special,  of  olfactory  nerves,  446, 489 

of  optic  nerves,  447 

of  auditory  nerves,  447 

of  lingual  branch  of  5th  pair,  484 

of  glosso-pharyngeal,  460 

of  pneumogastric,  468 
Sensitive  nervous  filaments,  375 
Sensitive  fibres,  crossing  of,  in  spinal  cord, 
405 

of  facial  nerve,  source  of,  459 
Sensitive  cranial  nerves,  449 
Septa,  inter-auricular  and  inter-ventri- 
cular, formation  of,  678,  680 
Skquard,  on  crossing  of  sensitive  fibres 

in  spinal  cord,  405 
Serum,  of  the  blood,  227 
Sexes,  distinctive  characters  of,  540 
Sexless  entozoa,  534 
Sexual  generation,  540 
Shock,  effect  of,  in  destroying  nervous 

irritability,  393 
SiEBOLD,   on   production    of  taenia   from 

cysticercus,  538 
Sight,  492 

apparatus  of,  493.     /See  Vision. 
Sinus  terminalis,  of  area  vasculosa,  665 
Sinuses,  placental,  624,  626 
Skeleton,  development  of,  641 
Skin,  respiration  by,  252 

sebaceous  glands  of,  328 

perspiratory  ghmds  of,  330 

development  of,  643 


704 


INDEX. 


Smell,  488 

ganglia  of,  382,  489 

nerves  of,  446,  489 

injured  by  division  of  5tli  pair,  454 
Smith,  Dr,  Southwood,  on  cutaneous  and 

pulmonary  exhalation,  331 
Solar  plexus  of  sympathetic  nerve,  516 
Solid  bodies,  vision  of  with  two  eyes,  502 
Sounds,  of  heart,  270 

how  produced,  271 

vocal,  how  produced,  464 

destroyed  by  section  of  inferior  la- 
ryngeal nerves,  465 
of  spinal  accessory,  475 
Sounds,  acute  and  grave,  transmitted  by 

membrana  tympani,  508 
Special  senses,  478 
Species,  mode  of  continuation,  527 
Spermatic  iiuid,  556 

mixed  constitution  of,  560 
Spermatozoa,  556 

movements  of,  558 

formation  of,  559 
Spina  bifida,  641 
Spinal  accessory,  474 

sensibility  of,  475 

communication  of,  with  pneumogas- 
tric,  475 

influence  of,  on  larynx,  475 
Spinal  column,  formation  of,  591,  641 
Spinal  cord,  379,  398 

commissures  of,  381 

anterior  and  posterior  columns,  381 

origin  of  nerves  from,  380 

sensibility  and  excitability  of,  403 

crossed  action  of,  404 

reflex  action  of,  408 

protective  action  of,  413,  414 

influence  on  sphincters,  414 

eff'ect  of  injury  to,  414 

on  respiration,  441 

formation  of,  in  embryo,  591,  645 
Spinal  nerves,  origin  of,  380 
Spleen,  208 

Malpighian  bodies  of,  209 

extirpation  of,  211 
Spontaneous  generation,  527 
Starch,  79 

proportion  of,  in  diflferent  kinds  of 
food,  80 

varieties  of,  80-82 

reactions  of,  82 

action  of  saliva  on,  129 

digestion  of,  150 
Starfish,  nervous  system  of,  373 
Stercorine,  160 
Stereoscope,  503 

St.  Martin,  case  of  gastric  fistula  in,  135 
Strabismus,  after  division  of  motor  oculi 
communis,  451 

of  motor  externus,  451 
Striated  bodies,  419 
Sublingual  gland,  secretion  of,  125 


Submaxillary  ganglion,  514 
gland,  secretion  of,  125 
Sudoriparous  glands,  330 
Sugar,  83 

varieties  of,  83 

composition  of,  84 

tests  for,  84 

fermentation  of,  85 

proportion  in  different  kinds  of  food, 

86 
source  and  destination,  86 
produced  in  liver,  200 
discharged  by  urine  in  disease,  357 
Sugar  in  liver,  formation  of,  200 
percentage  of,  202 
produced  in  hepatic  tissue,  203 
from  glycogenic  matter,  204 
absorbed  by  hepatic  blood,  206 
decomposed  in  circulation,  206 
Sulphates,  alkaline,  in  urine,  353 
Sulphur  of  the  bile,  181 

not  discharged  with  the  feces,  197 
Swallowing,  131 

retarded  by  suppression  of  saliva, 

133 
by  division  of  pneumogastric,  463 
Symj)athetic  nerve,  514 
its  distribution,  515 
sensibility  and  excitability  of,  517 
influence  of,  on  special  senses,  518 
on  pupil,  518 

on  nutrition  of  eyeball,  455 
on  nasal  passages,  520 
on  ear,  520,  521 

on   temperature   of    particular 
parts,  521 
reflex  actions  of,  524 

Tadpole,  development  of,  592 

transformation  into  fi'og,  594 
Tffinia,  536 

produced  by  metamorphosis  of  cys- 
ticercus,  538 

single  articulation  of,  541 
Tapeworm,  536 

mode  of  generation,  537 
Taste,  481 

nerves  of,  483 

conditions  of,  485 

injury  of,  by  paralysis  of  facial  nerve, 
487 
Taurine,  181 
Tauro-cholate  of  soda,  181 

microscopic  characters  of,  179 
Tauro-cholic  acid,  181 
Tears,  332 

their  function,  332 
Teeth,  of  serpent,  ]  21 

of  polar  bear,  122 

of  horse,  122 

of  man,  123 

first  and  second  sets  of,  689 
Temperature  of  the  blood,  254 


INDEX. 


705 


Temperature  of  different  species  of  ani- 
mals, 255 

of  the  blood  in  different  organs,  262 

elevation  of,  after  section  of  sympa- 
thetic nerve,  261,  521 
Tensor  tympani,  action  of,  506,  508 
Tests,  for  starch,  82 

for  sugar,  84 

for  bile,  184 

Pettenkofer's,  185 
Testicles,  559 

periodical  activity  of,  in  fish,  561 

development  of,  658 

descent  of,  658,  659 
Tetanus,  pathology  of,  410 
Thalami,  optic,  in  rabbit,  383 

in  man,  418. 

function  of,  419 
Thoracic  duct,  168,  170 
Thoracic  respiration,  441 
Tongue,  motor  nerve  of,  477 

sensitive,  452,  456,  483 
Trichina  spiralis,  535 
Tricuspid  valve,  268.    See  Auriculo-ven- 

tricular 
Triple  phosphate,  in  putrefying  urine,  362 
Trommer's  test  for  sugar,  84 

interfered  with  by  gastric  juice,  143 
Tuber  annulare,  386,438 

effect  of  destroying,  438 

action  of,  439 
Tubercula  quadrigemina,  382,  434 

reflex  action  of,  435 

crossed  action  of,  436 

development  of,  637,  638 
Tubules  of  uterine  mucous  membrane, 

615 
Tufts,  placental,  625 

Tunica  vaginalis  testis,  formation  of,  660 
Tympanum,  function  of,  in  hearing,  508 

Umbilical  cord,  formation  of,  631 

withering  and  separation  of,  689 
Umbilical  hernia,  646 
Umbilical  vesicle,  596 

in  human  embryo,  597 

in  chick,  604 

disappearance  of,  631 
Umbilical  vein,  formation  of,  6G9 

obliteration  of,  677 
Umbilicus,  abdominal,  592 

amniotic,  600 

decidual,  617 
Unilateral   mastication,   in   ruminating 

animals,  127 
Urate  of  soda,  347 

its  properties,  source,  daily  quantity, 
&c.,  34.^ 
Urates  of  potassa  and  ammonia,  348 
UrachuH,  647 
Urea,  343 

source  of,  343 

mofle  of  obtaining,  344 

45 


Urea,  conversion  into  carbonate  of  am- 
monia, 344 
daily  quantity  of,  344 
diurnal  variations  in,  345 
decomposed  in  putrefaction  of  urine, 
360 

Uric  acid,  347,  354 

Urine,  349 

general  character  and  properties  of, 

349 
quantity  and  specific  gravity,  350 
diurnal  variations  of,  351 
composition  of,  352 
reactions,  353 

interference  witli Trommer's  test,  355 
accidental  ingredients  of,  355 
acid  fermentation  of,  359 
alkaline  fermentation  of,  360 
final  decomposition  of,  363 

Urinary  bladder,  paralysis  and  inflam- 
mation of,  after  injury  to  spinal 
cord,  415 
formation  of,  in  embryo,  647 

Urosacine,  103 

Uterus,  of  lower  animals,  553 
of  human  female,  554 
mucous  membrane  of,  614 
changes  in,  after  impregnation,  615 
involution  of,  after  delivery,  634 
development  of,  in  foetus,  661 
position  of,  at  birth,  663 

Uterine  mucous  membrane,  614 
tubules  of,  615 
conversion  into  decidua,  615 
exfoliation  of,  at  the  time  of  delivery, 

633 
its  renovation,  634 

Valve,  Eustachian,  681 

of  foramen  ovale,  684 
Valves,  cardiac,  action  of,  268 

cause  of  heart's  sounds,  271 
Vasa  deferentia,  formation  of,  658 
Vapor,  watery,  exhalation  of,  71 

from  lungs,  242 

from  the  skin,  252 
Variation,  in  quantity  of  bile  in  different 
animals,  188 

in  production  of  liver-sugar,  202 

in  size  of  spleen,  208 

in  rapidity  of  coagulation  of  blood, 
227 

in  size  of  glottis  in  respiration,  240 

in  exhalation  of  carbonic  acid,  250 

in  temperature  of  blood  in  different 
parts,  262 

in  composition  of  milk  during  lac- 
tation, 337 

in  quantity  of  urea,  345 

in  density  and  acidity  of  urine,  350 
Varieties  of  starch,  80 

of  sucar,  83 

of  fat"  86 


706 


IXDEX. 


Varieties  of  biliary  salts  in  different  ani- 
mals, 182 
Vegetable  food,  necessary  to  man,  106 
Vegetable  parasites,  532 
Vegetables,  production  of  heat  in,  256 

absorption  of  carbonic  acid  and  ex- 
halation of  oxygen  by,  49,  2G0 
Vegetative  functions,  58 
Veins,  290 

their  resistance  to  pressure,  290 

absorption  by,  16-5 

action  of  valves  in,  293 

motion  of  blood  through,  291 

rapidity  of  circulation  in,  294 

omphalo-mesenteric,  666 

umbilical,  669 

vertebral,  672 
Vense  cava,  formation  of,  673 

position  of,  in  fcetus,  681 
Vena  azygos,  superior  and  inferior,  for- 
mation of,  673 
Venous  system,  development  of,  672 
Ventricles  of  heart,  single  in  fish  and 
reptiles,  265,  266 

double  in  birds  and  mammalians, 
267 

situation  of,  268 

contraction  and  relaxation  of,  269 

elongation  during  contraction,  275 

muscular  fibres  of,  277 
Vernix  caseosa,  643 
Vertebrata,  nervous  system  of,  378 
Vertebrae,  formation  of,  591,  641 
Vesicles,  adipose,  90 

pulmonary,  235 

seminal,  560 
Vesiculse  seminales,  560 

formation  of,  660 
Vicarious  secretion,  non-existence  of,  325 
Vicarious  menstruation,  nature  of,  325 
Villi,  of  intestine,  163 

absorption  by,  164 

of  chorion,  609-611 
Vision,  492 

ganglia  of,  382,  434 

nerves  of,  447,  493 

apparatus  of,  493 

distinct,  at  different  distances,  496 

circle  of,  499 


Vision,  of  solid  bodies  with  both  eyes,  502 
Vital  phenomena,  their  nature  and  pecu- 
liarities, 54 
Vitellus,  541 

segmentation  of,  587 

formation  of,  in  ovary  of  foetus,  663 
Vitelline  circulation,  665 

membrane,  544 

spheres,  587 
Vocal  sounds,  how  produced,  464 
Voice,  formation  of,  in  larynx,  464 

lost,  after  division  of  spinal  acces- 
sory nerve,  475 
Volition,  seat  of,  in  tuber  annulare,  438 
Vomiting,    peculiar,    after    division    of 
pneumogastrics,  473 

Water,  as  a  proximate  principle,  69 

its  proportion  in  the  animal  tissues 

and  fluids,  70 
its  source,  70 

mode  of  discharge  from  the  body,  71 
Weight  of  organs,  in  comparative,  newly 

born  infant  and  adult,  689 
White  globules  of  the  blood,  220 
action  of  acetic  acid  on,  221 
sluggish  movement  of,  in  circula- 
tion, 297 
White  substance,  of  nervous  system,  368 
of  Schwann,  368 
of  spinal  cord,  380 
of  brain,  insensible  and  inexcitable, 
417 
Withering  and  separation  of   umbilical 

cord,  after  birth,  689 
Wolifian  bodies,  655 
structure  of,  656 
atrophy  and  disappearance  of,  656, 

657 
vestiges  of,  in  adult  female,  662 
Wtman,  Prof.  Jeffries,  on  cranial  nerves 
of  Rana  pipiens,  449 
fissure  of  hare-lip  on  median  line, 
637 

Yellow  color,  of  urine  in  jaundice,  357 
of  corpus  luteum,  579 

Zona  pellucida,  544 


THE    END, 


HEISrHY     C.    LEA.'S 

(late  lea  &  elanchard's) 
or 

MEDICAL  AND  SUEGICAL  PUB"LI0ATI01?S. 


In  asking  tlie  attention  of  the  profession  to  tlie  works  contained  in  the  following 
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An  Illustrated  Catalogue,  of  64  octavo  pages,  handsomely  printed,  will  be  for- 
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HENRY  C.  LEA. 

Nos.  706  aad  708  Sansom  St.,  Philadelphia,  September,  1866. 


THE  AMERICAN  JOURNAL  OF  THE  MEDICAL  SCIENCES. 


WITH    THE 


MEDICAL  NEWS  AND  LIBRARY. 

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a  very  condensed  summary  of  the  contents  of  the  last  two  numbers  of  the  "Journal." 

SUMMAE.Y  OF  CONTENTS  OF  No.  101,  NEW  SERIES,  FOS  JANUAEY,  1866. 


MEMOIRS  AND  CASES. 

I.  Researclies  on  Typhus  Fever.  By  J.  M.  Da  Costa, 
M.  D  ,  of  Philadelphia.  '• 

II.  On  the  Cause  of  Intermittent  and  Remittent  Fe- 
vers" traced  to  certain  species  of  Palmellse.  By 
J   H.  Sali.sbury,  M.  D  ,  of  Cleveland,  Ohio. 

III.  On  the  Causes  of  Certain  Diseases  on  Ships  of 
War.     By  Edgar  Holden,  M.  D.,  of  Newark.  N.  J. 

IV  Comparative  advantages  of  Pimgoffs,  Syme's,  and 
Chopai't's  Amputations,  and  Excision  of  the  Ankle- 
Joint,  by  Hancock's  Method,  with  the  proposition 
of  anolber  Method  for  Excision.  By  James  M.  Hol- 
loway,  M.  D  ,  of  Louisville,  Ky. 

V.  On  Symptomatic  Bronchial  In-itation.  By  A.  P. 
Merrill,  M.  D.,  of  New  York  City. 

VI.  On  Puerperal  Tetanus.  By  Wm.  A.  Gordon,  M.D., 
New  Bedford,  Mass. 

VII  The  Use  of  the  Artificial  Membrana  Tympani. 
By  D.  B   St   John  Roo.sa,  M.D.,  of  New  York. 

VIII.  Successful  Removal  of  the  Uterus  and  both 
Ovaries  by  Abdominal  Section.  By  Horatio  K. 
Storer,  M,  D.,  of  Boston. 

IX.  Cases  of  Excision  of  Bones.  By  James  B  Cutter, 
M.  D.,  of  Newark,  N.  J.    (With  two  wood-cuts.) 

X.  Amputation  of  Right  Shonlder-Joiut.  By  W.  P. 
Moou,  M.  D  ,  Chestnut  Hill.  Pa     (Vi^.th  a  wood-cut  ) 

Xr.  A  Peculiar  Case  of  Hajiuatocele.  By  Charles  M. 
AUiu,  M.  D.,  o(  New  York. 

XII.  Instruments  for  Facilitating  Surgicnl  Opera- 
tions. By  D.  Prince,  M.  D.,  of  Jacksonville,  111. 
{With  two  wood-cuts  ) 

XIII.  Reduction  of  an  Inverted  Uterus  of^  Seven 
Months'  Standing.  By  Tliomas  Addis  Emmel,  M.D., 
of  New  York. 

TRANSACTIONS  OF  SOCIETIES. 
X  !V.  Siiiinnary  of  tlie  Transactions  of  the  College  of 
Fhysiciaas  of  Philadelphia. 
ManiTiiary  Cancer.    By  John  A'ihhurst,  Jr.,  M.D. 
— Report  on  Meteorology  and  Epidemics  for  the 
year  ending  January  1st,  1860.     By  James  M. 
Cor.se,  M  D — Cancer  of  the  Ascending  Colon. 
By  Alfred  Still(5,  M.  D— Regeneration  of  Bone. 
By  William  Hunt,  M.D — Tumor  on  the  Poste- 
rior Portion  of  the  Tongue.   By  Wm  Hunt,  MD. 
— Fatal  Perltouilis  in  Typhoid  Fever,  without 
Perforation  of  the  Bowel.  By  Alfred  Slill6,  M.D. 

REVIEWS. 

XV,  Cliuiqne  M^dicale  de  rilotel-Dieu  de  Paris.  Par 
A.  Tronsseaa.  Deuxierae  Edition,  revue  et  aug- 
mrtui6e.  I 

XVI.  Lectures  on  the  Pathology  and  Treatment  of  ! 
Lateral  and  other  Forms  of  Curvature  of  the  Spine,  i 
By  William  Adaas,  F.  R.  C.  S.  | 


BIBLIOGRAPHICAL  NOTICES. 

XVII.  Transactions  of  the  Medical  Society  of  the 
State  of  Pennsylvania,  at  its  Sixteenth  Annual  Ses- 
sion, held  at  Altoona,  June,  186.5 

X  VIII.  Reports  of  American  Hospitals  for  the  Insane. 

XIX.  The  Practice  of  Medicine  and  Surgery  applied 
to  the  Diseases  and  Accidents  incident  to  Women. 
By  Wm.  H   Byford,  A.M  ,  M.D. 

XX.  Materia  Medica  for  the  Use  of  Students.  By 
John  B.  Biddle,  M.D. 

XXI.  On  the  Direct  lufluence  of  Medicinal  and  Mor- 
bific Agents  upon  the  Muscular  tissue  of  the  Blood- 
vessels.    By  R.  Cresson  Stiles,  M  D.,  etc. 

XXII.  Obscure  Diseases  of  the  Brain  and  Mind.  By 
Forbes  Winslow,  M  D.,  DC  L. 

XXIII.  An  Inquiry  into  the  Possibility  of  Restoring 
the  Life  of  Wann-Blooded  Animals  in  certain  cases. 
By  Benjamin  Ward  Richardson,  M  A..  M.D 

XXIV.  The  Practice  of  Medicine.  By  Thomas  Hawkes 
Tanner,  M  D.,  F  L  S. 

XXV.  The  Principles  of  Surgery.  By  James  Syme, 
F.  R.  S.  E. 

XXVI.  The  Essentials  of  Mat<>ria  Bledica  and  Thera- 
peutics.   By  Alfred  Baring  Garrod,  M.D  ,  F.R.S. 

XXVII.  Lectures  on  the  Diseases  of  the  Stomach. 
By  William  Brinton,  M  D..  F  R  S. 

XXVIII.  A  Rei'ort  upon  the  Epidemic  occurring  iit 
Maplewooil  Young  Ladies'  Institute,  Pittslield, 
Mass.,  in  July  and  August,  1S64. 

XXIX.  Leclures  on  Epilepsy,  Pain,  Paralysis,  &c. 
By  Charles  Bland  Radcliffe,  M  D. 

XXX.  Patologia  e  Terapia  delle  Malattie  Veneiee  di 
F.  J  Burnsioad  — Buinstead's  Patliolngy  aud  Treat- 
ment of  Venereal  Diseases.  Translated  into  the 
Italian  by  Dr.  Cirillo  Tamburiiii. 

QUARTERLY  SUMMARY. 

FOREIGN     INTELLIGENCE. 

Anatomy  and  PHTsiOLoaT. 

1.  On  Life.     By  Dr   Beale. 

2.  Experiments  to  determine  the  Activity  of  the 
Spleen.     By  MM   Estor  and  St.  Pierre. 

3.  Deglutition  as  observed  by  Autolaryngo.scopy.  By 
M   Guinier. 

4.  Influence  of  Galvanism  on  the  Heart    By  Dr  Flies. 

5.  Experiments  on  Congelation  of  Animals.  By  M. 
Pouchet. 

6.  Cell-Pathology.     By  Dr.  Bennett. 

Materia  Medica  and  Pharmacy. 

7.  Danger  of  Subcutaneous  Injections.  By  Prof. 
Nassbaum. 

8.  Action  of  Certain  of  the  Anayl  Compounds.  By 
Dr   B.  W.  Richardson. 


Henry  C.  Lea's  Publications — (Am.  Journ.  Med.  Sciences). 


9.  Modification  in  Canquoin's  Caustic  Paste. 

10.  New  Ansesthetic  Mixture.    By  M.  Brown,  Jr. 

Medical  Patholohy  and  Thbrapedtics, 
AND  Practical  Medicine. 

11.  The  Use  of  the  Thermometer  in  Acute  Disease. 
By  Dr.  Ringer. 

12.  Hydatids  of  the  Liver,  their  Diagnosis,  and  their 
Treatment.     By.  Dr.  Murchison. 

13.  Children's  Diseases.     By  M.  Roger. 

14.  Aphtha;  of  the  Mouth  and  Throat.    By  Dr.  Wilks. 
1.5,  Malignant  Pustule.     By  M.  Davaine. 

16.  Animal  Parasite  Diseases  of  the  Skin.     By  Dr. 
Squire. 

17.  Degeneracy  of   Vaccine    Lymph    by   Frequent 
Transmission.     By  Mr.  Harding 

18.  Assimilation  of  Fat  in   Consumption.     By  Dr. 
DobeU. 

19.  Inhalation  of  Oxygen  in  Phthisis  and  Ansemia. 
By  Dr.  Wolff. 

20.  Use  of  Phenic  Acid  for  the  Cure  of  Phthisis.     By 
Dr.  Wolff. 

21.  Instantaneous  Cure  of  Coryza.     By  M.  Luc. 

22.  Bronzing  of  the  skin  for  Seven  Years — Disease  of 
Supra-renal  Capsules. 

23.  Climactei'ic  Insanity  in  the  Male.     By  Dr.  Skae. 

Surgical  Pathology  and  Therapeutics, 
AND  Operative  Surgery. 

24.  Osteo-myelitis.     By  Dr.  Fayrer. 

25.  Treatment  of  Hereditary  S'yphilis  without  Mer- 
cury.    By  Mr.  Dunn. 

26.  Traumatic  Tetanus  successfully  treated  by  Opium 
Smoking,  Chloroform,  and  Hemp.    By  Dr.  Fayrer. 

27.  Subcutaneous  Section  of  Carbuncle.  By  Mr.  Heath. 

28.  Enlarged  Spleen  Removed  by  Excision,     By  Mr. 
Wells. 

29.  Entire  Tongue  Saccessfully  Removed.     By  Mr. 
Nunneley. 

30.  Congenital   Luxation   of   the  Patella.      By*'  Mr. 
William  Stokes. 

31.  Compound  Dislocation  of  the  Astragalus — Reduc- 
tion.    By  Dr.  Grant. 

32.  Fissured  Fracture  of  the  External  Table  of  the 
Skull.     By  Mr.  Teevan. 

33.  Fi'acture  of  the   Larynx;   Tracheotomy;    Reco- 
very.   By  Dr.  Macleau. 


Ophthalmology. 
34.  Strumous  Ophthalmia.     By  Mr.  Johnson. 
3.i.  Blennorrhagic  Conjunctivitis  treated  by  Alcohol. 
By  M.  Gossplin. 

36.  Sympathetic  Ophthalmia.  By  MM.  Guepin  and 
Wecker. 

37.  Retinal  Disease  occurring  in  the  Course  of  Kidney 
Disease.  By  Mr.  Hnlke,  Mr.  Hart,  and  Mr.  Hutch- 
inson. 

38.  Graves'  Disease.     By  Dr.  Reith. 

39.  Black  Cataract.     By  Mr.  Nunneley. 

Midwifery. 

40.  Mortality  of  the  Childbed  as  Afifected  by  the  Num- 
ber of  tlie  Labor.     By  Dr.  Duncau. 

41.  Fatal  Case  of  Accidental  Hemorrhage.  By  Dr. 
Young. 

42.  Rnpture  of  the  Uterus  ;  Abdominal  Section  ;  Sub- 
sequent Pregnancies.     By  Dr.  Dyer. 

43.  Extra-Uterine  Flotation.     By  Dr.  Hicks. 

44.  Intra-Uterine  Variola.     By  M.  Legros. 

45.  Retention  of  Urine  in  the  Fcetus.     By  M.  Depuul. 

Hygiene. 

46.  Ozone.     By  Dr.  Richardson. 

47.  On  the  Effects  of  Scanty  and  Deficient  Food.  By 
Dr.  Davy. 

48.  Does  a  Diet  of  Animal  Food  Conduce  to  Lean- 
ness ?     By  Dr.  Davy. 

49.  Beef  and  Pork  as  Sources  of  Entozoa.  By  Dr. 
Cobbold. 


AMERICAN   INTELLIGENCE. 

Original  CoMMU:;ic.vrioNs. 

Exsection  of  two  and  one-half  inches  of  the  Right 

Tibia.     By  W,  Kerapster,  M  D. 
Paralysis  of  the  Median   Nerve.     By  J.   W.  Moor- 
man, M.D. 
Sycosis  cured  by  Sulphite  of  Soda.  By  J.  Y.  Dale,  M.D. 

Domestic  Summary. 
Dermoid  Tumour  of  the  Conjunctiva.  By  Dr.  Sprague. 
Action  of  the  Bromide  of  Potassium.  By  Dr.  Bartholow. 
Treatment  of  Paralysis  in  Children.    By  Dr.  Wm.  A. 

Hammond. 
Uterine  Tumors.     By  Dr.  Sands. 
Bifid  Uterus  and  Double  Vagina.     By  Br.  Hoyt. 


SUMMARY  OF  CONTENTS  OF  No.  102,  H'SW  SSUIES,  FOE  APEIL,  1866. 


MEMOIRS  AND  CASES. 

I.  Microscopic  Researches  on  the  Histology  and  Mi- 
nute Anatomy  of  the  Spleen  and  Lacteal  and  Lym- 
phatic Glands.  By  J.  H.  Salisbury,  M.D.,  Cleve- 
land, Ohio.     (With  a  plate.) 

II.  Reflections  upon  the  Epidemic  of  Yellow  Fever  at 
Pensacola  in  1863.     By  B.  F   Gibbs,  M  D  ,  U.  S.  N. 

III.  Hospital  Gangrene  at  Patterson  Park  Hospital, 
Bait.     By  W.  Kempster,  M.D.,  of  Syracuse,  N  Y. 

IV.  On  Ether  as  a  Local  Application.  By  J.  J.  Black, 
M.D.,  of  Philadelphia. 

V.  On  Chloroform  and  Ergot  in  Obstetric  Pi'actice. 
By  Charles  C.  Hildreth,  M.D.,  of  Zanesville,  Ohio. 

VI.  On  some  of  the  Diseases  prevailing  among  the 
Freed)>enple  in  the  Di.st.  of  Col.  Bv  Robert  Rev- 
burn,  AI  D.,  Washington,  D.C. 

VU.  Ou  Torpedo  Wounds.  By  S.  W.  Gross,  M.D.,  of 
Philadelphia. 

Vni.  Case  of  Neuralgic  and  Paralytic  Affection  fol- 
lowing Labor.  By  Isaac  G.  Porter,  M.  D.,  New 
Lond'in,  Conn. 

IX.  On  Fractures  of  the  Larynx  and  Ruptures  of  the 
Trachea.     By  Wm    ilant,  M.D.,  of  Philadelphia. 

X.  Report  of  Eight  Cases  of  Lithotomy.  By  Paul  F. 
Eve,  M  D  ,  of  Nashville.Tenn. 

XI.  On  Hypersulpliite  of  Soda  in  Intermittent  Fever. 
By  T.  U.  Leavilt,  M  D.,  of  Gerraantown,  Pa. 

XII.  On  the  Treatment  of  Certain  Chronic  and  Acute 
Aaection.s  of  the  .Skin  by  Clilori.le  of  Iron.  By 
Bedford  Brown,  M  D.,  of  Washington  City,  0.  C. 

XIII.  Shoulder  Presentation  in  Fonr  Successive  La- 
bors. ByChiirlesC.  Hildreth,  M.D., of  Zanesville,  O. 

XIV.  Case  of  Ovariotomy.  By  James  E.  Reeves, 
M.D.,  Kainuont,  W.  Va. 

XV.  Keduc'.ion  of  an  Inverted  T'terus  of  Eight 
Months'  Duration.  By  Thoraaii  AddinEmmett,  M.D  , 
New  ifork. 

TI{AN8ACTI0NS  OF  SOCIETIES. 

XVI.  Sninniary  of  the  Proceedin^tt  of  tl-e  I'atbological 


Sociuiy  uf  Philadelphia. 


Remittent  Fever ;  Pigment  in  all  Tissues  of  Body. 
By  Wm.  Pepper,  M.  D.— .Icute  Infiltrated  Tu- 
bercle Associated  with  Malaria.  By  Wm.  Pep- 
per, M.D. —  Remittent  Fever;  Pigment  in  the 
Brain,  &c.  By  Wm.  Pepper,  M.D. — Tubercular 
Meningitis.  By  T.  H.  Andrews,  M.D — Spina 
Bifida;  Fatty  Kidney.  By  Dr.  Packard.— 
Fracture  of  Base  of  Skull.  By  Dr.  Wm.  Pepper. 
— Fracture  of  Right  Temporal  Bone.  By  Dr. 
Wm.  Pepper. — Gunshot  Wound  through  Thy- 
roid Gland.  By  Win.  Pepper,  M.D. — Medullary 
Cancer.  By  S.  W.  Mitchell,  M.D. — Examination 
of  Tumour.  By  Wm.  Pepper,  M.D. — Lithotomy. 
By  John  Ashhurst,  Jr.,  M.D.— Polypi  of  the 
Vocal  Chords.  By  S.  W.  Mitchell,  M.D  —Sup- 
purative Meningitis  following  Coinminnted 
Fracture  of  the  Kasal  Bones.  By  Wm.  Pepper, 
M.  D.— Abscess  of  the  Spleen.  By  George  Pep- 
per, M.  D. 

REVIEWS. 

XVII.  Hypodermic  Injections  in   the  Treatment  of 
Disease. 

XVIII.  Stimulants   and   Narcotics.      By  Francis  E. 
Anstie,  M.D.,'M.R.P.C. 

XIX.  Laryngoscopy. 

BIBLIOGR.iPHICAL  NOTICES. 

XX.  Transactions  of  American  State  Medical  Societies. 

XXI.  Reports  of  American  Hospitals  for  the  Insane. 

XXII.  Guy's  Hospital  Reports. 

XXIIJ.   On  tlie  Arrangement  of  the  Muscular  Fibres 

in   the   Ventricles   of   the   Vertebrate   Heart.     By 

James  Bell  I'etiigrew.  M.D. 
On  the  Rulaliiin,  Stnictnre,  and  Function  of  the  Valves 

of  the  N'ascular  System  in  Vertobrata.     By  Jainos 

B«ll  Pettigrew,'M!D. 
XXI  V.  Essay  on  the  Use  of  the  Nitrate  of  Silver  in  the 

'I'n-atment  of  Inflammation,  Wounds,  and  Ulcers. 

By  John  Higginbottom,  F,  K.  S 
XXV.    Couirihutions   to   Done   and   Nerve  Surgjry. 

By  J.  C.  Nott,  M.D. 


Henry  C.  Lea's  Publications — (Am.  Journ.  Med.  Sciences). 


XXVI.  On  Wakefulness.  By  Wm.  A.  Hammond,  M.D. 

XXVII.  Annual  Report  of  the  Surgeon-General  U.  S.  A. 
1S6.5. 

XXVIII.  The  Student's  Book  of  Cutaneous  Medicine. 
By  Erasmus  Wilson,  P.  R.  S. 

XX'lX.  On  the  Diseases,  Injuries,  and  Malformations 
of  the  Rectum  and  Anus.     By  T.  J.  Ashton. 

XXX.  Lectures  on  the  Diseases  of  Infancy  and  Child- 
hood.   By  Charles  West,  M.D. 


QUARTERLY  SUMMARY. 

FOREIGN     INTELLIGENCE. 
Anatomy  and  PnrsioLOGr. 

1.  The  Functions  of  the  Nucleus.     By  M.  Balhiani. 

2.  Decomposition  of  Air  by  the  Tissues.  By  M.  De- 
marquay 

3.  Production  of  Animal  Heat.     By  M.  Berthelot. 

4.  Exi.-itence  of  Glycogen  in  the  Tissue  of  Entozoa. 
By  Mr.  Foster. 

Materia  Medica  and  Pharmacy. 

5.  New  and  Ready  Mode  of  Producing  Anjesthassia. 
By  Dr.  B.  W.  Richardson. 

6.  Au;esthetic  and  Sedative  Properties  of  Bi-Chloride 
of  Carbon.     By  Prof.  Simpson. 

7.  Solanum  Paniculatum      By  M.  Martin. 

S.  Physiological  Action  of  Iron.     By  Dr.  A.  Sasse. 

Medical  PATeoLOGY  and  Therapedtics, 
AND  Practical  Medicine. 
9.  The  Polymorphism  of  Disease. 
10    Medical  Statistics.     By  M.  Bernard. 

11.  Morbid  Anatomy  and  Early  Signs  of  Pneumonia. 
By  Dr.  Waters. 

12.  Certain  Forms  of  Haemoptysis..  By  Dr.  Cotton. 

13.  Snow's  Theory  of  the  Causes  of  Cholera.  By  Dr. 
Richardson. 

14.  Efficacy  of  Lemon-Juice  in  Diphtheria.  By  M. 
Guersant. 

15.  Hyposulphite  of  Soda  in  Diphtheria.  By  Mr.  J. 
C.  Maynard. 

16.  Treatment  of  Articular  Rheumatism,  &c.  by  the 
Subcutaneous  Injection  of  Sulphate  of  Quinia.  By 
Dcdenil. 

17     The   Hot   Mustard    Hip-bath    in  Diarrhoea   and 

Choleraic  Diarrhoea.     By  Dr.  Joseph  BuUar. 
IS.  Atropia  in  Constipation.     By  Dr.  Fleming. 

19.  Curability  of  Bvight's  Disease.     By  Dr.  Hassall. 

20.  Entozoa  in  the  Muscles  of  Animals  Destroyed  by 
Cattle  Plague.     By  Mr.  Beale. 

21-.  Outbreak  of  Trichinosis  at  Hedersleben.  By  Dr. 
Kratz. 

22.  Diagnosis  by  the  Ophthalmoscope.  ByM.  Bouchut. 

Surgical  Pathology  and  Therapeutics, 
AND  Operative  Surgery. 

23.  Use  of  Chloride  of  Zinc  for  Removal  of  Cancerous 
Tumors.     By  Mr.  De  Morgan. 

2t.  Subcutaneous  Ulceration.     By  Mr.  Paget. 

2j.  Cancer  of  the  Testis  in  Children.  By  M.  Guersant. 


26.  Arterio-Venous    Cyst    in   the  Popliteal    Nerve. 
By  Mr.  Moore. 

27.  Removal  of  the  entire  Tongue  by  the  Ecraseur. 
By  Mr.  Paget. 

28.  Excision  of  the  Tongue.     By  Prof  Jas.  Syme. 

29.  Foreign  Bodies  iu  the  Air-Passages  of  Children. 
By  M.  Guersant. 

.30.  Polypi  of  Larynx.     By  Dr.  Gilew.ski. 

31.  Wounds  of  Joints.     By  Dr.  Rutherford. 

32.  The  Sequel  in  Excision  of  Joints. 

33.  Trephining  the  Spine.     By  Dr.  Gordon. 

34.  Ovariotomy  in  Relation  to  Disease  of  both  Ova- 
ries.    By  M.  Scanzoni. 

Ophthalmology. 

35.  Changes  in  the  Eye  in  Progressive  Myopia.    By 
Mr.  Rouse. 

36.  Physiology  and  Pathology  of  Dilated  Pupil.    By 
Dr.  Bell. 

37.  Atropia  Points.     By  Mr.  Laurence. 

Midwifery. 

38.  Use  of  the  Wire-Ribbon  in  Difficult  Turning.    By 
Dr.  Heyerdahl. 

39.  Intluence  of  Chloi-ate  of  Potash  on  the  Foetus  ia 
Utero.     By  Dr.  Bruce. 

40.  Procidentia  Uteri.     By  Dr.  Sims. 

Hygiene. 

41.  Ozone  for  Sanitary  Purposes.     By  Dr.  Day. 

42.  Deodorization  and  Disinfection.     By  Dr.  Baker. 

43.  Utilization  of  Fecal  Matter.     By  Dr.  Lecadre. 

Medical  Jurisprudence  and  Toxicology. 

44.  Death  from  Chloroform.     By  Dr.  Gillespie. 

45.  Respiration  and  Signs  of  Life  in  a  Five  Months' 
Fcetus.     By  Dr.  Moore. 


AMERICAN   INTELLIGENCE. 
Original  Communication.^. 
Case  of  Prolapsus  Recti.     By  John  Peach,  M.D, 
Case  of  Tapeworm  Probably  Contracted  by  Eating 

Beef  or  Veal.     By  J.  H.  Beech,  M.D. 
Poisoning  by  the  Fruit  of  Rhus  Toxicodendron.     By 

J.  W.  Moorman. 
Spontaneous  Umbilical  Hemorrhage.  By  J.  H.  Pooley, 

M.  D. 

Domestic  Summary. 
Aphasia.     By  Prof.  Austin  Flint. 
Gutta-Pei'cha  Shoe  in  Talipes.     By  Dr.  Post. 
Amputation  at  Hip-Joint.     By  Dr.  Fauntleroy. 
Colotomy  for  Cancer  of  the  Rectum.    By  Prof.  Black- 

mau. 
Gunshot  Wound  of  the  Brain.     By  Dr.  Hutchinson. 
Dislocation  of  the  Patella  on  its  Axis.     By  Dr.  Ro- 
chester. 
Dislocation  of  the  Thigh  upon  the  Dorsum  Ilii.     By 

Dr.  Fauntleroy. 
Constituents  of  Veratrum  Viride.     By  Mr.  Charles 

Bullock. 
The  late  Professor  Chandler  R.  Gilman. 


By  reference  to  the  terms,  it  will  be  seen  that,  in  addition  to  this  large  amount  of  valuable 
practical  matter,  the  subscriber  receives,  without  further  charge, 

THE    MEDICAL    NEWS    AND    LIBRARY, 

a  monthly  periodical  of  thirty-two  large  octavo  pages.  Its  News  Department  presents  the  cur- 
rent information  of  the  day,  and  for  some  months  pa.<;t  there  has  been  a  section  devoted  especially 
to  the  sul)ject  of  Cholera.  Its  Library  Depai-tment  is  occupied  with  standard  works  on  practical 
medicine,  and  in  its  pages  have  been  presented  to  the  profession  many  of  the  most  important  trea- 
tises of  the  age,  such  as  Watson's  Practice,  Malgaigne's  Surgery,  Todd  &  Bowman's  Phy- 
siology, West  on  Children,  Simpson  on  Females,  &c.  &e.  The  work  now  appearing  in  its 
columns  is  Jones  on  Functional  Nertous  Disorders,  of  which  a  description  will  be  found  on 
p.  20,  and  which  will  be  continued  to  completion  in  1866. 

It  will  thus  be  seen  that,  notwithstanding  the  very  great  increase  in  the  cost  of  production,  sub- 
scribers receive  free  of  postage  for  the  small  sum  of  Five  Dollars  a  quarterly  and  a  monthly 
periodical  of  the  highest  character,  containing  together  fifteen  kiindred  large  octavo  pages. 

No  efforts  will  be  spared  to  maintain  the  reputation  which  these  periodicals  have  so  long  enjoyed 
as  faithful  chroniclers  of  medical  progress,  useful,  if  not  indispensable,  to  every  member  of  the 
profession. 

[T^^  The  safest  mode  of  remittance  is  by  postal  money  order,  drawn  to  the  order  of  the  under- 
signed. Where  money  order  post-offices  are  not  accessible,  remittances  for  the  ".Journal"  may 
be  made  at  the  risk  of  the  publisher,  by  taking  the  postmaster's  certificate  of  the  inclosure  and 
forwar.ling  of  the  money.     Address, 

HENRY  C.  LEA,  Philadelphia,  Pa. 


Heney  C.  Lea's  Publications — (Dictionaries). 


5 


jyUNGLISON  {ROBLEF),  M.D., 

Proffissnr  of  Institutes  of  Medicine  in  Jefferson  Medical  Oollerj".,  Philadelxihia. 

MEDICAL   LEXICON;   A  Dictionary   op  Medical  Science:    Con- 
taining a  concise  explanation  of  the  va.rious  Subjects  and  Terms  of  Anatomy,  Physiology, 
Pathology,  Hygiene,  Therapeutics,  Pharmacology,  Pharmacy,  Surgery,  Obstetrics,  Medical 
Jurisprudence,  and  Dentistry.     Notices  of  Climate  and  of  Mineral  Waters;   Formulae  for" 
Officinal,  Empirical,  and  Dietetic  Preparations;  with  the  Accentuation  and  Etymolowy  of 
the  Terms,  and  the  French  and  other  Synonyraes ;  so  as  to  constitute  a  French  as  well  as 
English  Medical  Lexicon.    Thoroughly  Revised,  and  very  greatly  Modified  and  Augmented. 
In  one  very  large  and  handsome  royal  octavo  volume  of  104S  double-coluinned  page."!,  in 
small  type ;  strongly  done  up  in  extra  cloth,  $6  00  ;  leather,  rai.sed  bands,  $6  75. 
The  object  of  the  author  from  the  outset  has  not  been  to  make  the  work  a  mere  lexicon  or 
dictionary  of  terms,  but  to  aiford,  under  each,  a  condensed  view  of  its  various  medical  relations, 
and  thus  to  render  the  work  an  epitome  of  the  existing  condition  of  medical  science.     Startin" 
with  this  view,  the  immense  demand  which  has  existed  for  the  work  has  enabled  him,  in  repeated 
revisions,  to  augment  its  completeness  and  usefulness,  until  at  length  it  has  attained  the  position 
of  a  recognized  and  standard  authority  wherever  the  language  is  spoken.     The  mechanical  exe- 
cution of  this  edition  will  be  found  greatly  superior  to  that  of  previous  impressions.    By  enlarging 
the  size  of  the  volume  to  a  royal  octavo,  and  by  the  employment  of  a  small  but  clear  type,  on 
extra  fine  paper,  the  additions  have  been  incorporated  without  materially  increasing  the  bulk  of 
the  volume,  and  the  matter  of  two  or  three  ordinary  octavos  has  been  compressed  into  the  space 
of  one  not  unhandy  for  consultation  and  reference. 

It  is  undoubtedly  the  most  complete  and  useful 


It  would  be  a  work  of  supererogation  to  "bestow  a 
word  of  praise  upou  this  Lexicon.  We  can  only 
wonder  at  the  labor  expended,  for  whenever  we  refer 
to  its  pages  for  information  we  are  seldom  disap- 
pointed in  finding  all  we  desire,  whether  it  be  in  ac- 
centuation, etymology,  or  defluition  of  terms. — New 
York  Medical  Journal,  November,  186.5.   * 

It  would  be  mere  waste  of  words  in  us  to  express 
our  admiration  of  a  work  which  is  so  universally 
and  deservedly  appreciated.  The  most  admirable 
work  of  its  kind  in  the  English  language.  As  a  book 
of  reference  it  is  invaluable  to  the  medical  practi- 
tioner, and  in  every  instance  that  we  have  turned 
over  its  pages  for  informatlun  we  have  been  charmed 
by  the  clearness  of  language  and  the  accuracy  of 
detail  with  which  eacli  ahoauds-  We  can  most  cor- 
dialiy  and  confidently  cummeud  it  to  our  readers. — 
Glasgow  Medical  Journal,  January,  lS6ti. 

A  work  to  which  there  is  no  equal  in  the  English 
language. — Edinburgh  Medical  Journal. 

It  is  something  more  than  a  dictionary,  and  some- 
thing less  than  an  eucyclopjedia.  This  edition  of  the 
well-known  work  is  a  great  improvement  on  its  pre- 
decessors. The  book  is  one  of  the  very  few  of  which 
it  may  be  said  with  truth  that  every  medical  mau 
should  possess  it.— London  Medical  Times,  Aug.  26, 
lS6.i. 

Few  works  of  the  class  exhibit  a  grander  monument 
of  patient  research  and  of  scientific  lore.  The  extent 
of  the  sale  of  this  lexicon  is  sufficient  to  testify  to  its 
Tiefnlaess,  and  to  the  great  service  conferred  by  Dr. 
Eobley  DungUson  on  the  profession,  and  indeed  on 
other.s,  by  its  issue. — London  Lancet,  May  1.3,  186.5. 

The  old  edition,  wiiich  is  now  superseded  by  the 
new,  has  be'n  univer.-'aUy  looked  upon  by  tlie  medi- 
cal profession  as  a  work  of  immf-u.se  research  and 
great  value.  The  new  has  increased  usefulness;  for 
medicine,  in  all  its  branches,  has  been  making  such 
progress  that  many  new  terms  and  subjects  iiave  re- 
cently beea  introduced:  all  of  which  maybe  found 
fully  defined  in  the  present  edition.  We  kuow  of  no 
oiher  dictionary  in  the  English  language  that  can 
bear  a  comparison  with  it  in  point  of  completeness  of 
sabjects  and  accuracy  of  statement.— i\^.  Y.  Drug- 
gists'' Oircvlar,  186.'i. 

For  inany  years  Dunglison's  Dictionary  has  been 
the  standard  book  of  reference  with  most  practition- 
ers in  thiscountiy,  and  we  can  certainly  commend 


medical  dictiDuary  hitherto  published  in  this  country. 
— Chicago  Med.  Examiner,  February,  l,'r6.5. 

What  we  take  to  be  decidedly  the  best  medical  dic- 
tionary in  the  English  language.  The  present  edition 
is  brought  fully  up  to  the  advanced  state  of  science. 
For  many  a  long  year  "Duuglison"  has  been  at  our 
elbow,  a  constant  'companion  and  friend,  and  we 
greet  him  in  his  replenished  and  improved  form  with 
especial  satisfaction. — Paeijio  Med.  and  Surg.  Jov/r- 
nal,  June  27,  1865. 

Tins  is,  perhaps,  the  book  of  all  others  which  the 
physician  or  surgeon  should  have  on  his  shelves.  It 
is  more  needed  at  the  present  day  than  a  few  years 
back. — Canada  Med.  Journal,  July,  1865.  ' 

It  deservedly  stands  at  the  head,  and  cannot  be 
surpassed  in  excellence. — Buffalo  Med,  and  Surg. 
Joarnal,  April,  1865. 

We  can  sincerely  commend  Dr.  Dunglison's  work 
as  most  thorough,  scientific,  and  accurate.  We  have 
tested  it  by  searching  its  pages  for  new  terms,  which 
have  abounded  so  much  of  late  in  medical  nomen- 
clature, and  our  search  has  been  successful  in  every 
instance.  We  have  been  particular!}'  struck  with  the 
fulness  of  the  synonymy  and  the  accuracy  of  the  de- 
rivatioQ  of  words.  It  is  as  necessary  a  work  to  every 
enlightened  physician  as  Worcester's  English  Dic- 
tionary is  to  every  one  who  would  keep  up  his  know- 
ledge of  the  English  tongue  to  the  standard  of  the 
present  day.  It  is,  to  our  mind,  the  most  complete 
work  of  the  kind  with  which  we  are  acquainted. — 
Boston  Med.  and  Surg.  Journal,  June  22,  1865. 

We  are  free  to  confess  that  we  know  of  no  medical 
dictionary  more  complete;  no  one  better,  if  so  well 
adapted  for  the  u.se  of  the  student;  no  one  that  may 
be  consulted  with  more  satisfaction  by  the  medical 
practitioner. — Am.  Jour.  Med.  Sciences,  April,  1865. 

The  value  of  the  present  edition  has  been  greatly 
enhanced  by  the  introduction  of  new  subjects  and 
terms,  and  a  more  complete  etymology  and  accentua- 
tion, which  renders  the  work  not  ouly  satisfactory 
and  desirable,  but  indispensable  to  the  physician. — 
Chicago  Med.  Journal,  April,  186.5. 

No  intelligent  member  of  the  profession  can  or  will 
be  without  it. — St.  Louis  Med.  and  Surg.  Journal, 
April,  1835. 

It  has  the  rare  merit  that  it  certainly  has  no  rival 


this  work  to  the  renewed  confidence  and  regard  of  I  in  the  English  langua.'<e  for  accuracy  and  extent  of 
our  readers. — Cincinnati  Lancet,  April,  186.5.  I  reference-s. — London  Medical  Gazette. 


JJODLYN  [RICHARD  D.),  M.  D. 


A  DICTIOXARY  OF  THE  TERMR  USED  IN  MEDICINE  AND 

TJfE  COLLATERAL  SCIt'LMOES.  A  now  American  edition,  revised,  with  numerous 
a/ldition.a,  by  Lsaac  IIavk,  M.D.,  Editor  of  the  "American  Journal  of  the  Medical 
Sciencfc.s."  In  one  large  royal  12mo.  voiaine  of  over  500  double-columned  pages;  extra 
cloth,  -tl  50 ;  leather,  $2  00, 

It  io  the  be»t  book  of  definitionH  we  have,  and  ought  alwayn  to  be  npon  the  student's  t-A\>]n.— Southern 
3Itd.  and  Surg.  Journal. 


Henry  C.  Lea's  Publications — {Ifaimals). 


WEILL  [JO EN),  M.D., 


and      OMITH  {FRANCIS  G.),  M.  D., 

Prof,  of  the  Institutes  of  Medicine  in  the  Univ.  of  Penna. 


AN    ANALYTICAL    COMPENDIUM   OP   THE   VARIOUS 

BRANCHES  OF  MEDICAL  SCIENCE;  for  the  Use  and  Examination  of  Students.  A 
new  edition,  revised  and  improved.  In  one  very  large  and  handsomely  printed  royal  12mo. 
volume,  of  about  one  thousand  pages,  with  374  wood  cuts,  extra  cloth,  $4  ;  strongly  bound 
in  leather,  with  raised  bands,  $4  75. 


The  Compend  of  Drs.  Neill  and  Smith,  is  incompara- 
bly the  most  valuable  work  of  its  class  ever  published 
in  this  country.  Attempts  have  been  made  in  various 
quarters  to  squeeze  Anatomy.  Physiology,  Surgery, 
the  Practice  of  Medicine,  Obstetrics,  Materia  Medica, 
and  Qheniistry  into  a  single  manual;  but  the  opera- 
tion has  signally  failed  in  the  hands  of  all  up  to  the 
advent  of  "Neili  and  Smith's"  volume,  which  is  quite 
a  miracle  of  success.  The  outlines  of  the  whole  are 
admirably  drawn  and  illustrated,  and  the  authors 
are  emiaently  entitled  to  the  grateful  consideration 
of  the  student  of  every  class.— i\^.  0.  Med.  and  Surg. 
Journal. 

This  popular  favorite  with  the  student  is  so  well 
known  that  it  requires  no  more  at  the  hands  of  a 
medical  editor  thaa  the  annunciation  of  a  new  and 
improved  edition.  There  is  no  sort  of  comparison 
between  this  work  and  any  other  on  a  similar  plan, 
and  for  a  similar  object.— ivas/i.  Journ  of  Medieine. 

There  are  but  few  students  or  practitioners  of  me- 
dicine unacquainted  with  the  former  editions  of  this 
unassumiug  though  highly  instructive  work.  The 
whole  science  of  medicine  appears  to  have  been  sifted, 
as  the  gold-beariug  sands  of  El  Dorado,  and  the  pre- 
cious facts  treasured  up  in  this  little  volume.  A  cora- 
piete  portable  library  so  condensed  that  the  student 
may  make  it  his  constant  pocket  companion. —  West- 
ern Lancet. 

To  compress  the  whole  science  of  medicine  in  less 
than  1,000  pages  is  an  impossibility,  but  we  think  that 
the  book  before  us  approaches  as  near  to  it  as  is  pos- 
sible. Altogether,  it  is  the  best  of  its  class,  and  has 
met  with  a  deserved  success.  As  an  elementary  text- 
book for  students,  it  has  been  useful,  and  will  con- 
tinue to  be  employed  in  the  examination  of  private 
classes,  whilst  it  will  often  be  referred  to  by  the 
country  practitioner. —  Va.  Med.  Journal. 


As  a  handbook  for  students  it  is  invaluable,  con- 
taining in  the  most  condensed  form  the  established 
facts  and  principles  of  medicine  and  its  collateral 
sciences. — iV.  H  Journal  of  Iledicine. 

In  the  rapid  course  of  lectures,  where  work  for  the 
students  is  heavy,  and  review  necessary  for  an  exa- 
mination, a  compend  is  not  only  valuable,  but  it  is 
almost  a  sine  qua  non.  The  one  before  us  is,  in  most 
of  the  divisions,  the  most  unexceptionable  of  all  books 
of  the  kind  that  we  know  of.  The  newest  and  sound- 
est doctrines  and  the  latest  improvements  and  dis- 
coveries are  explicitly,  though  concisely,  laid  before 
the  student.  Of  course  it  is  useless  for  us  to  recom- 
mend it  to  all  last  course  students,  but  there  is  a  class 
to  whom  we  very  sincerely  commend  this  cheap  book 
as  worth  its  weight  in  silver — that  class  is  the  gradu- 
ates in  medicine  of  more  than  ten  yeai-s'  standing, 
who  have  not  studied  medicine  since.  They  will 
perhaps  And  out  from  it  that  the  science  is  not  e.K- 
actly  now  what  it  was  when  they  left  it  off.  —  The 
Stethoscope. 

Having  made  free  use  of  this  volume  in  our  exami- 
nations of  pupils,  we  can  speak  from  experience  in 
recommending  it  as  an  admii'ahle  compend  for  stu- 
dents, and  especially  useful  to  preceptors  who  exam- 
ine their  pupils.  It  will  save  the  teacher  much  labor 
by  enabling  hira  readily  to  recall  all  of  the  points 
upon  which  his  pupils  should  be  examined.  A  work 
of  this  sort  should  be  in  the  hands  of  every  one  who 
takes  pujiils  into  his  office  with  a  view  of  examiuiug 
them  ;  aud  this  is  unquesliouably  the  best  of  its  class. 
Let  every  practitioner  who  has  pupils  provide  himself 
with  it,  and  lie  will  find  the  labor  of  refreshing  his 
knowledge  so  much  facilitated  that  he  will  be  able  to 
do  justice  to  his  pupils  at  very  little  cost  of  time  or 
trouble  to  himself. — Transylvania  Med.  Journal. 


TVDLOW  {J.L.),  M.D., 

A   MANUAL   OF   EXAMINATIONS   upon   Anatomy,   Physiology, 

Surgery,  Practice  of  Medicine,  Obstetrics,  Materia  Medica,  Chemistry,  Phariiiacy,  and 
Therapeutics.  To  which  is  added  a  Medical  Formulary.  Third  edition,  thoroughly  revised 
and  greatly  extended  and  enlarged.  AYith  370  illustrations.  In  one  handsome  royal 
12mo.  volume  of  816  large  pages,  extra  cloth,  $3  25;  leather,  $3  75. 

The  arrangement  of  this  volume  in  the  form  of  question  and  answer  renders  it  especially  suit- 
able for  the  office  examination  of  students,  and  for  those  preparing  for  graduation. 


We  know  of  no  better  companion  for  the  student 
during  the  hours  spent  in  the  lecture-room,  or  to  re- 
fresh, at  a  glance,  his  memory  of  the  various  topics 
crammed  into  his  head  by  the  various  professors  to 
whom  be  is  compelled  to  listen. — Western  Lancet. 

As  it  embraces  the  whole  range  of  medical  studies 
it  is  necessarily  voluminous,  containing  S16  large 
duodecimo  pages.  After  a  somewhat  careful  exami- 
nation of  its  contents,  we  have  formed  a  much  more 
favorable  opinion  of  it  than  we  are  wont  to  regard 
such  works.  Although  well  adapted  to  meet  the  wants 


of  the  student  in  preparing  for  his  final  examination, 
it  might  be  profitably  consulted  by  the  practitioner 
also,  who  is  most  apt  to  become  rusty  in  the  very  kind 
of  details  here  given,  and  who,  amid  the  hurry  of  his 
daily  routine,  is  but  too  prone  to  neglect  the  study  of 
more  elaborate  works.  The  possession  ofva,  volume 
of  this  kind  might  serve  as  an  inducement  for  him  to 
seize  the  moment  of  excited  curiosity  to  inform  him- 
self on  any  subject,  and  which  is  otherwise  too  often 
allowed  to  pass  unimproved. — St.  Louis  Med.  and 
Surg.  Journal. 


rpANNER  {THOMAS  RAWKES),  M.  D., 

A  MANUAL  OF  CLINICAL  MEDICINE  AND  PHYSICAL  DIAG- 

NOSIS.  Third  American,  from  the  second  enlarged  and  revised  English  edition.  To 
which  is  added  The  Code  of  Ethics  of  the  American  Medical  Association.  In  one  hand- 
some volume  12mo.      {Preparing  for  early  publication.) 

This  work,  after  undergoing  a  very  thorough  revision  at  the  hands  of  the  author,  may  now  be 
expected  to  appear  shortly.  The  title  scarcely  affords  a  proper  idea  of  the  range  of  subjects  em- 
braced in  the  volume,  as  it  contains  not  only  very  full  details  of  diagnostic  symptoms  properly 
classified,  but  also  a  large  amount  of  information  on  matters  of  every  day^practical  importance, 
not  usually  touched  upon  in  the.  systematic  works,  or  scattered  through  many  different  volumes. 


Henry  C.  Lea's  Publications — (Anatomy).  T 

ffRAF  {HENRY),  F.  R.  S., 

^^  Lecturer  on  Anatomy  at  St.  Qaorg&'s  Hospttal,  London. 

ANATOMY,    DESCRIPTIVE    AND    SURGICAL.      The  Drawings  by 

H.  V.  Carter,  M.  D.,  late  Demonstrator  on  Anatomy  at  St.  George's  Hospital ;  the  Dissec- 
tions jointly  by  the  Author  and  Dr.  Carter.     Second  American,  from  the  second  revised 
and  improved  London  edition.     In  one  magnificent  imperial  octavo  volume,  of  over  8(10 
pages,  vfith  .388  large  and  elaborate  engravings  on  TFOod.     Price  in  extra  cloth,  $6  00  ; 
leather,  raised  bands,  $7  CO. 
The  author  has  endeavored  in  this  work  to  cover  a  more  extended  range  of  subjects  than  is  cus- 
tomary in  the  ordinary  text-books,  by  giving  not  only  the  details  necessary  for  the  student,  but 
also  the  application  of  those  details  in  the  practice  of  medicine  and  surgery,  thus  rendering  it  both 
a  guide  tor  the  learner,  and  an  admirable  work  of  reference  for  the  active  practitioner.     The  en- 
gravings form  a  special  feature  in  the  work,  many  of  them  being  the  size  of  nature,  nearly  all 
original,  and  having  the  names  of  the  various  parts  printed  on  the  body  of  the  cut,  in  place  of 
figures  of  reference,  with  descriptions  at  the  foot.     They  thus  form  a  complete  and  splendid  series, 
which  will  greatly  assist  the  student  in  obtaining  a  clear  idea  of  Anatomy,  and  will  also  serve  to 
refresh  the  memory  of  those  who  may  find  in  the  exigencies  of  practice  the  necessity  of  recalling 
the  details  of  the  dissecting  room;  while  combining,  as  it  does,  a  complete  Athis  of  Anatomy,  with 
a  thorough  treatise  on  systematic,  descriptive,  and  applied  Anatomy,  the  work  will  be  found  of 
essentiiil  use  to  all  physicians  who  receive  students  in  their  offices,  relieving  both  preceptor  and 
pupil  of  much  labor  in  laying  the  groundwork  of  a  thorough  medical  education. 

Notwithstanding  its  exceedingly  low  price,  the  work  will  be  found,  in  every  detail  of  mechanical 
execution,  one  of  the  handsomest  that  has  yet  been  ofl'ered  to  the  American  profession ;  while  the 
careful  scrutiny  of  a  competent  anatomist  has  relieved  it  of  whatever  typographical  errors  existed 
in  the  English  edition. 

Thus  it  is  that  hook  after  book  makes  the  labor  of  1  and  with  scarce  a  reference  to  the  printed  test.  The 
the  student  ea.siev  thau  before,  and  siace  we  have  surgical  application  of  the  various  regions  i.s  also  pre- 
seen  IBlanchard  &  Lea's  new  edition  of  Gray's  Ana-  ]  sented  with  force  and  clearness,  impie.ssing  upon  the 
tomy,  certainly  the  fine.st  work  of  the  kind  now  ex- 
tant", we  would  fain  hope  that  the  bugbear  of  medical 
students  will  lose  half  its  horrors,  and  this  necessary 
foundation  of  physiological  science  will  be  much  fa- 
cilitated and  advanced. — N.  0.  Med.  News. 

The  various  points  illustrated  are  max-ked  directly 
on  the  structure ;  that  is,  wliether  it  be  muscle,  pro- 
cess, artery,  nerve,  valve,  etc.  etc. — we  say  each  point 
is  distinctly  marked  by  lettered  engravings,  so  that 
the  student  perceives  at  once  each  point  descrHied  as 
readily  as  if  pointed  out  on  the  subject  by  We  de- 
monstrator. Most  of  the  illustrations  are  thus  ren- 
dered exceedingly  satisfactory,  and  to  the  physician 
they  serve  to  refresh  the  memory  with  great  readiness 


student  at  each  step  of  his  research  all  the  important 
relaiions  of  the  structure  demonstrated. — Cincinnati 
Lancet. 

This  is,  we  believe,  the  handsomest  book  on  Ana- 
tomy as  yet  published  in  our  language,  and  bids  fair 
to  become  in  a  short  time  thr  standard  text-book  of 
our  colleges  and  studies.  Students  and  practitioners 
will  alike  appreciate  this  book.  We  predict  for  it  a 
bright  career,  and  are  fully  prepared  to  endorse  the 
statement  of  the  London  Lancet,  that  "We  are  not 
acquainted  with  any  work  in  any  language  which 
can  take  equal  rank  with  the  one  before  us."  Paper, 
printing,  binding,  all  are  excellent,  and  we  feel  that 
a  grateful  profession  will  not  allow  the  publishers  to 
go  unrewarded. — Nashville  Med.  and  Surg.  Journal. 


QMITH  {HENRY H.),  3I.D.,         and     TJORNER  (  WILLIAM  E.),  M.D., 

Prof,  of  Surgery  in  the  Univ.  of  Penna.,  &c.  LateProf.  of  Anatomij  in  the  Univ.  of  Penna.,  &o- 

AN    ANATOMICAL    ATLAS,   illustrative   of  the   Structure  of  the 

Human  Body.     In  one  volume,  large  imperial  octavo,  extra  cloth,  with  about  six  hundred 

and  fifty  beautiful  figures.     $4  50. 
The  plan  nf  this  Arias,  which  renders  it  so  peou-  I  the  kind  that  has  yet  appeared;  and  we  must  add, 
liaily  convenient  for  the  student,  and  its  superb  ar-  |  the  very  beautiful  manner  in  which  it  is  "got  up" 
tistical  execution,  have  been  already  p-)inted  out.  We  I  is  so  creditable  to  the  country  as  to  be  flattering  to 
must  congratulate  the  student  upon  the  completiou     our  national  pride— ^4?»«-icfMi  Medical  Jovrnal. 
of  this  Atlas,  as  it  is  the  most  convenient  work  of  I 


JJORNER  {WILLIA31  E.),  M.D., 

SPECIAL  ANATOMY  AND  HISTOLOGY.  Eighth  edition,  exten- 
sively revised  and  modified.  In  two  large  octavo  volumes  of  over  1000  pages,  with  more 
than  300  wood-cuts;  extra  cloth,  $6  00.  * 

OHARPEY  ( WILLIAM),  M.D.,      and       Q  VAIN  {JONES  Sf  RICHARD). 
HUMAN  ANATOMY.   Revised,  with  Notes  and  Additions,  by  Joseph 

Luii>Y,  M.D.,  Professor  of  Anatomy  in  the  Universit.y  of  Pennsylvania.     Complete  in  two 
large  octavo  volumes,  of  about  L^OO  pages,  with  511  illustra.tions ;   e.itra  cloth,  $6  00. 
The  very  low  price  of  this  standard  work,  and  its  completeness  in  all  departments  of  the  subject, 
should  command  for  it  a  place  in  the  library  of  all  anatomical  students. 


ALLEN-  {J.  M.),  M.D. 
THE  PRACTICAL  ANATOMIST;  or.  The  Student's  Guide  m  tiik 

DisHKCTiNfi  KoOM.     With  2(H)  illustrations.     In  one  very  handsome  royal  12mo.  volume, 
of  over  600  pages;  extra  cloth,  $2  00. 
One  of  the  most  DHeful  works  njioii  the  subject  ever  wriltei  —Mcdi'nl  Jixaminer. 


Henry  C.  Lea's  Publicatioxs — (Anatomy). 


JYILSON  [EEAS31US),  F.E.S. 


A  SYSTEM  OF  HUMAN  ANATOMY,  General  and  Special.     A  new 

and  revised  American,  from  the  last  and  enlarged  English  edition.     Edited  by  "W.  H.  Go- 
BRECHT,  M.  D.,  Professor  of  General  and  Surgical  Anatomy  in  the  Medical  College  of  Ohio. 
Illusti-ated  with  three  hundred  and  ninety-seven  engravings  on  wood.     In  one  large  and 
handsome  octavo  volume,  of  over  600  large  pages;  extra  cloth,  $4  00;  leather,  $5  00. 
The  publisher  trusts  that  the  well-earned  reputation  of  this  long-established  favorite  will  be 
more  than  maintained  by  the  present  edition.     Besides  a  very  thorough  revision  by  the  author,  it 
has  been  most  carefully  examined  by  the  editor,  and  the  efforts  of  both  have  been  directed  to  in- 
troducing everything  which  increased  experience  in  its  use  has  suggested  as  desirable  to  render  it 
a  complete  text-book  for  those  seeking  to  obtain  or  to  renew  an  acquaintance  with  Human  Ana- 
tomy.    The  amount  of  additions  which  it  has  thus  received  may  be  estimated  from  the  fact  that 
the  present  edition  contains  over  one-fourth  more  matter  than  the  last,  rendering  a  smaller  type 
and  an  enlarged  page  requisite  to  keep  the  volume  within  a  convenient  size.     The  author  has  not 
only  thus  added  largely  to  the  work,  but  he  has  also  made  alterations  throughout,  wherever  there 
appeared  the  opportunity  of  improving  the  arrangement  or  style,  so  as  to  present  every  fact  in  its 
most  appropriate  manner,  and  to  render  the  whole  as  clear  and  intelligible  as  possible.    The  editor 
has  exercised  the  utmost  caution  to  obtain  entire  accuracy  in  the  text,  and  has  largely  increased 
the  number  of  illustrations,  of  which  there  are  about  one  hundred  and  fifty  more  in  this  edition 
than  in  the  last,  thus  bringing  distinctly  before  the  eye  of  the  student  everything  of  interest  or 
importance. 

The  publisher  has  felt  that  neither  care  nor  expense  should  be  spared  to  render  the  external 
finish  of  the  volume  worthy  of  the  universal  favor  with  which  it  has  been  received  by  the  American 
profession,  and  he  has  endeavored,  consequently,  to  produce  in  its  mechanical  execution  an  im- 
provement coyresponding  with  that  which  the  text  has  enjoyed.  It  will  therefore  be  found  one  of 
the  handsomest  specimens  of  typography  as  yet  produced  in  this  country,  and  in  all  respects  suited 
to  the  ofBce  table  of  the  practitioner,  notwithstanding  the  exceedingly  low  price  at  which  it  has 
been  placed. 


TDT  THE  SA3UB  AVTHOU.      ■ 

THE  DISSECTOR'S   MANUAL;   or,  Practical  and  Surgical  Ana- 

T03IY.  Third  American,  from  the  last  revised  and  enlarged  English  edition.  Modified  and 
rearranged  by  William  Huxt,  M.  D.,  late  Demonstrator  of  Anatomy  in  the  Unive\-sity  of 
Pennsylvania.  In  one  large  and  handsome  royal  12mo.  volume,  of  582  pages,  v-fith  154 
illustrations;  extra  cloth,     $2  GO. 


ACLISE  {JOSEPH). 
"SUPvGICAL  ANATOMY.     By  Joseph  Maclise,  Snrgeon.    In  one 

volume,  very  large  imperial  quarto;  with  fiS  large  and  splendid  plates,  drawn  in  the  best 
style  and  beautifully  colored,  containing  190  figures,  many  of  them  the  size  of  life;  together 
with  copious  explanatory  letter-press.      Strongly  and  handsomely  bound  in  extra  cloth. 
Price  $14  00. 
As  no  complete  work  of  the  kind  has  heretofore  been  published  in  the  English  language,  the 
present  volume  will  supply  a  want  long  felt  in  this  country  of  an  accurate  and  comprehensive 
Atlas  of  Surgical  Anatomy,  to  which  the  student  and  practitioner  can  at  all  times  refer  to  ascer- 
tain the  exact  relative  positions  of  the  various  portions  of  the  human  frame  towards  each  other 
and  to  the  surface,  as  well  as  their  abnormal  deviations.     The  importance  of  such  a  work  to  the 
student,  in  the  absence  of  anatomical  material,  and  to  practitioners,   either  for  consultation  in 
emergencies  or  to  refresh  their  recollections  of  the  dissecting  room,  is  evident.     Notwithstanding 
the  large  size,  beauty  and  finish  of  the  very  numerous  illustrations,  it  will  be  observed  that  the 
price  is  so  low  as  to  place  it  within  the  reach  of  all  members  of  the  profession. 


We  know  of  no  work  on  surgical  anatomy  which 
can  compete  wltli  it. — Lancet. 

The  work  of  Maclise  on  surgical  anatomy  is  of  the 
highest  value.  In  some  respects  it  is  the  best  publi- 
c-ttion  of  its  kind  we  have  seen,  and  is  worthy  of  a 
place  in  the  libiary  of  any  medical  man,  while  the 
student  could  scarcely  make  a  belter  investment  than 
this. — The  Western  Journal  of  Medicine  and  Surgery. 

Kg  such  lithogi-aphic  illustrations  of  surgical  re- 
gions have  hitherto,  we  think,  been  given.  While 
the  operator  is  shown  every  vessel  aud  nerve  where 
an  operation  is  contemplated,  the  exact  anatomist  is 


refreshed  by  those  clear  and  distinct  dissections, 
which  every  one  mast  appreciate  wlio  has  a  pai'ticle 
of  enthusiasm.  The  English  medical  press  has  quite 
exhausted  tiie  words  of  praise,  in  recommending  this 
admirable  treatise.  Those  who  have  any  curiosity 
to  gratify,  in  reference  to  the  perfectibility  of  the 
lithographic  art  in  delineating  the  complex  mechan- 
ism of  the  human  body,  are  invited  to  examine  our 
specimen  copy.  If  anything  will  induce  surgeons 
and  students  to  patronize  a  book  of  such  rare  value 
aud  everyday  importance  to  them,  it  will  be  a  survey 
of  the  artistical  skill  exhibited  in  these  fac-simiies  of 
nature. — Boston  2ftd.  and  Surg.  Journal. 


pEASLEE  {E.B.),  M.D., 

Professor  of  Anatomy  arid  Physiology  in  Dartraouth  Med.  College,  N.  H. 

HUMAN  HISTOLOGY,  in  its  relations  to  Anatomj',  Phj'-siology,  and 

Pathology ;  for  the  use  of  medical  students.     With  four  hundred  and  thirty-four  illustra- 
tions.    In  one  handsome  octavo  volume  of  over  600  pages,  extra  cloth.     $3  75. 


We  would  recommend  it  as  containing  a  summary 
of  all  tliat  is  known  of  the  important  subjects  which 
it  treats:  of  all  that  is  in  the  great  works  of  Simim 
and  Lehraann,  and  the  organic  chemists  in  general. 
Master  this  one  volume,  aad  you  know  all  that  is 


known  of  the  great  fundamental  principle.s  of  medi- 
cine, aud  we  have  no  hesitation  in  saying  that  it  is 
an  hi>nor  to  the  American  medical  profession. — 
fit.  Louis  Med.  and  Surg.  Journal. 


Henry  C.  Lea's  Publications — (Physiology). 


riARPENTER  [WILLIAM  B.),  M.D.,  F.R.S., 

Exaininer  in  Physiology  and  Ocimparativa  Anatomy  in  the  University  of  London. 

PRINCIPLES  OF  HUMAN  PIIYSIOLOGS-Y ;  with  their  chief  appli- 

cations  to  Psychology,  Pathology,  Therapeutics,  Hygiene  and.  Forensic  Medicine.  A  new- 
American  from  the  last  and  revised  London  edition.  With  nearly  three  hundred  illustration.?. 
Edited,  with  additions,  by  Francis  Gukney  Smith,  M.  D.,  Professor  of  the  Institutes  of 
Medicine  in  the  University  of  Pennsylvania,  &c.  In  one  very  large  and  beautiful  octavo 
volume,  of  about  900  large  pages,  handsomely  printed ;  extra  cloth,  $5  50  ;  leather,  raised 
bands,  $6  50. 


The  liighest  compliment  that  can  be  extended  to 
this  great  work  of  Dr.  Carpenter  is  to  call  attention 
to  this,  another  new  edition,  which  the  favorable 
regard  of  the  profession  has  called  f  )r.  Carpenter  is 
the  standard  authority  on  physiology,  and  no  physi- 
cian or  medical  student  will  regard  his  library  as 
complete  without  a  copy  of  it. — Cincinnati  Med.  Ob- 
server. 

With  Dr.  Smith,  we  confidently  believe  "that  the 
present  will  more  than  sustain  the  enviable  reputa- 
tion already  attained  by  former  editions,  of  being 
one  of  the  fullest  and  most  complete  treatises  on  the 
subject  in  the  Engli.sb  language."  We  know  of  none 
from  the  pages  of  which  a  satisfactory  knowledge  of 
the  physiology  of  the  human  organlura  can  be  as  well 
obtained,  none  better  adapted  for  the  use  of  such  as 
take  up  the  study  of  physiology  in  its  reference  to 
the  institutes  and  practice  of  medicine. — Am.  Jov/r. 
Med.  Sciences. 

A  complete  cyclopajdia  of  this  branch  of  science.— 
N.  ¥.  Med.  Times. 


We  doubt  not  it  is  destined  to  retain  a  strong  hold 
on  public  favor,  and  remain  the  favorite  text-book  in. 
our  colleges. — Virginia  Medical  Joiornal. 

We  have  so  often  spoken  in  terms  of  high  com- 
mendation of  Dr.  Carpenter's  elaborate  work  on  hu- 
man physiology  that,  in  announcing  a  new  edition, 
it  is  unneoessMry  to  add  anything  to  what  has  hereto- 
fore been  said,  and  especially  is  this  the  case  since 
every  intelli.gent  physician  is  as  well  aware  of  the 
character  and  merits  of  the  work  as  we  our.selves  are. 
— St.  Louis  Med.  and  Surg.  Journal. 

The  above  is  the  title  of  what  is  emphatically  tt« 
great  work  on  physiology ;  and  we  are  conscious  that 
it  would  be  a  useless  etfort  to  attempt  to  add  any- 
thing to  the  reputation  of  this  invaluable  work,  and 
can  only  say  to  all  with  whom  our  opinion  has  any 
influence,  that  it  is  our  authority. — Atlanta  Med. 
Journal. 

The  greatest,  the  most  reliable,  and  the  best  book 
on  the  subject  which  we  know  of  in  the  English  lan- 
guage. — Stethoscope. 


T  THE  SAME  AUTHOR. 


E 

PRINCIPLES  OP  COMPARATIYE  PHYSIOLOGY.    New  Ameri- 

can,  from  the  Fourth  and  Pv.evi.<ed  London  Edition.     In  one  large  and  handsome  octavo 
volume,  with  over  three  hundred  beautiful  illustrations      Pp.752.    Extra  cloth,  $5  00. 
As  a  complete  and  condensed  treatise  on  its  extended  and  important  subject,  this  work  becomes 

a  necessity  to  students  of  natural  science,  while  the  A'ery  low  price  at  which  it  is  offered  places  it 

within  the  reach  of  all. 


B 


Y  THE  SAME  A  UTHOR. 

THE  MICROSCOPE  AND  ITS  REYELATIONS.    With  an  Appen- 

dix  containing  the  Applications  of  the  Micro.^cope  to  Clinical  Medicine,  ka.  By  F.  Gr. 
SiriTH  M.  D.  Illustrated  by  four  hundred  and  thirty-four  beautiful  engravings  on  wood. 
In  one  large  and  very  handsome  octavo  volume,  of  724  pages,  extra  cloth,  $5  25. 


rpODD  [ROBERT  B.),  M.D.  F.R.S., 


and 


'no  WMAN  [  W.),  F.  R.  S. 


THE    PHYSIOLOGICAL   ANATOMY  AND   PHYSIOLOGY   OF 

MAISr.     With  about  three  hundred  large  and  beautiful  illustrations  on  wood.     Complete  in 
one  large  octavo  volume  of  950  pages,  extra  cloth.     Price  §4  75. 


The  names  of  Todd  and  Bowman  have  long  been 
familiar  to  the  student  of  physiology.  In  this  work 
we  have  the  ripe  experience  of  these  laborious  physi- 
ologists on  every  branch  of  this  science.  They  gave 
each  i-ubject  the  most  thorough  and  critical  examina- 
tion before  making  it  a  matter  of  record.  Thus,  while 
they  advanced  tardily,  apparently,  in  their  publica- 
tion, the  work  thus  issued  was  a  complete  exponent 
of  the  science  of  physiology  at  the  time  of  its  final 
appearance.  We  can,  therefore,  recnmmend  this 
Work  as  one  of  the  most  reliable  which  the  student  or 


practitioner  can  onnsult  relating  to  physiology. — .y. 
Y.  Journal  of  3Iedicine. 

To  it  the  rising  generation  of  medical  men  will 
owe,  in  great  measure,  a  familiar  acquaintance  with 
all  the  chief  truths  respecting  the  healthy  structure 
and  working  of  the  frames  which  are  to  form  the 
subject  of  their  care  The  possession  of  such  know- 
ledge will  do  more  fo  make  sound  and  able  practi- 
tioners than  anything  else. — British  and  Foreign 
Madico-  Chir  urg  ical  Review. 


iriRKES  [  WILLIAM  SENHO  USE],  M.  D.,  ^ 

A  MANUAL  OF  PHYSIOLOGY.     A  new  American  from  the  third 

and  improved  London  edition      With  two  hundred  illustrations.     In  one  large  and  hand- 
Bome  royal  12mo.  volume.     Pp.  58R.     Extra  cloth,  $2  25  ;  leather,  $2  75. 
By  the  u.se  of  a  fine  and  clear  type,  a  very  large  amount  of  matter  has  been  condensed  into  a 
comparatively  small  volume,   and  at  its  exceedingly  low  price  it  will  be  found  a  most  desirable 
manual  for  students  or  for  gentlemen  desirous  to  refresh  their  knowledge  of  modern  physiology. 

lent  guide  in  the  study  of  physiology  in  its  most  ad- 
vanced and  perfect  form,  fho  autlior  has  sliowa 
himself  Ciipable  of  giving  details  snfficiently  ample 


It  is  at  once  convenient  in  size,  comprehensive  In 
design,  and  conci«e  in  statement,  and  altogether  well 
adapted  for  the  purpose  designed. — St.  Louui  Med. 
an/1  Surg.  Jouraal. 

The  phy.siological  reader  will  find  it  a  most  excel- 


in  a  condensed  and  concentrated  shape,  on  a  scie)ice 
in  which  it  Is  neces.sary  at  once  to  bo  correct  and  not 
lengthened.— Erfin'-'wr-^/i  Med.  and  Swrg.  Journal. 


10 


Henry  C.  Lea's  Publications — {Physiology). 


D 


ALTON  [J.  C),  M.D., 

Professor  of  Physiology  in  the  GoUege  of  Physicians  and  Surgeons,  New  YorTi,  &c. 

A  TREATISE  ON  HUMAN  PHYSIOLOGY,  Designed  for  the  use 

of  students  and  Practitioners  of  Medicine.  Third  edition,  revi-ed,  with  nearly  three  hun- 
dred illustrations  on  wood.  In  one  very  beautiful  octavo  volume,  of  700  pages,  extra  cloth, 
$5  25  ;  leather,  $6  25. 

"  In  the  present  edition  of  this  work  the  general  plan  and  arrangement  of  the  two  former  ones 
are  retained.  The  improvements  and  additions  which  have  been  introduced  consist  in  the  incor- 
poration into  the  text  of  certain  new  facts  and  discoveries,  relating  mainly  to  details,  which  have 
made  their  appearance  within  the  last  three  years." — Author's  Prpface. 

The  rapid  demand  for  another  edition  of  this  work  sufficiently  shows  that  the  author  has  suc- 
ceeded in  his  efforts  to  produce  a  text-book  of  standard  and  permanent  value,  embodying  within 
a  moderate  compass  all  that  is  definitively  and  positively  known  within  the  domain  of  Human 
Physiology.  His  high  reputation  as  an  original  observer  and  investigator  is  a  guarantee  that  in 
again  revising  it  he  has  introduced  whatever  is  necessary  to  render  it  thoroughly  on  a  level  with 
the  advanced  science  of  the  day,  and  this  has  been  accomplished  without  unduly  increasing  tha 
size  of  the  volume. 

No  exertion  has  been  spared  to  maintain  the  standard  of  typographical  execution  which  has 
rendered  this  work  admittedly  one  of  the  handsomest  volumes  as  yet  produced  in  this  country. 


We  lielieve  we  fully  recognize  the  value  of  Draper 
and  Dunglison,  Carpenter  and  Kirkes,  and  Todd  and 
Bowman,  and  yet  we  unhesitatingly  place  Dalton  at 
the  head  of  the  list,  for  qualities  already  enumerated. 
In  the  important  feature  of  illustration,  Dalton' s  work 
is  without  a  peer,  either  in  adaptedness  to  the  text, 
simplicity  and  graphicness  of  design,  or  elegance  of 
artistic  execution. — Chicago  Med.  Examiner. 

In  calling  attention  to  the  recent  publication  of  the 
third  edition  of  this  hook,  it  will  only  be  necessary 
to  say  that  it  retains  all  the  merits  and  essentially  the 
same  plan  of  the  two  former  editions,  with  which 
every  American  student  of  medicine  is  undoubtedly 
familiar  The  distinguished  author  has  added  to  the 
text  all  the  importaut  discoveries  in  experimental 
physiology  and  embryology  which  have  appeared 
during  the  last  three  years. — Boston  3Ied.  and  Surg. 
Journal,  June  30,  ISOi. 

The  arrangement  of  the  work  is  excellent.     The 
facts  and  theories  put  forward  in  it  are  brought  up  to 
the  present  tiriio.     Indeed,  it  may  be  looked  upon  as 
prespntiug  the  latest  views  of  physiologists  in  a  con- 
dehsed  fonn,  written  in  a  clear,  distinct  manner,  and  : 
in  a  style  which  maizes  it  not  only  a  book  of  study 
to  the  student,  or  of  reference  to  the  medical  practi-  j 
tioner,  but  a  book  which  may  be  taken  up  and  read  ' 
with  both  pleasure  and  profit  at  any  time. — Canada  j 
Med.  Journal,  October,  ISG-l.  | 

In  Dr.  Dalton's  excellent  treatise  we  have  one  of 
the  latest  contributions  of  our  American  brethren  to  j 
medical  science,  and  its  popularity  may  be  estimated 
by  the  fact  that  this,  the  second  edition,  follows  upon 
the  first  with  the  short  interval  of  two  years.  The  \ 
author  has  succeeded  in  giving  his  readers  an  exceed-  j 
ingly  accurate  and  at  the  same  time  most  readable  I 


resumi  of  the  present  condition  of  physiological 
science  ;  and,  moreover,  he  has  not  been  content  with 
mere  compilation,  but  has  ably  investigM.ted  the  func- 
tions of  the  body  for  himself,  many  of  the  original 
experiments  and  observations  being  of  the  greatest 
value. — London  Med.  Review. 

This  work,  recognized  as  a  standard  text-book  by 
the  medical  schools,  and  with  which  the  members  of 
the  profes.sion  are  so  familiar,  demands  but  a  brieX 
notice.  Its  popularity  is  attested  by  the  rapidity 
with  which  former  editions  have  been  exhausted. — 
Chicago  Med.  Journal,  April,  186-1. 

To  the  student  of  physiology,  no  work  as  yet  pub- 
lished could  be  more  satisfactory  as  a  guide,  not  only 
to  a  correct  knowledge  of  the  physiological  subjects 
embraced  in  its  limits,  but,  what  is  of  far  greater 
Importance,  it  will  prove  the  best  teacher  of  the  modes 
of  investigation  by  which  that  knowledge  can  be 
acquired,  and,  if  necessary,  tested. — The  Golumhus 
UeoiKio  of  Med.  and  Surgery. 

Until  within  a  very  recent  date,  American  works 
on  phy.siology  were  almost  entirely  unknown  in  E-t\- 
rope,  a  circum.stance  solely  due  to  the  fact  of  their 
being  little  else  than  crude  compilations  of  Europeaa 
works;  Within  the  last  few  years,  however,  a  great 
change  has  taken  place  for  the  better,  and  our  friends 
on  the  other  side  of  the  Atlantic  can  now  boast  of 
possessing  manuals  equalled  by  few  and  excelled  by 
none  of  our  own.  In  Dr.  Daltou's  treatise  we  are  , 
glad  to  Bud  a  valuable  addition  to  physiological  lite- 
rature. With  pleasure  we  have  observed  throag-hout 
the  volume  proof  of  the  author  not  being  a  mere 
compiler  of  the  ideas  of  others,  but  an  active  laborer 
in  the  field  of  science. — The  Brit,  and  For.  Medico- 
Ohirurgical  Revieu). 


jyUNGLISON  [ROBLEY),  M.D., 

Professor  of  Institutes  of  Medicine  in  Jefferson  Medical  College,  Philadelphia. 

HUMAN  PHYSIOLOGY.     Eighth  edition.     Thoroughly  revised  and 

extensively  modified  and  enlarged,  with  five  hundred  and  thirty-two  illustrations.     In  two 
large  and  handsomely  printed  octavo  volumes  of  about  1500  pages,  extra  cloth.     $7  00. 


TEHMANN  {G. 


G.) 


B 


PHYSIOLOGICAL  CHEMISTRY.  Translated  from  the  second  edi- 
tion by  George  B.  Day,  M.  D.,  F.  R.  S.,  &c.,  edited  by  R.  E.  Rogers,  M.  D.,  Professor  of 
Chemistry  in  the  Medical  Department  of  the  University  of  Pennsylvania,  with  illustrations 
selected  from  Funke's  Atlas  of  Physiological  Chemistry,  and  an  Appendix  of  plates.  Com- 
plete in  two  large  and  handsome  octavo  volumes,  containing  1200  pages,  with  nearly  two 
hundred  illustrations,  extra  cloth.     $6  00. 

Y  THE  SAME  AUTHOR.  

MANUAL  OP   CHEMICAL  PHYSIOLOGY.     Translated  from  the 

German,  with  Notes  and  Additions,  by  J  Cheston  Morris,  M.  D.,  with  an  Introductory 
Essay  on  Vital  Force,  by  Professor  Samuel  Jackson,  M.  D.,  of  the  University  of  Pennsyl- 
vania. With  illustrations  on  wo^d.  In  one  very  handsome  octavo  volume  of  336  pages, 
extra  cloth.     $2  25. 


Hknry  C.  Lea's  Publications — {Chemistry). 


11 


-DRANDE  ( WM.  T.] 


D.  C.L.,  and    rTAYLOR  [ALFRED  S.),  M.D.,  F.R.S. 

CHEMISTRY.    In  one  handsome  8vo.  vol.  of  G96  pp.,  extra  clotli.   $4  50. 

The  passage  of  this  volume  through  the  press  has  been  superintended  by  a  competent  chemist 
who  has  sedulously  endeavored  to  secure  the  accuracy  so  essential  to  a  work  of  this  nature.  No 
additions  have  been  made,  but  the  publishers  have  been  favored  by  the  authors  with  some  correc- 
tions and  revisions  of  the  first  twenty-one  chapters,  which  have  been  duly  inserted. 

A  most  comprehensive  aud  compact  volume.     Its   |  the  clearest,  autl  most  practical  tliat  can  be  i)ut  in  the 


information  is  recent,  aud  is  conveyed  in  clear  lan- 
guage. Its  index  of  sixty  closely-printed  columns 
shows  with  what  cai-e  new  discoveries  have  been 
added  to  well-known  facts. — The  Chemical  Neios. 

The  Handbook  in  Chemistry  op  the  Student. — 
For  clearness  of  language,  accuracy  of  descrijition, 
e.xtent  of  information,  and  freedom  from  pedantry 
and  mysticism,  no  other  text-book  comes  into  com- 
petition with  it. — The  Lancet. 

The  authors  set  out  with  the  definite  purpose  of 
writing  a  book  which  shall  he  intelligihle  to  any 
educated  man.  Thus  conceived,  and  worked  out  in 
the  most  sturdy,  common-sense  method,  this  book 
gives  in  the  clearest  and  most  summary  method 
possible*aU  the  facts  and  doctrines  of  chemistry. — 
Medical  Times. 

We  can  cordially  recommend  this  work  as  one  of 


hands  of  the  student. — Edinburgh  Med.  Journal. 

It  abounds  in  innumerable  interestiug  facts  not  to 
be  found  elsewhere;  and  from  the  rnas'erly  manner 
in  which  every  subject  is  handled,  with  its  pleasing 
mode  of  describing  even  the  dryest  details,  it  cannot 
fail  to  prove  acceptable,  not  only  to  those  for  whom 
it  is  intended,  but  to  the  profession  at  large. — Canada 
Lancet. 

We  have  for  a  long  time  felt  that  the  preparation 
of  a  proper  chemical  text-book  for  students  would 
be  time  better  spent  than  in  the  invention  of  a  novel 
system  of  classification  or  the  discovery  of  half  a 
dozen  new  elements  ending  in  iura.  We  believe  this 
want  has  at  last  been  satisfied  in  the  book  now  before 
us,  which  has  been  prepared  expressly  for  medical 
students  by  two  of  the  most  experienced  teachers  of 
the  science  iu  England. — Boston  Med.  and  Surgical 
Journal. 


no  WMAN  {JOHN  E.) ,  M.  D. 


PRACTICAL  HANDBOOK  OP  MEDICAL  CHEMISTRY.    Edited 

by  C.  L.  Bloxam,  Professor  of  Practical  Chemistry  in  King's  College,  London.  Fourth 
American,  from  the  fourth  and  revised  English  Edition.  In  one  neat  volume,  royal  12mo., 
pp.  351,  with  numerous  illustrations,  extra  cloth.     $2  25. 


The  fourth  edition  of  this  invaluable  text-book  of 
Medical  Chemistry  was  published  in  Ens^laud  in  Octo- 
ber of  the  last  year.  The  Editor  has  brought  down 
the  Handbook  to  that  date,  introducing,  as  far  as  was 
compatible  with  the  necessary  conciseness  of  such  a 
■work,  all  the  valuable  discoveries  in  the  science 
■which  have  come  to  light  since  the  previous  edition 
was  printed.  The  work  is  indispensable  to  every 
student  of  medicine  or  enlightened  practitioner.  It 
is  printed  in  clear  type,  and  the  illustrations  are 
numerous  and  intelligible. — Boston  Mtd.  and  Surg. 
Journal. 


The  medical  studeut  and  practitioner  have  already 
appreciated  properly  this  small  manual,  in  which 
instruction  for  the  examination  aud  analysis  of  the 
urine,  blood  and  uther  animal  products,  both  healthy 
and  morbid,  are  accurately  given.  The  directions 
for  the  detection  of  poisons  in  organic  mixtures  and 
in  the  tissues  are  exceedingly  well  exposed  in  a  con- 
cise and  simple  manner.  This  fourth  edition  has 
been  thoroughly  revised  by  the  editor,  and  brought 
up  to  the  present  state  of  practical  medical  chemistry. 
— Pacific  Med.  and  Surg.  Journal. 


B 


Y  TEE  SA3IE  AUTHOR. 


INTRODUCTION  TO   PRACTICAL  CHEMISTRY,  INCLTIDINa 

ANALYSIS.     Third  American,  from  the  third  and  revised  London  edition.     With  numer- 
ous illustrations.     In  one  neat  vol.,  royal  ]2mo.,  extra  cloth.     $2  25. 
One  of  the  most  complete  manuals  that  has  for  a  |  very  judiciously  simplified  his  subjects  and  illustra- 


long    time  been 
AthencEwm. 


given    to   the    medical    student. — 


We  regard  it  as  realizing  almost  everything  to  be 
desired  iu  an  introduction  to  Practical  Chemistry. 
It  is  by  far  the  best  adapted  for  the  Chemical  student 
of  any  that  has  yet  fallen  in  onr  way. — British  and 
Foreign  Medico-Chirv.rgical  Review. 

The  best  introductory  work  on  the  subject  with 
■which  we  are  acquainted. — Edinburgh  Monthly  Jo^hr. 

This  little  treatise,  or  manual,  is  designed  espe- 
cially for  beginners.    With  this  view  the  author  has 


tions  as  much  as  possible,  and  presents  all  of  th" 
details  pei-tainiog  to  chemical  analysis,  and  other 
portions  difficult  for  beginners  to  comprehend,  ia 
such  a  clear  aud  distinct  manner  as  to  remove  all 
doubt  or  difiiculty.  Thus  a  subject  which  is  usually 
regarded  by  students  as  almost  beyond  their  com- 
prehension, is  rendered  very  easy  of  acquisition. 
Several  valuable  tal>les,  a  glossary,  etc.,  all  combine 
to  render  the  work  peculiarly  adapted  to  the  wants 
of  such;  aud  as  such  we  commend  it  to  them. — The 
Western  Lancet. 


QRA HAM  ( THOMAS),  F.  R.  S. 


THE   ELEMENTS   OF   INORGANIC   CHEMISTRY,  including  the 

jApplications  of  the  Science  in  the  Arts.  New  and  much  enlarged  edition,  by  IIenry 
Watt.s  and  PvObkrt  Biiidges,  M.  D.  Complete  in  one  large  and  handsome  octavo  volume, 
of  over  800  very  large  pages,  with  two  hundred  and  thirty-two  wood-cuts,  extra  cloth. 
$5  50. 

Part  II,,  comjjleting  the  work  from  p.  4.S1  to  end,  with  Index,  Title  Matter,  kc,  may  be  had 
separate,  cloth  backs  and  paper  sides.     Price  $3  00. 


Prr/m  Prof.  E.  N.  Horsfurd,  Harvard  College. 

It  han,  io  ItH  earlier  and  less  perfect  editions,  been 
familiar  to  me,  and  tlie  excellence  of  its  plan  and 
the  cleariienB  aud  completeness  of  its  discussions, 
have  long  been  my  admiration. 

Wo  reader  of  English  works  on  this  science  can 


afford  to  be  without  this  edition  of  Prof.  Graham's 
Elements. — Silliman'H  Jov,rnal,  March,  IS.'iS. 

From  Prof.  Wolcott  Olhbs,  N.  Y.  Free  Academy. 

The  work  is  an  admirable  one  in  all  respects,  and 
its  repiililication  here  cannot  fail  to  exert  a  positive 
iniluence  upon  the  progress  of  science  in  this  country. 


12         Henry  C.  Lea's  Publications — {Chemistry  and  Pharmacy). 

pOWNES  [GEORGE],  Ph.D. 

A  MANUAL  OF  ELEMENTARY  CHEMISTRY;   Theoretical  and 

Practical.    With  one  hundred  and  ninety-seven  illustrations.    Edited  by  E,obbrt  Bridges, 
M.  D.     In  one  large  royal  12mo.  volume,  of  600  pages,  extra  cloth,  $2  00  ;  leather,  $2  60. 


We  know  of  no  treatise  in  the  language  so  well 
calculated  to  aid  the  student  in  becoming  familiar 
with  the  numerous  facts  in  the  intrinsic  science  on 
which  it  treats,  or  one  better  calculated  as  a  text- 
book for  those  attending  Chemical  lectures.  *  f  *  * 
The  best  text-book  on  Chemistry  that  has  issued  from 
our  pi-ess. — American  Medical  Journal. 

We  again  most  cheerfully  recommend  it  as  the 
best  texVbook  for  students  in  attendance  upon  Chem- 
ical lectures  that  we  have  yet  examined. — III.  and 
Ind.  Med.  and  Surg.  Journal. 

A  first-rate  work  upon  a  first-rate  subject. — St. 
Louis  Med.  and  Surg.  Journal. 

jS'o  manual  of  Chemistry  which  we  have  met 
comes  so  near  meeting  the  wants  of  the  beginner.  — 
Western  -Journal  of  Medicine  and  Surgery. 


We  know  of  none  within  the  same  limits  which 
has  higher  claims  to  our  confidence  as  a  college  class- 
book,  both  for  accnracy  of  detail  and  scientific  ar- 
rangement.— Augusta  Medical  Journal. 

We  know  of  no  text-book  on  chemistry  that  we 
would  sooner  recommend  to  the  student  than  this 
edition  of  Prof.  Fownes'  work. — Montreal  Medical 
Chronicle. 

A  new  and  revised  edition  of  one  of  the  best  elemen- 
tary works  on  chemistry  accessible  to  the  American 
and  English  student. — N.  Y.  Joxirnal  of  Medical  and 
Collateral  Science. 

We  unhesitatingly  recommend  it  to  medical  stu- 
dents.— N.  W.  Med.  and  Surg.  Journal. 

This  is  a  most  excellent  text-book  for  cla.ss  instruc- 
tion in  chemistry,  whether  for  schools  or  colleges. — 
Silli'inan's  Journal. 


ABEL  AND  BLOXAM'S  HANDBOOK  OF  CHEMIS- 
TllY,  Tlieoretical,  Practical,  and  Technical.  With 
a  recommendatory  Preface,  by  Dr.  Hoffman.  In 
one  large  octavo  volume  of  t)62  pages,  with  illus- 
trations, extra  cloth,  $i  50. 

GARDINfEirS  MEDICAL  CHEMISTRY,  for  the  Use  of 
Students,  and  the  Profession.  In  one  royal  12mo. 
volume,  with  wood-cuts;  pp.  396,  extra  cloth, 
$1  00. 


KWAPP'S  TECHNOLOGY  ;  or  Ohemlstry  Applied  to 
the  Arts,  and  to  Manufactures.  Edited,  with 
numerous  notes  and  additions,  by  Dr.  Edmund 
EoKALS,  and  Dr.  Thomas  Plichardso.^.  With  Amer- 
ican additions,  by  Prof.  Walter  R  Johnson.  la 
two  very  handsome  octavo  volumes,  containing 
about  1000  pages,  and  300  wood  engravings,  extra 
cloth,  $6  00. 


pARRISH  {ED  WARD), 

Professor  of  Materia  Medico  in  the  Philadelphia  College  of  Pharmacy. 

A  TREATISE  ON  PHARMACY.     Designed  as  a  Text-Book  for  the 

Student,  and  as  a  Guide  for  the  Physician  and  Pharmaceutist.  With  many  Formulae  and 
Prescriptions.  Third  Edition,  greatly  improved.  In  one  handsome  octavo  volume,  of  850 
pages,  with  several  hundred  illustrations,  extra  cloth.     $5  00. 

The  rapid  progress  made  in  the  science  and  art  of  Pharmacy,  and  the  many  changes  in  the  last 
edition  of  the  Pharmacopoeia  have  required  a  very  thorough  revision  of  this  work  to  render  it 
worthy  the  continued  conlidence  with  which  it  has  heretofore  been  favored.  In  effecting  this, 
many  portions  have  been  condensed,  and  every  eifort  has  been  made  to  avoid  increasing  unduly 
the  bulk  of  the  volume,  yet,  notwithstanding  this,  it  will  be  found  enlarged  by  about  one  hundred 
and  fifty  pages.  The  author's  aim  has  been  to  present  in  a  clear  and  compendious  manner  every- 
thing of  value  to  the  prescriber  and  dispenser  of  medicines,  and  the  work,  it  is  hoped,  will  be  found 
more  than  ever  a  complete  book  of  reference  and  text-book,  indispensable  to  all  who  desire  to  keep 
on  a  level  with  the  advance  of  knowledge  connected  with  tbeir  profession. 

The  immense  amount  of  practical  information  condensed  in  its  pages  may  be  estimated  from 
the  fact  that  the  Index  contains  about  4700  items.  Under  the  head  of  Acids  there  are  312  refer- 
ences ;  under  Emplastrum,  3ti ;  Extracts,  159 ;  Lozenges,  25  ;  Mixtures,  55  ;  Pills,  66  ;  Syrups, 
131 ;  Tinctures,  138 ;  Unguentum,  57,  &c. 


We  have  examined  this  large  volume  with  a  good 
deal  of  care,  and  find  that  the  author  has  completely 
exhausted  the  subject  upon  which  he  treats  ;  a  more 
complete  work,  we  think,  it  would  be  impossible  to 
find.  To  the  student  of  pharmacy  the  work  is  indis- 
pensable ;  indeed,  so  far  as  we  know,  it  is  the  only  one 
of  its  kind  in  exi.stence,  and  eveu  to  the  physician  or 
medical  student  who  can  spare  five  dollars  to  pur- 
chase it,  we  feel  sure  the  practical  information  he 
will  obtain  will  more  than  compensate  him  for  the 
outlay. — Canada  Med.  Journal,  Nov.  lS6i. 

The  medical  student  and  the  practising  physician 
will  find  the  volume  of  inestimable  worth  for  study 
and  reference. — San  Francisco  Med.  Press,  July, 
1S6I. 

When  we  .say  that  this  book  is  in  some  respects 
the  best  which  has  been  published  ou  the  subject  in 
the  English  language  for  a  great  many  years,  we  do 
not  wish  it  to  be  understood  as  very  extravagant 
Ijraise.  In  truth,  it  is  not  so  much  the  best  as  the 
only  book. — The  London  Chemical  News. 

An  attempt  to  furnish  anything  like  an  analysis  of 
Parrish's  very  valuable  and  elaborate  Treatise  on 
Practical  Pharmacy  would  require  more  space  than 
we  have  at  our  disposal.  This,  however,  is  not  so 
much  a  iBatter  of  regret,  inasmuch  as  it  would  be 
difiicult  to  think  of  any  point,  however  minute  and 
apparently  trivial,  connected  with  the  manipulation 
of  pharmaceutic  substances  or  appliances  which  has 


not  been  clearly  and  carefully  discussed  in  this  vol- 
ume. Want  of  space  prevents  our  enlarging  further 
on  this  valuable  work,  and  we  must  conclude  by  a 
simiile  expression  of  our  hearty  appreciation  of  its 
merits. — Dublin  Quarterly  Jour,  of  Medical  Science, 
August,  1861. 

We  have  in  this  able  aud  elaborate  work  a  fair  ex- 
position of  pharmaceutical  science  as  it  exists  in  the 
United  States  ;  and  it  shows  that  our  transatlantic 
friends  have  given  the  subject  most  elaborate  con- 
sideration, and  have  brought  their  art  to  a  degree  of 
perfection  which,  we  believe,  is  scarcely  to  be  sur- 
passed anywhere.  The  book  is,  of  course,  of  more 
direct  value  to  the  medicine  maker  than  to  the  physi- 
cian ;  yet  Mr.  PARRtsH  has  not  failed  to  introduce 
matter  in  which  the  prescriber  is  Cjuite  as  much 
interested  as  the  compounder  of  remedies.  In  con- 
clusion, we  can  only  express  our  high  opinion  of  the 
value  of  this  work  as  a  guide  to  the  pharmaceutist, 
and  in  many  respects  to  the  physician,  not  only  ia 
America,  but  in  other  parts  of  the  world. — British 
3Ied.  Journal,  Nov.  12th,  1861. 

The  former  editions  have  been  suflSciently  long 
before  the  medical  public  to  render  the  merits  of  the 
work  well  known.  It  is  certainly  one  of  the  most 
complete  and  valuable  works  on  practical  pharmacy 
to  which  the  student,  the  practitioner,  or  the  apothe- 
cary can  have  access. — Chicago  Medical  Examiner, 
March,  1861. 


Henry  C.  Lea's  Publications — {Materia  Med.  and  Therapeutic^^).      13 

pRIFFITH  {ROBERT  E.),  M.D. 

A  UNIVERSAL  FORMULARY,   Containing  the  Methods  of  Pre- 

paring  and  Administering  Officinal  and  other  Medicines.     The  whole  adapted  to  Physicians 
and  Pharmaceutists.     Second  edition,   thoroughly  revised,  with  numerous  additions,  by 
Robert  P.  Thomas,   M.D.,  Professor  of  Materia  Medica  in  the  Philadelphia  College  of 
Pharmacy.     In  one  large  and  handsome   octavo  volume  of  650  pages,   double-columns. 
Extra  cloth,  $4  00 ;  leather,  $5  00. 
In  this  volume,  the  Formulary  proper  occupies  over  400  double-column  pages,   and  contains 
about  .5000  formulas,  among  which,  besides  those  strictly  medical,  vrill  be  found  numerous  valuable 
receipts  for  the  preparation  of  essences,  perfumes,  inks,  soaps,  varnishes,  &c.  ko,.     In  addition  to 
this,  the  work  contains  a  vast  amount  of  information  indispensable  for  daily  reference  by  the  prac- 
tising physician  and  apothecary,  embracing  Tables  of  Weights  and  Measures,  Specific  Gravity, 
Temperature  for  Pharmaceutical  Operations,  Hydrometrical  Equivalents,  Specific  Gravities  of  some 
of  the  Preparations  of  the  Pharmacoposias,  Relation  between  different  Therm ometrical  Scales, 
Explanation  of  Abbreviations  used  in  Formula?,  Vocabulary  of  Words  used  in  Prescriptions,  Ob- 
servations on  the  Management  of  the  Sick  Room,  Doses  of  Medicines,  Rules  for  the  Administration 
of  Medicines,  Management  of  Convalescence  and  Relapses,.  Dietetic  Preparations  not  included  in 
the  Formulary,  List  of  Incompatibles,  Posological  Table,  Table  of  Pharmaceutical  Names  which 
differ  in  the  Pharmacopoeias,  Oflicinal  Preparations  and  Directions,  and  Poisons. 

Three  complete  and  extended  Indexes  render  the  work  especially  adapted  for  immediate  consul- 
tation. One,  of  Diseases  and  their  Remedies,  presents  under  the  head  of  each  disease  the 
remedial  agents  which  have  been  usefully  exhibited  in  it,  with  reference  to  the  formula  containing 
them — while  another  of  Pharmaceutical  and  Botajstical  Names,  and  a  very  thorough  Gexeral 
Index  afford  the  means  of  obtaining  at  once  any  information  desired.  The  Formulary  itself  is 
arranged  alphabetically,  under  the  heads  of  the  leading  constituents  of  the  prescriptions. 


This  is  one  of  tlie  most  nseful  books  for  the  prac- 
tising physician  which  has  been  is'^ued  from  the  press 
of  late  years,  containing  a  vast  variety  of  formulas 
for  the  safe  and  convenient  administration  of  medi- 
cines, all  arranged  upon  scientific  and  rational  prin- 
ciples, with  the  quantifies  stated  in  full,  without 
signs  or  abbreviations. — Memphis  Med.  Recorder. 


We  know  of  none  in  our  language,  or  any  other,  so 
comprehensive  ia  its  details. — London  Lancet. 

One  of  the  most  complete  works  of  the  kind  in  any 
language. — Edinburgh  Sled.  Journal. 

We  are  not  cognizant  of  the  esistence  of  a  parallel 
work. — London  Med.  Guzette. 


fyTILLE  [ALFRED),  M.  D., 

Professor  of  Theory  mid  Practice  of  Medicine  in  the  University  of  Penna. 

THERAPEUTICS  AND  MATERIA  MEDICA;  a  Systematic  Treatise 

on  the  Action  and  Uses  of  Medicinal  Agents,   including  their  Description  and  History. 

Second  edition,  revised  and  enlarged.     In  two  large  and  handsome  octavo  volumes,  of  1592 

pages.     Extra  cloth,  $10  00;    leather,  raised  bands,  $12  00. 

Dr.  Stille's  splendid  work  on  therapeutics  and  ma-  I      We  have  placed  first  on  the  list  Dr.  Stille's  great 

teria  medica. — London  Med.  Times,  April  8,  1865.        |  work  on  therapeutics. — Edinburgh  Med.  Journ.,  1S65. 


E 


LLIS  (BENJAMIN),  M.D. 

THE  MEDICAL  FORMULARY:  being  a  Collection  of  Prescriptions 

derived  from  the  writings  and  practice  of  many  of  tlie  most  eminent  physicians  of  America 
and  Europe.  Together  with  the  usual  Dietetic  Preparations  and  Antidotes  for  Poisons.  To 
which  is  added  an  Appendix,  on  the  Endermic  use  of  Medicines,  and  on  the  use  of  Ether 
and  Chloroform.  The  whole  accompanied  with  a  few  brief  Pharmaceutic  and  Medical  Ob- 
servations. Eleventh  edition,  carefully  revised  and  much  extended  by  Robert  P.  TnoiiAS, 
M.  D.,  Professor  of  Materia  Medica  in  the  Philadelphia  College  of  Pharmacy.  In  one 
volume  8vo.,  of  about  350  pages.     $3  00. 

frequently  noticed  in  this  Journal  as  the  successive 
editions  appeared,  that  it  is  sufficient,  on  the  present 
occasion,  to  state  that  the  editor  has  introduced  into 
the  eleventh  edition  a  large  amount  of  new  matter, 
derived  from  the  current  medical  and  pharmaceutical 
works,  as  well  as  a  number  of  valuable  prescriptions 
furnished  from  private  sources.  A  very  comprehen- 
sive and  extremely  useful  index  has  also  been  .sup- 
plied, which  facilitates  reference  to  the  particular 
article  the  prescriber  may  wish  to  administer;  and 
the  language  of  the  Formulary  has  been  made  to  coi-:- 
respond  wilh  the  nomenclature  of  the  new  national 
Pharmacopoeia. — Am.  Jour.  Med.  Sciences,  Jan.  186i. 


We  endorse  the  favorable  opinion  which  the  book 
has  so  long  established  for  itself,  and  take  this  occa- 
sion to  commend  it  to  our  readers  as  one  of  the  con- 
venient handbooks  of  the  office  and  library. — Cin- 
einnati  Lancet,  Feb.  1861. 


The  work  has  long  been  before  the  profession,  and 
its  merits  are  well  known.  The  present  edition  con- 
tains many  valuable  additions,  and  will  be  found  to 
be  an  exceedingly  convpnieut  and  useful  volume  for 
reference  by  the  medical  practitioner.  —  Chicago 
IM.ical  Examinf.r,  March,  18(54:. 

The  work  is  now  so  well  known,  and  has  been  so 


jyVNGLISON  {ROBLEY),  31. D., 

Professor  of  Tnntittde,g  of  Medicine  in  Jefferson  Medical  College,  PhiladelpJiia. 

GENERAL  THERAPEUTICS  AND  MATERIA  MEDICA;  adapted 

for  a  Medical  Text-Book.     AVith  Indexes  of  Remedies  and  of  Diseases  and  their  Remedies. 
Sixth  edition,  revised  nnd  improved.    With  one  hundred  and  ninety-three  illustrations.    In 
two  large  and  hand.somefy  printed  octavo  vols,  of  about  1100  pages,  extra  cloth.     $6  50. 
Tjr  T/i-E  SAME  AUTHOR.  

NEW  REMEDIES,  WITH  FORMULA  FOR  THEIR  PREPARA- 
TION AND  ADMINISTRATION.  Seventh  edition,  with  extensive  additions.  In  one 
very  large  octavo  volume  of  770  pages,  extra  cloth.     $4  00. 


14      Henry  C.  Lea's  Publications — {Materia  Med.  and  Tliey^apeutics). 

JJEREIRA  [JONATHAN),  M.D.,  F.R.S.  and  L.S. 

MATERIA   MEDICA   AIS^D  THERAPEUTICS;   being  an  AMdg- 

ment  of  the  late  Dr.  Pereira's  Elements  of  Materia  Meclica,  arranged  in  conformity  with 
the  British  Pharmacoposia,  and  adnpted  to  the  use  of  Medical  Practitioners,  Chemists  and 
Druggists,   Medical  and  Pharmaceutical   Students,  &c.     By  F.  J.  Farre,  M.D.,   Senior 
Physician  to  St.  Bartholomew's  Hospital,  and  London  Editor  of  the  British  Pharmacopoeia; 
assisted  by  Robert  Bentley,  M.R.C.S.,  Professor  of  Materia  Medica  and  Botany  to  the 
Pharmaceutical  Society  of  Great  Britain;  and  by  Robert  Warington,  P.R.S.,  Chemical 
Operator  to  the  Society  of  Apothecaries.     With  numerous  additions  and  references  to  the 
United  States  Pharmacopoeia,  by  Horatio  C.  Wood,  M.D.,  Professor  of  Botany  in  the 
University  of  Pennsylvania.       In  one  large  and  handsome   octavo  volume  of  over  1000 
closely  printed  pages,  V7ith  236  illustrations,  extra  cloth,  $7  00  ;  leather,  raised  bands,  $8  00. 
{Now  Ready.) 
The  very  large  size  attained  by  the  great  work  of  Dr.  Pereira,  in  its  successive  revisions,  has 
seemed  to  render  desirable  an  abridgment  of  it  in  which  should  be  omitted  the  commercial  and 
physical  details  which  possessed  more  interest  for  the  druggist  than  for  the  practitioner.     In  the 
effort  at  condensation,  however,  the  English  editors  have  confined  the  work  almost  wholly  to  the 
articles  embraced  in  the  British  Pharmacopoeia,  thus  omitting  much  that  is  of  primary  importance 
to  the  American  practitioner.     The  aim  of  Professor  Wood  has  been  to  restore   from  Pereira's 
original  work  whatever  may  seem  necessary,  and  to  add  notices  of  such  American  remedies  as 
claim  a  place  in  a  volume  designed  alike' for  the  student  and  physician.     In  this,  he  has  had  the 
advantage  of  the  valuable  notes  of  the  former  American  editor.  Professor  Carson,  and  his  additions 
will  be  found  to  constitute  from  one-fourth  to  one-third  of  the  whole  work.     Their  importance 
may  be  estimated  from  the  fact  that  he  has  introduced  notices  of  nearly  one  hundred  articles  not 
alluded  to  in  the  English  edition,  among  which  will  b^  found  detailed  accounts  of  such  remedies 
as  Bismuthi  Sub-Nitras,  Monsell's  Salt,  Pyro-Phosphate  of  Iron,  Iodide  of  Lead,  Glauber  Salts, 
Cyanide   of   Mercury,    Pepsin,    Prunus  Virgini.ma,   Eupatorium,   Veratrum  Viride,   Apocynum, 
Tapioca,  Arrow-Root,  Sago,  Euphorbium,  Helleborus,  Coffee,  Spigelia,  Salix,  Rhus,  Rubus,  Ca- 
labar Bean,  Succinium,  etc.  etc.     The  series  of  illustrations  has  been  largely  increased,  and  the 
object  of  the  work  will  be  to  present  a  thorough  and  condensed  view  of  the  whole  subject  in  its 
most  modern  aspect. 


Of  the  many  works  on  Materia  Medica  which  have 
appeared  since  Ihe  issuing  of  the  British  Phaimaco- 
poeia,  none  will  he  more  acceptable  to  the  student 
and  practitioner  than  the  present.     Pereira's  JIateria 


tions  of  his  predeces.sor's  great  work.  That  Dr.  Farre 
has  spared  no  endeavor  to  perform  his  task  in  every 
department,  in  the  most  perfect  manner,  may  he  al- 
ready inferred  from  the  fact  of  his  having  associated 


Medica  had  long  ago  asserted  for  itself  the  position  of  ,  with  himself  in  the  work,  the  two  distinguished  gen- 
being  the  most  complete  work  on  the  subject  in  the  !  tlemea  tvhose  names  appear  with  his  own  upon  the 


English  language.  But  its  very  completeness  stood 
in  the  way  of  its  success.  Except  in  the  way  of  refer- 
ence, or  to  tho-^e  who  made  a  special  stndy  of  Materia 
Medica,  Dr.  Pereira's  work  was  too  full,  and  its  pe- 
rusal required  an  amonnt  of  time  which  few  had  at 
their  disposal.  Dr  Farrehas  very  judiciously  availed 
himself  of  the  opportunity  of  the  publication  of  the 
new  Pharmacopoeia,  by  bringing  out  an  abridged  edi- 
tion of  the  great  work.  This  edition  of  Pereira  is  by 
BO  means  a  mere  abridged  re-issue,  but  contains  ma- 
ny improvements,  both  in  the  descriptive  and  thera- 
peutical departments.  We  can  recommend  it  as  a 
very  excellent  and  reliable  text-book. — Edinburgh 
Med  Journal,  February,  1S66. 

Dr.  Farre  has  conferred  on  both  students  and  prac- 
titioners a  real  boon  in  presenting  in  a  comprehensive 
form,  and  within  the  limits  of  a  moderate  octavo 
volume,  the  more  important  and  more  practical  por- 


title-page. — Dahlia  Quarterly  Journal,  May,  1S66. 

With  their  able  co-operation  he  has  succeeded  not 
only  in  reducin.g  Dr.  Pereira's  work  to  a  convenient 
size,  but  in  producing  a  very  reliable  and  instructive 
work  on  the  authorized  British  Materia  Medica. — 
British  Ilfedical  Journal,  December  2,  1S65. 

Only  f)92  pages,  while  Pereira's  oi-iginal  volumes 
included  2000,  and  yet  the  results  of  many  years'  ad- 
ditional research  in  pharmacology  and  therapeutics 
are  embodied  in  the  new  edition.  Unquestionably 
Dr.  Farre  has  conferred  a  great  benefit  upon  medical 
students  and  practitioners.  And  in  both  respects  we 
think  he  has  acted  very  judiciously.  And  the  worli 
is  now  condensed — brouglit  fully  into  accordance  with 
the  pharmacological  opinions  in  vogue,  and  can  be 
used  with  .great  advantage  as  a  handbook  for  exami- 
nations.— The  Lancet,  December,  1S65. 


p ARSON  [JOSEPH],  M.D.. 

^  Professor  of  Materia  Medica  and  Plmrrnacy  in  the  University  of  Pennsylvania,  &c. 

SYNOPSIS  OF  THE   COURSE   OF   LECTURES   ON  MATERIA 

MEDICA  AND  PHARMACY,  delivered  in  the  University  of  Pennsylvania.  With  three 
Lectures  on  the  Modus  Operandi  of  Medicines.  Third  edition,  revised.  In  one  handsome 
octavo  volume.     $2  60. 


EOVLE'S  MATERIA  MEDICA  AND  THERAPEU- 
TICS; including  the  Prepai-atious  of  the  Pharma- 
copoeias of  Londou,  Edinburgh,  Dublin,  and  of  the 
United  States.  With  many  new  medicines.  Edited 
by  .Joseph  Carsox,  M  D.  With  ninety-eight  illus- 
trations. In  one  large  octavo  volume  of  about  700 
pages,  exti'a  cloth.     $3  00. 

CHEISTISON'S  DISPENSATORY;  or,  Commentary 
on  the  Pharmacopoeias  of  Great  Britain  and  the 
United  States;  comprising  the  Natural  History, 
Description,  Chemistry,  Pharmacj',  Actions,  Uses, 
and  Doses  of  the  Articles  of  the  Materia  Medica. 
Second  edition,  revised  and  improved,  with  a  Sup- 
plement containing  the  most  important  New  Reme- 
dies. With  copious  additions,  and  two  hundred 
and  thirteen  large  wood-engravings.  By  R.  E<4LE.s- 
FKLD  Griffith,  5i.  D.  In  one  very  handsome  octavo 
volume  of  over  1000  pages,  extra  cloth.     $4  00. 


CARPENTER'S    PRIZE    ESSAY   ON   THE   USE  OF 

ALCOHOLtC  LkJOORS  IK  HEALTH  AND  DISEASE.      ^e-VT 

edition,  with  a  Preface  by  D.  F.  Condie,  M.D.,  and 
explanations  of  scientific  words.  In  one  neat  12mo. 
volume,  pp.  178,  extra  cloth.     60  cents. 

BEALE  ON  THE  LAWS  OF  HEALTH  IN  RELATION 
TO  JIiND  AND  Body.  In  one  vol.  royal  12mo.,  extra 
cloth,     pp.  296.     SO  cents. 

De  JONGH  on  the  THREE  KINDS  OF  COD-LIVER 
Oil,  with  their  Chemical  and  Therapeutic  Pro- 
perties.    1  vol.  12mo.,  cloth.     75  cents. 

MAYNE'S  DISPENSATORY  AND  THERAPEUTICAL 
Eemkmbrancer.  With  every  Practical^  Formula 
contained  in  the  three  British  Pharm'acopKias. 
Edited,  with  the  addition  of  the  Formulse  of  the 
U.  S.  Pharmacopceia,  by  R.  E.  Griffith,  M.  D.  In 
one  12mo.  volume,  300  pp.,  extra  cloth.     7o  cents. 


Henry  C.  Lea's  Publications — (Pathology). 


15 


ffROSS  (SAMUEL  D.),  M.  D., 

Prnfc.sfior  of  S\i,rgery  in  the  Jefferson  Medical  College  of  Philadelphia. 

ELEMENTS    OF    PATHOLOGICAL   ANATOMY.     Third    edition, 

thoroughly  revised  and  greatly  improved.     In  one  large  and  very  handsome  octavo  volume 
of  nearly  800  pages,  with  aliout  three  hundred  and  fifty  beautiful  illustrations,  of  which  a 
large  number  are  from  original  drawings  ;    extra  cloth.     $4  GO. 
The  very  beautiful  execution  of  this  valuable  work,  and  the  exceedingly  low  jirice  at  which  it 
is  offered,  should  command  for  it  a  place  in  the  library  of  every  practitioner. 

To  the  stuflent  of  medicine  we  would  say  that  we 
know  of  no  work  which  we  can  more  heartily  com- 
mend than  Gross's  Pathological  Anatomy. — Southern 


Med^  and  Sure/.  Journal. 

The  volume  commends  itself  to  the  medical  student ; 
it  will  repay  a  careful  perusal,  and  should  be  upon 


thebook-shelf  of  every  American  physician. — Qlwr  leg- 
ion Med.  Journal. 

It  contains  much  new  matter,  and  brings  down  our 
knowledge  of  pathology  to  the  latest  period. — London 
La,nctt. 


TONES  [G.  HANDFIELD),  F.R.S.,  and  SIEVEKING  [ED'.  H.),  M.D., 


AssiMant  Physioin.ns  and  Lecturers  in  St.  Mary^s  Hospital. 

A  MANUAL  OF   PATHOLOGICAL  ANATOMY.     First  American 

edition,  revised.     With  three  hundred  and  ninety- seven  handsome  wood  engravings.     In 
one  large  and  beautifully  printed  octavo  volume  of  nearly  760  pages,  extra  cloth,  S3  50. 


Our  limited  space  alone  restrains  us  from  noticing 
more  at  length  the  various  subjects  treated  of  in 
this  interesting  work;  presenting,  as  it  does,  an  excel- 
lent summarj'  of  the  existing  stale  of  knowledge  in 
relation  to  pathological  anatomy,  we  cannor  too 
strongly  urge  upon  the  student  the  necessity  of  a  tho- 
rough acquaintance  with  its  contents. — Medical  Ex- 
ananer. 

We  have  long  had  need  of  a  hand-book  of  patholo- 
gical anatomy  which  should  thoroughly  reflect  the 
present  state  of  that  science.  In  the  tre-itise  before 
us  this  desideratum  is  supplied  Within  the  limits  of 
a  moderate  octavo,  we  have  the  outlines  of  this  great 
department  of  medical  science  accurately   defined, 


and  tlie  most  recent  investigations  presented  in  suffi- 
cient detail  for  the  student  of  pathology.  We  cannot 
at  this  time  undertake  a  formal  analysis  of  this  trea- 
tise, as  it  would  involve  a  sepiirate  and  lengthy 
consideration  of  nearly  every  subject  discussed  ;  uor 
would  such  analysis  be  advantageous  to  the  medical 
reader.  The  work  is  of  sucli  a  character  that  every 
physician  ought  to  obtain  it,  both  for  reference  and 
study. — N.  Y.  Journal  of  Medicine. 

Its  importance  to  the  physician  cannot  be  too  highly 
estimated,  and  we  would  recommend  our  readers  to 
add  it  to  their  library  as  soon  as  tliey  conveniently 
can. — Montreal  Med.  Ohronicle. 


JDOKITANSKY  [CARL),  3LD., 

Curator  of  the  I'lnperial  Pathological  Museum,  a.nd  Professor  at  the  University  of  Vienna. 

A   MANUAL    OF   PATHOLOGICAL   ANATOMY.      Translated  by 

W.  E.  SwAiNE,  Edward  Sieveking,  C.  H.  Moore,  and  G.  E.  Day.    Four  volumes  octavo, 
bound  in  two,  of  about  1200  pages,  extra  cloth.     $7  50. 


GLUGE'S  ATLAS  OF  PATHOLOGICAL  HISTOLOGY. 
Translated,  with  Notes  and  Additions,  by  Joseph 
Leidt,  M.  D.     In  one  volume,  very  large  imperial  I 
quarto,   with   .320  copper-plate   figures,  plain. and 
colored,  extra  cloth.     $100.  I 


SIMON'S  GENERAL  PATHOLOGY,  as  conducive  to 
the  Establishment  of  Rational  Principles  for  the 
Prevention  and  Cure  of  Disease.  In  one  octavo 
volume  of  212  pages,  extra  cloth.     $1  25. 


y^lLLIAMS  [CHARLES  J.  B.),  M.D., 

Professor  of  Clinical  Medicine  in  University  College,  London, 

PRINCIPLES  OF  MEDICINE.     An  Elementary  Yiew  of  the  Causes, 

Nature,  Treatment,  Diagnosis,  and  Prognosis  of  Disease ;  with  brief  remarks  on  Hygienics, 
or  the  preservation  of  health.  A  new  Ainerican,  from  the  third  and  revised  London  edition. 
In  one  octavo  volume  of  about  500  pages,  extra  cloth.     $.3  50. 


The  unequivocal  favor  with  which  this  work  has 
been  received  by  the  profession,  both  in  Europe  and 
America,  is  one  among  the  many  gratifying  evidences 
which  might  be  adduced  as  going  to  show  that  there 
is  a  steady  progress  taking  place  in  the  science  as  well 
as  in  the  art  of  medicine. — St.  Louis  Med.  and  Surg. 
Journal. 

No  work  has  ever  achieved  or  maintained  a  more 
deserved  reputation.  —  Virginia  Med.  and  Surg. 
Journal. 

One  of  the  best  works  on  the  subject  of  which  It 
treats  in  our  language. 

It  has  already  commended  itself  to  the  high  regard 
of  the  profession;  and  we  rnay  well  say  that  we 
know  of  no  single  volume  that  will  afford  the  source 
of  HO  thorough  a  drilling  In  the  principles  of  practice 
a«  this.  Students  and  pructilioners  should  make 
themselves  intimately  familiar  with  its  teachings — 
they  will  find  their  labor  and  study  most  amply 
repaid. — Cincinnall  Med,.  Observer. 

There  is  no  work  in  medical  literature  which  can 
fill  the  place  of  this  one.  It  is  the  Primer  of  the 
young  practitioner,  the  Koran  of  the  scieutillc  one. — 
SlelAwnci/pe. 


A  text-book  to  which  no  other  in  our  language  is 
comparable. — Charleston  Med.  Journal. 

The  lengthened  analysis  we  have  given  of  Dr,  Wil- 
liams's Principles  of  Medicine  will,  we  trust,  clearly 
prove  to  our  readers  his  perfect  competency  for  the 
task  he  has  undertaken — that  of  impaiting  to  the 
student,  as  well  as  to  the  more  experienced  practi- 
tioner, a  knowledge  of  those  general  principles  of 
pathology  on  which  alone  a  correct  practice  can  be 
founded.  The  absolute  necessity  of  such  a  work 
must  be  evident  to  all  who  protend  to  more  than 
mere  empiricism.  We  must  conclude  by  again  ex- 
pressing our  high  sense  of  the  immense  benefit  which 
Dr.  Williams  has  conferred  on  medicine  by  the  pub- 
lication of  this  work.  We  are  certain  that  in  the 
present  state  of  our  knowledge  his  Principles  of  Me<li- 
cine  could  not  possibly  be  surpassed.  While  we 
regret  the  loss  which  many  of  the  rising  generation 
of  practitioners  have  sustained  by  his  resignation  of 
the  Chair  at  University  College,  it  is  comforting  to 
feel  that  his  writings  must  long  continue  to  exert  a 
powerful  induonce  on  the  practice  of  that  profession 
for  the  improvement  of  which  he  bus  so  aHsiduously 
and  successfully  labored,  and  in  which  he  holds  so 
distinguished  a  position. — London  Jour,  of  Medicine. 


16 


Henry  C.  Lea's  Publications — {Practice  of  Medicine). 


-pLINT  [A  USTIN),  M.  D., 

-*-  Professor  of  the  Principles  and  Practice  of  ITedicine  in  Bellemie  llfsd.  College,  N.  T. 

A   TREATISE  _  ON    THE    PRINCIPLES    AND    PRACTICE    OF 

MEDICINE ;  designed  for  the  use  of  Students  and  Practitioners  of  Medicine.  In  one  large 
and  closely  printed  octavo  volume  of  867  pages;  handsome  extra  cloth,  $6  00;  or  strongly 
bound  in  leather,  with  raised  bands,  $7  00.      (Now  Ready.) 


A  book  of  inestimable  value,  as  the  recorded  expe- 
rieace  of  one  of  tlie  clearest  and  best  educated  minds 
ever  devoted  to  the  theory  and  practice  of  medicine. 
Dr.  Flint's  Theory  and  Practice  op  Medicine  will 
be  eagerly  perused  by  all  our  readers — will  be  re- 
garded as  the  Bible  of  praclical  medicine. — Buffalo 
Med.  and  Surg.  Journal,  May,  1866. 

In  following  out  such  a  plan  Dr.  Flint  has  suc- 
ceeded mo.st  admirably,  and  gives  to  his  readers  a 
work  that  is  not  only  very  readable,  interesting, 
and  concise,  but  in  every  respect  calculated  to  meet 
the  requirements  of  professional  men  of  every  class. 
The  student  has  presented  to  him,  in  the  plainest 
possible  mftnner,  the  symptoms  of  disease,  the  prin- 
ciples which  should  guide  him  in  its  treatment,  and 
the  difficulties  which  have  to  be  surmounted  in  order 
to  arrive  at  a  cori-ect  diagnosis.  The  practitioner, 
besides  having  such  aids,  has  otfered  to  him  the  con- 
clusion which  the  experience  of  the  professor  has 
enabled  him  to  arrive  at  in  reference  to  the  relative 
merits  of  different  therapeutical  agents,  and  difleient 
methods  of  treatment.  This  new  work,  as  a  whole, 
will  add  not  a  little  to  the  well-earned  reputation  of 
Prof.  Flint  as  a  medical  writer  and  teacher.  Tl:e 
number  of  years  in  which  he  has  been  engaged  in  the 
active  duties  of  his  profession,  both  in  public  and 
private  life,  have  given  him  an  amount  of  experi- 
ence which  has  eminently  fitted  him  for  the  produc- 
tion of  a  work  which  must  necessarily  extend  over 
such  a  wide  range  of  subjects.  We  cannot  see  how  it 
can  fail  to  meet  with  universal  favor. —  N.  Y.  Med. 
Record,  April  2,  1866. 

It  presents  a  brief,  but  concise  and  reliable  sum- 
mary of  those  pathological  and  therapeutical  views 
that  are  most  generally  accepted  by  the  profession  at 
the  present  time;  and  consequently  it  is  well  adapted 
for  a  text-book  in  Ihe  hands  of  students.  It  will  also 
form  a  valuable  addition  to  the  library  of  the  practi- 
tioner.— Hie  Chicago  Medical  Exarainer,  April,  1S66. 

The  Practice  of  Medicine  of  Prof.  Flint  is,  un- 
doubtedly, a  most  excellent  work,  and  is  much  better 
suited  to  the  special  needs  of  the  American  st\ident 
and  practitioner  than  any  other  accessible  to  them. 
We  predict  for  the  book  a  very  great,  and,  as  we  be- 
lieve, well  deserved  popularity. — Oincinnuti  Jour- 
nal of  Medicine,  March,  1866. 

Contains  all  that  has  recently  been  added  to  our 
knowledge  of  this  department  of  medicine. — Detroit 
Beview,  April,  1866. 

From  J.  Adams  Allen,  M.  D.,  LL.  D., 

Professor  of  Principles  and  Practice  of  3Iedieine, 

Rush  Medical  College,  Chicago. 
'  I  shall  take  great  pleasure  in  recommending  this 
work  as  a  text-book  iu  our  college,  and  also  for  the 
libraries  of  the  profession  generally.  It  is  a  timely 
and  absolutely  indispensable  contribution  to  the 
literature  of  the  profession. 


From  Walter  Carpenter,  M.  D., 
Professor  of  Theory  and .  Practice  of  Medicine, 

Vniv.  of  Vermont. 
I  consider  "  Flint's  Principles  and  Practice  of 
Medicine"  as  the  best  book  upon  the  subject,  that 
has  yet  come  under  my  notice,  for  many  other  rea- 
sons as  well  as  the  one  above  mentioned.  I  .shall 
most  surely  recommend  the  work  to  my  class,  and 
only  wish  every  member  had  a  copy. 

From  EicuARD  McSherrt,  M.  D., 
Prof,  of  Practice  of  Medicine,  Univ.  of  Maryland. 
I  am  much  pleased  with  this  work,  and  I  take 

pleasure  in   recommending  it  to  the  students  who 

attend  my  lectures. 

From  Israel  T.  Dana,  M.  D., 
Prof,  of  Theory  and  Practice  of  Medicine  in  Bowdoin 
College,  Brunswick,  ^le. 
On  examination  I  am  much  pleased  with  the  book, 
and  shall  warmly  recommend  it  to  our  college  stu- 
dent*, next  month,  when  my  lectures  at  Brunswick 
commence  again. 

From  E.  E.  Phelps,  M.  D., 
Prof,  of  Them'y  and  Practice  of  Medicine  in  Dart- 
mouth Med.  College,  N.  H. 
I  have  given  it  an  examination,  and  am  prepared 
to  recommend  it  to  my  clas.ses  as  a  text-book. 

From  J.  A.  Murphy,  M.  D., 
Prof,  of  Theory  and  .Practice  of  Medicine  in  Miami 
Med.  College,  Cincinnati,  Oliio. 
I  am  well  pleased  with  it,  and  shall  recommend  it 
to  the  class  of  Miami  Medical  College. 

From  A.  P.  Dutcher,  M.D., 

Prof,  of  Principles  and  Practice  of  Ifedicine  in 

Charity  Hasp.  Med.  Coll.,  Cleveland,  0. 

As  a  text-book  for  students  it  is  superior  to  ariy 

work  I  am  acquainted  with,  and  as  such  I  hope  it  will 

be  adopted  by  every  medical  college  in  the  land. 

From  Geo.  C.  Shattuck,  M.  D., 
Professor  of  Theory  and  Prn.ctice  of  Medicine, 

Mass.  Med.  College. 
I  have  recommended  the  book  to  the  students  and 
adopted  it  as  a  text-book. 

From  Thomas  F.  Eochester,  M.  D., 
Professor  of  Principles  and  Practice  of  Medicine, 

University  of  Buffalo. 

I  am   much  pleased  with   the  work;   during  the 

winter,  I  advised  the  class  to  use  it,  and  regret  that 

it  only  arrived  in  this  city  just  at  the  close  of  the 

term.     I  shall  employ  it  as  a  text-book. 


J^UNGLISON,  FORBES,  TWEEDIE,  AND  CONOLLT. 

THE  CYCLOPEDIA  OF   PRACTICAL  MEDICINE:    conaprising 

Treatises  on  the  Nature  and  Treatment  of  Diseases,  Materia  Medica  and  Therapeutics, 
Diseases  of  Women  and  Children,  Medical  Jurisprudence,  &c.  &c.     In  four  large  super-royal 
octavo  volumes,  of  3254  double-columned  pages,  strongly  and  handsomely  bound.     $15. 
*:^*  This  work  contains  no  less  than  four  hundred  and  eighteen  distinct  treatises,  contributed 
by  sixty-eight  distinguished  physicians. 


The  most  complete  work  on  practical  medicine 
extant,  or  at  least  in  our  language. — Buffalo  Medical 
and  Surgical  Joiirnal. 

For  reference,  it  is  above  all  price  to  every  practi- 
tioner.—  Western  Lancet. 
One  of  the  most  valuable  medical  publications  of 


the  day.     As  a  work  of  reference  it  is  invaluable. — 
Western  Journcd  of  Medicine  and  Surgery. 

It  has  been  to  us,  both  as  learner  and  teacher,  a 
work  for  ready  and  frec^uent  reference,  one  in  which 
modern  English  medicine  is  exhibited  in  the  most  ad- 
vantageous light. — 3Iedical  Examiner. 


nARLOW  {GEORGE  H.),  M.  D. 
A  MANUAL  OF  THE  PRACTICE  OF  MEDICINE.  With  Additions 

by  D.  F.  CoNDiE,  M.D.,  author  of  "A  Practical  Treatise  on  Diseases  of  Children,"  &e.    In 
one  handsome  octavo  volume  of  over  600  pages,  extra  cloth.     $2  50. 


Henry  C.  Lea's  Publtcations — (Practice  of  Medicine). 


17 


lyATSON  [THOMAS),  M.  D.,  ^c. 

LECTURES     ON    THE     PRINCIPLES    AND    PRACTICE    OF 

PHYSIC.     Delivered  at  King's  College,  London.     A  new  American,  from  the  last  revi.sed 
and  enlarged  English  edition,  with  Additions,  by  D.   Fkascis  Cuxdie,  M.  D.,  author  of 
"  A  Practical  Treatise  on  the  Diseases  of  Children,"  &c.     With  one  hundred  and  eighty- 
five  illustrations  on  wood.     In  one  very  large  and  handsome  volume,  imperial  octavo,  of 
over   1200  closely  printed  pages  in  small  type ;    extra   cloth,  $6  50  j  s'ti'ongly  bound   in 
leather,  with  raised  bands,  $7  50. 
Believing  this  to  be  a  work  which  should  lie  on  the  table  of  every  physician,  and  be  in  the  hands 
of  every  student,  every  effort  has  been  made  to  condense  the  vast  amount  of  matter  which  it  con- 
tains within  a  convenient  compass,  and  at  a  very  reasonable  price,  to  place  it  within  reach  of  all. 
In  its  present  enlarged  form,  the  work  contains  the  matter  of  at  least  three  ordinary  octavos, 
rendering  it  one  of  the  cheapest  works  now  offered  to  the  American  profession,  while  its  mechani- 
cal execution  makes  it  an  exceedingly  attractive  volume. 

the  student  in  the  acquirement  of  his  pi-ofession,  and 
no  less  worthy  of  frequent  consultation  and  reference 


Confessedly,  by  the  concnrreat  opinions  of  the 
Iiighest  critical  authorities  both  of  Groat  Britain  and 
this  country,  the  best  compend  of  the  principles  and 
practice  of  physic  that  has  yet  appeared. — Am.'Jour. 
of  the  Med.  Sciences. 

Commendation  of  these  lectures  would  be  only 
reiterating  the  often,  recorded  opinion  of  the  profes- 
sion. By  universal  consent  the  worlc  ranks  araona; 
the  very  best  text-books  in  our  language. — III.  and 
lad.  Med.  and  Sure/.  Journal. 

It  stands  now  confessedly  in  the  first  rank  of  the 
publications  relating  to  the  practice  of  medicine. — 
We.stern  .Journal  of  Med.  and  Surg. 

Dr.  Watson's  Lectures  may,  without  exaggeration, 
be  styled  a  inirror  of  the  practice  of  medicine. — Qin- 
cinnati  Lancet. 

We  cannot  speak  too  highly  of  this  truly  classical 
work  on  tlie  practice  of  medicine.  Take  it  all  in  all, 
it  is  the  very  best  of  books  of  its  kind;  equalled  by 
none  in  beauty  and  elegance  of  diction,  and  not  sur- 
jiassed  in  the  completeness  and  comprehensiveness 
of  its  contents.     It  will  be  an  indispensable  guide  to 


by  the  most  enlightened  practitioner.- 
Journal. 


-Chicago  Med. 


Dr  Watson's  Lectures  have  been  so  long  known 
and  celebrated  for  their  rare  combination  of  intrinsic 
excellence  and  attractive  style,  that  we  need  say  no 
more  of  this  edition  than  that  it  is  the  tie-st  woi'k  on 
the  subject  in  the  English  langua,ge,  for  the  .goueial 
purposes  boih  of  students  and  of  practitioners — all  of 
whom  we  advise  to  possess  themselves  of  a  copy,  if 
they  are  not  already  so  fortunate  as  to  have  one. — 
Bo.'ilon  Medical  and  Surgical  Journal. 

Young  men  will  find  in  the  work  before  us  the 
councils  of  wisdom,  and  the  old  men  the  woi'ds  of 
comfort.  Few  men  have  succeeded  so  well  as  Dr. 
Watson  in  throwing  together  science  and  common 
sense  in  the  treatment  of  disease. — Ohio  Mtd.  Journ. 

No  practitioner  should  be  without  the  new  edition. 
— N.  0.  Med.  News. 

This  work  is  now  truly  a  cyclopajdia  of  practical 
medicine. — New  York  Journal  of  Medicine. 


T^ICKSON  [SAMUEL  H.),  M.  D., 

Professor  of  Practice  of  Medicine  in  Jefferson  Medical  College,  Philadelphia. 

ELEMENTS  OF  MEDICINE  ;  a  Compendious  View  of  Pathology  and 

Therapeutics,  or  the  History  and  Treatment  of  Diseases.     Second  edition,  revised.     In  one 
large  and  handsome  octavo  volume,  of  750  pages,  extra  cloth.     $4  00. 

In  the  arrangement  and  classification  of  diseases  |  as  full  as  is  consistent  with  the  character  and  limits 
which  he  adopts,  in  his  description  and  treatment  of  '  of  the  work,  in  a  style,  for  interest   and    elegance. 


jjiiriicular  diseases,  he  is  worthy  of  all  commendation 
for  clearness  and  comprehensiveness,  and  in  other 
particulars  which  deeply  interest  and  strongly  im- 
press the  reader. — Peninsular  ■louriial  of  Medicine. 
This  part  we  consider  especially  excellent,  present- 
ing an  admirable  outline  of  the  principles  of  medicine, 


scarcely  second  to  that  which  has  made  the  work  of 
Dr.  Watson  so  popular. — Am.  Med.  Monthly. 

Prof.  DrcKSON's  work  supplies,  to  a  great  extent,  a 
desideratum  long  felt  in  American  medicine. — N.  0. 
Med.  and  Sarg.  Journal. 


J^ARCLAY  [A.  W.),  M.  D. 


A  MANUAL  OF  MEDICAL  DIAGNOSIS;  being  an  Analysis  of  the 

Signs  and  Symptoms  of  Disease.     Third  American  from  the  second  and  revisAl  London 
edition.     In  one  neat  octavo  volume  of  4'5I  pages,  extra  cloth.     i$3  60. 


A  work  of  immense  practical  utility. — London 
Med.  Times  and  Gazette. 

Calculated  to  be  of  great  advantage  not  only  to  the 
medical  student  but  to  the  professional  reader. — 
InMin  Quarterly  Journal. 

The  book  is  a  very  valuable  one  to  the  profession, 
and  we  most  heartily  commend  it  to  our  reader's. — 
Buffalo  Medical  and.  Surgical  Journal. 

To  the  junior  members  of  the  profession,  and  to 
stndent.s  we  could  scarcely  indicate  a  volume  present- 


ing greater  claims  to  their  attentive  consideration. — 
Brit.  Am.  3Ied.  Journal. 

The  book  should  be  in  the  hands  of  every  practical 
man. — Dublin  Med.  Press. 

There  are  but  few  practitioners  who  may  not  con- 
stxlt  its  pages  with  advantage,  and  who  will  not  find 
it  a  valuable  friend  when  Ihey  want  to  unravel  any 
complicated  case  of  disease. — Pacific  Med,  and  Surg. 
Journal. 

A  most  valuable  companion  to  the  practitioner  in 
private  practice. — Boston  Med.  and  Surg.  Journal. 


L 


OND ON  SO CIETY  OF  MEDICAL  OBSEll VA TION. 

WHAT  TO  OBSERVE  AT  THE  P>EDSIDE  AND  AFTER  DEATH 

IN  MEDICAL  CASES.  Published  under  the  authority  of  the  London  Society  for  Medical 
Ob.servation.  A  new  American,  from  the  second  and  revised  London  edition.  In  one  very 
handsome  volume,  royal  12mo.,  extra  cloth,     f  1  00. 


LAYCOCK'S  LECTURES  ON  THE  PRINCIPLED 
AND  Mkti(oi«  op  MnofCAi,  Obsruvation  ani>  Ku- 
ffKARCH.  For  the  ■o.pp,  of  advanced  Hludents  and 
jnni'>r  practitlonerH.  In  one  very  neat  royal  12mo. 
volume,  extra  dolii.    ifsl  00. 


HOLLAND'S'  MEDICAL  NOTES  AND  REFLEC- 
TIONS. From  the  thii'd  and  enlarged  English  edi- 
tion. In  one  handsome  octavo  volume  of  about 
.000  pages,  extra  cloth.    $.3  CO. 


18 


Henry  C.  Lea's  Publications — {Practice  of  Medicine). 


JpiLINT  {AUSTIN),  M.D., 

Professor  of  the  Principles  and  Practice  of  Medicine  in  Bellevwe  Hospital  Med.  College,  N.  T. 

PHYSICAL  EXPLORATION  AND   DIAGNOSIS  OF   DISEASES 

AFFECTING   THE   RESPIRATORY   ORGANS.     Second  and  revised  edition.     In  one 

handsome  octavo  volume.  {Nearly  ready.) 
During  the  ten  years  which  have  elapsed  since  the  preparation  of  the  first  edition  of  this  work, 
much  has  been  added  to  our  knowledge  of  its  subject.  The  position  of  the  author  has  been  such 
as  to  keep  him  necessarily  familiar  with  every  step  of  progress,  and  to  enable  him  to  test  the  im- 
portance of  all  investigations.  He  has  revised  the  work  thoroughly,  and  it  may  therefore  be 
regarded  as  entirely  on  a  level  with  the  most  advanced  condition  of  its  important  topic. 


J^Y  THE  SAME  A  UTHOR.  ■       

A  PPvACTICAL  TREATISE  ON  THE  DIAGNOSIS,  PATHOLOGY, 

AND  TREATMENT  OF  DISEASES  OF  THE  HEART.     In  one  neat  octavo  volume  of 

nearly  500  pages,  with  a  plate;  extra  cloth,  $3  50. 
We  question  the  fact  of  any  recent  American  author 
in  our  profeS'<ioQ  being  more  extensively  kuown,  or 
more  deservedly  esteemed  in  this  country  than  Dr. 


Flint.  We  willingly  acknowledge  his  success,  more 
particularly  in  tne  volume  on  diseases  of  the  heart,  in 
makingan  extended  personal  clinical  study  available 
for  purposes  of  illustration,  in  connection  with  cases 
which  have  been  reported  by  other  trustworthy  ob- 


servers. The  work  of  Dr  Flint,  which  has  received 
this  Short  notice  at  our  hands,  in  connection  with  his 
other  volume,  whose  title  we  have  placed  at  the  head 
of  our  observations,  may  be  regarded  as  constituting 
a  complete  guide  to  the  diagnosis  of  diseases  of  the 
chest;  and  for  this  purpose  we  have  much  pleasure 
and  every  confidence  in  recommending  them. — Brit. 
and  For.  Med.-Ghir.  Review. 


BLAKISTOJf    ON    CERTAIN    DISEASES    OF    THE 
CHEST.     In  one  volume  octavo.     .$1  2-5. 
BUCKLER   ON   FIBRO-BRONCHITIS  AND  RHEU- 
MATIC PNEUMONIA.     In  one  octavo  vol.,  extra 
cloth,  pp.  1.50.     SI  2.5. 

FISKE  FUND  PRIZE  ESSAYS.— LEE  ON  THE  EF- 
FECTS OF  CLIMATE  ON  TUBERCULOUS  DI.S- 
E.^SE.  AND  WAKKEN  ON  THE  INFLUENCE  OF 
PREGNANCY  ON  THE  DEVELOPMENT  OF  TO- 
BEKCLES.  Together  in  one  neat  octavo  volume, 
extra  cloth,     %\  00. 

HUGHES'   CLINICAL   INTRODUCTION  TO  AUS- 


CULTATION AND  OTHER  MODES  OF  PHYSICAL 
DIAGNOSIS.  Second  edition.  One  volume  royal 
12mo.,  extra  cloth,  pp.  304      $1  2.5. 

WALSHE'S  PRACTICAL  TREATISE  ON  DISEASES 
OF  THE  LUNGS.  Third  American,  from  the  third 
revised  and  much  enlarged  London  edition.  In  one 
neat  octavo  volume  of  nearly  500  pages,  extra  cloth. 
Price  $3  00. 

WALSHE^S  PRACTICAL  TRE.\TISE  ON  THE  DIS- 
EASES OF  THE  HEART  AND  GREAT  VESSELS. 
Third  American,  from  the  third  revised  and  much 
enlarged  London  edition.  In  one  handsome  oclavo 
volume  of  420  pages,  extra  cloth.    $3  00. 


8 


MITH  [EDWARD),  M.D. 

CONSUMPTION;  ITS  EARLY  AND  REMEDIABLE  STAGES.    In 

one  neat  octavo  volume  of  254  pages,  extra  cloth.     $2  25. 


8 


ALTER  [K  H.),  M.D. 

ASTHMA ;  its  Pathology,  Causes,  Consequences,  and  Treatment. 

one  volume,  octavo,  extra  cloth.     $2  50. 


In 


8 


.D. 


LADE  [D.  D. 

DIPHTHERIA;  its  Nature  and  Treatment,  with  an  account  of  the  His- 
tory of  its  Prevalence  in  various  Countries.  Second  and  revised  edition.  In  one  neat 
royal  12mo.  volume,  extra  cloth.     $1  25.     {Just  isstied.) 


^RINTON  [WILLIAM),  31. D.,  F.R.S. 


LECTURES  ON  THE  DISEASES  OE  THE  STOMACH;  with  an 

Introduction  on  its  Anatomy  and  Physiology.  From  the  second  and  enlarged  London  edi- 
tion. With  illustrations  on  wood.  In  one  handsome  octavo  volume  of  about  300  pages, 
extra  cloth.     $3  25.      {.Tust  issjied.) 


ITowhere  can  be  found  a  more  full,  accurate  plain, 
and  instructive  history  of  these  diseases,  or  more  ra- 
tional views  respecting  their  pathology  and  therapeu- 
tics.—,4'/)i.  Jonrn.  of  the  Med-  Sciences,  April,  1S6.5. 

The  first  edition  of  this  work  became,  immediately 
after  its  publication,  a  standard  authority  on  the  dis- 
eases, functional  and  organic,  of  the  primal  organ  of 
the  human  machine.  It  is  unnecessary  here  to  repeat 
the  praise  which  we  formerly  bestowed  on  the  book 


The  most  comi)lete  work  in  our  language  upon  the 
diagnosis  and  treaiment  of  these  puzzlin.§  and  impor- 
tant diseases. — Boston  Med.  and  Surg.  Journal,  Nov. 
186.5. 

These  lectures  comprise  a  brief  but  condensed  and 
quite  perfect  account  of  what  is  at  present  known 
concerning  diseases  of  the  stomach.  Th.e  anatomy, 
physiology,  symptoms,  and  treatment  are  so  pre- 
sented as  to  make  the  work  a  very  instructive  and 


when  it  was  a  debutant,  soliciting  professional  favor.  |  popular  one  with  practitioners  of  medicine. — Buffalo 
— BT~it.  and  For.  Med.-Ghir.  Review,  April,  1865.  I  Med.  and  Surg.  Journal,  Dec.  1865 


H 


ABERSHON  (S.  0.),  M.D. 


PATHOLOGICAL  AND  PRACTICAL  OBSERYATIONS  ON  DIS- 
EASES OF  THE  ALIMENTARY  CANAL,  (ESOPHAGUS,  STOMACH,  CiEClTM,  AND 
INTESTINES.  With  illustrations  on  wood.  In  one  handsome  octavo  volume  of  312 
pages,  extra  cloth.     $2  50. 


Henry  C.  LexV's  PunLiCATiONS — {Practice  of  Medicine). 


19 


pUMSTEAD  {FREEMAN  J.),  31.  D., 

J-^        Leatti^rer  on  Mriteria  Medica  and  Venereal  Diseaws  at  the  Ool.  of  Phys.  and  Hurg..  Neio  York.  A-c. 

THE  PATHOLOGY  AND  TREATMENT  OF  VENEREAL  DIS- 

EASES.     Including?  the  results  of  recent  investigations  upon  the  subject.     A  new  and  re- 
vised edition,  with  illu.strations.     In  one  large  and  handsome  octavo  volume  of  640  pages, 
extra  cloth,  $5  00.     {Lately  Issued.) 
During  the  short  time  which  has  elapsed  since  the  appearance  of  this  work,  it  has  assumed  the 
position  of  a  recognized  authority  on  the  subject  wherever  the  language  is  spoken,  and  its  transla- 
tion into  Italian  shows  that  its  reputation  is  not  confined  to  our  own  tongue.     The  singular  clear- 
ness with  which  the  modern  doctrines  of  venereal  diseases  are  set  forth  renders  it  admirably 
adapted  to  the  student,  while  the  fulness  of  its  practical  details  and  directions  as  to  treatment 
makes  it  indispensable  to  the  practitioner.     The  few  notices  subjoined  will  show  the  verj'  high 
position  universally  accorded  to  it  by  the  medical  press  of  both  hemispheres. 

Well  known  as  one  of  the  >)est  authorities  of  the  !  our  approval  and  praise  as  the  second  edition  of  Dr. 


jivesent  day  on  the  subject. — British  and  Fur.  Mtd.- 
Chirurg.  Review,  April,  1S66. 

A  regular  store-house   of   special  Information. — 
London  Lancet,  Feb.  24,  1866. 

A  remarkably  clear  and  full  systematic  treatise  on 
the  whole  subject. — Land.  Med,.  Time.s  and  Gazette. 

The  best,   completest,  fullest  monograph   on  this  i  have  iu  his  possession    and,  we  may  further  say,  tti« 

ibiectin  ourlanguage.-Br«i.s7i^mericfm.7oMr««Z.  '  onlyhoo}^  upon  the  subject  which  he  should  acknow- 
'^     °  ledge  as  compeient  authority. — Buffalo  Medical  ana 


Bumstead's  work. —  Glangow Med,.  JoxtrnaJl,  Oct.  1S64. 

"We  know  of  no  treatise  in  any  language  which  is 
its  equal  in  point  of  completeness  and  practical  sim- 
plicity.—  Boston  Medical  and  Surgical  Jowrnal, 
Jan.  30,  1861. 

The  hook  is  one  which  every  practitioner  should 


subject  in  our  language 

IndAspensahle  in  a  medical  library. — Pacific  Med. 
ayid  Sarg.  Journal. 

We  Iftive  no  doubt  that  it  will  supersede  in  America 
every  other  treatise  oa  Venereal. — San  Francisco 
Mid.  Press,  Oct.  1864. 

A  perfect  compilation  of  all  that  i.s  worth  knowing 
oa  venereal  diseases  in  general.  It  tills  up  a  gap 
which  has  long  been  felt  in  English  medical  literature. 
— Brit,  and  Foreign  Med.-Ohirurg.  Review,  Jan.,  'e.'J. 

We  have  not  met  with  any  which  so  highly  merits 


Surgical  Journal,  July,  1864. 

The  best  work  with  which  we  are  acquainted,  and 
the  most  convenient  hand-book  for  the  busy  practi- 
tioner — Oincinnali  Lancet,  July,  1864. 

The  author  has  spared  no  labor  to  make  this  edition 
worthy  of  the  reputation  acquired  by  the  last,  and  we 
believe  that  no  iinpiovemeut  or  suggestion  worthy  of 
notice,  recorded  since  the  last  edition  was  published, 
has  been  left  unnoticed. — Dublin  Quarterly  -Journal 
of  Medical  Science,  August,  1864. 


'OICORD  {P.),  M.D. 

LETTERS  ON  SYPHILIS.     Translated  by  W.  P.  Lattimore,  M.D. 

In  one  neat  octavo  volume,  of  270  pages,  extra  cloth,  $2  00. 


TALLEMAND  AND   WILSON. 
A   PRACTICAL  TREATISE    ON    THE    CAUSES,    SYMPTOMS, 

AND   TREATMENT   OF    SPERMATORRH(EA.     By  M.  Lallemand.     Translated  and 

edited  by  Henry  .J.  McDougall.     Fifth  American  edition.     To  which  is  added ON 

DISEASES  OF  THE  VESICULJa  SEMINALES,  axd  their  associated  oe&ans.  With 
special  reference  to  the  Morbid  Secretions  of  the  Prostatic  and  Urethral  Mucous  Membrane. 
By  Marris  Wilson,  M.D.    In  one  neat  octavo  volume,  of  about  400  pp.,  extra  cloth,  $2  75. 


nUBD  (GEORGE),  M.D. 

ON  DISEASES  OF  THE  LIVER.     Third  American,  from  the  third 

and  enlarged  London  edition.    In  one  very  handsome  octavo  volume,  extra  cloth,  with  four 
beautifully  colored  plates,  and  numerous  wood-cuts.     pp.  600.     $4  00. 


TA  ROCHE  [R.),  M.D. 


B 


YELLOW  FEVER,  considered  in  its  Historical,  Pathological,  Etio- 
logical, and  Therapeutical  Pi-elations.  Including  a  Sketch  of  the  Disease  as  it  has  occurred 
in  Philadelphia  from  1699  to  1854,  with  an  examination  of  the  connections  between  it  and 
the  fevers  known  under  the  same  name  in  other  parts  of  tempjerate  as  well  as  in  tropical 
regions.  In  two  large  and  handsome  octavo  volumes,  of  nearly  1500  pages,  extra  cloth,  $7  00. 

Y  THE  SAME  AUTHOR.  

PNEUMONIA ;  its  Supposed  Connection,  Pathological,  and  Etiological, 

with  Autumnal   Fevers,  including  an  Inquiry  into  the  Existence  and  Morbid  Agency  of 
Malaria.     In  one  handsome  octavo  volume,  extra  cloth,  of  500  pages.     $3  00. 


TYONS  (ROBERT  D.),  K.  G.  0. 
A  TREATISE  ON  FEVER;  or.  Selections  from  a  Cour.se  of  Lectures 

on  Fever.    Being  piart  of  a  Course  of  Theory  and  Pr.ictice  of  Medicine.    In  one  neat  octavo 
volume,  of  362  pages,  extra  cloth.     §2  25. 


BARTLETT  on  THE  HISTORY,  DIAGXOSLS,  AND 

TkkAT.MKST  OK  TirK   FF-VKRH  OF  THK    U.VITBIJ    STATKS. 

a  new  and  revised  edition.  By  Alo.nzoCj.akk,  .M  IJ., 
Prof,  of  Pathologv-  and  Practical  Medicine  in  the 
N.  y.  College  of  Phyj-icians  and  Surgeons,  &c.  In 
one  octavo  volume,  of  GOO  pageH,  extra  cloth,  ijil  2.J. 


Cr.YMER  ON  FEVERS;    THEIR   DIAGNOSIS,  PA- 

Tifojyooy  AND  TnKAT.WRNT.     In  one  octavo  voluirve 

of  600  pagi^H.  leather      $1   ir>. 
TODDS  CLINICAL  LECTURES  ON  CERTAIN  ACUTE 

DisKAsKs.   In  ont!  ni;at  octavo  volume,  of  ;JilO  page.s, 

extra  cloth.    f^J,  00. 


20 


Henky  G.  Lea's  Publications — {Practice  of  Medicine) 


JOOBEETS  (  WILLIAM),  WL  D.. 

-*-  *^  Lecturer  on  Medicine  in  the  Manchester  School  of  Medicine,  &o. 

A  PRACTICAL  TREATISE   OlsT  URINARY  AND   RENAL   DIS- 

EASES,  including  Urinary  Deposits. '  Illustrated  by  numerous  cases  and  engravino-s.  In 
one  very  handsome  octavo  volume  of  516  pp.,  extra  cloth.  $4  50.  (Now  Ready.) 
The  want  has  for  some  time  been  felt  of  a  Work  which  should  render  accessible  to  the  American 
profession  in  a  compendious  and  convenient  form,  the  results  of  the  numerous  and  important 
researches  which  have  of  late  years  elucidated  the  pathology  of  Urinary  and  Renal  Diseases.  It 
has  been  the  aim  of  the  author  in  the  present  volume  to  set  forth  in  a  form  divested  of  undue 
technicality,  the  practical  condition  of  the  subject  in  its  most  advanced  stage  of  progress.  In 
endeavoring  to  accomplish  this,  he  has  refrained  from  crowding  the  volume  with  minute  chemical 
and  physiological  details,  which  would  unfit  it  for  its  object  of  affording  to  the  physician  a  guide 
in  his  daily  practice,  and  to  the  student  a  condensed  and  intelligible  compendium  of  ali  that  is 
practically  important  on  the  subject.  To  aid  in  this,  numerous  cases  and  illustrations  have  been 
introduced  throughout  the  work. 


In  carrying  out  this  design,  he  has  not  only  made 
good  use  of  his  own  practical  knowledge,  but  has 
brought  together  from  various  sources  a  vast  amount 
of  information,  some  of  which  is  not  generally  pos- 
sessed by  the  profession  in  this  country.  We' must 
now  bring  our  notice  of  this  book  to  a  close,  re 
gretting  only  that  we  are  obliged  to  resist  the  temp- 
tation of  giving  further  extracts  from  it.  Dr.  Roberts 
has  already  on  several  occasions  placed  before  the 
profession  the  results  of  researches  made  by  him  on 
various  points  connected  with  the  urine,  and'had  thus 
led  us  to  expect  from  him  something  good — in  whicli 
expectation  we  ha^e  been  by  no  means  disappointed. 


sive  worlc  on  urinary  and  i-enal  diseases,  considered 
in  their  strictly  practical  aspect,  that  we  possess  iu 
the  English  language. — British  Medical  Journal, 
Dec.  9,  lSti.5. 

We  have  read  this  hook  with  much  satisfaction. 
It  will  take  its  place  beside  the  best  treatises  in  our 
language  upon  urinary  pathology  and  therapeutics. 
Not  the  least  of  its  merits  is  that  the  author,  unlike 
some  other  book-makers,  is  contented  to  withhold 
much  that  he  is  well  qualified  to  discuss  in  order  to 
impart  to  his  volume  such  a  strictly  practical  charac- 
ter as  cannot  fail  to  render  it  popular  among  British 
readers. — London  Med.  Times  and  Gazette,  Miirch 
17,  18(il>. 


The  book  is,  beyond  question,  the  most  comprehen 

^*^  "  Bird  on  Urinary  Deposits,"  being  for  the  present  out  of  print,  gentlemen  will  find  in  the 
ibove  work  a  trustworthy  substitute. 


MOELAND  ON  THE  MORBID  EFFECTS  OF  THE 
RETENTION  IN  THE  BLOOD  OF  THE  ELE- 
MENTS OP  THE  URINARY  SECRETION.  In  one 
small  octavo  volume,  83  pages,  extra  cloth.  75 
cents. 

BLOOD  AND   URINE  (MANUALS  ON).     By   J.  W. 


Grippth,  G.  0.  Reese,  and  A.  Markwtck.  One 
volume,  royal  12mo.,  extra  cloth,  with  plates,  pp. 
460.  fil  2.5. 
FRICK  ON  RENAL  AFFECTIONS  ;  their  Diagnosis 
and  Pathology.  With  illustrations.  One  volume, 
royal  12mo.,  extra  cloth.     75  cents. 


jyjJGKNILL  {J.  C.),M.D., 

-'-•'  Med.  Superintendent  of  the  Devon 


and 

■  Lunatic  Asylum, 


DANIEL  H.  TDKE,M.n., 

-*-^  Visiting  Medical  Officer  to  the  York 


Retreat. 


A  MANUAL  OF    PSYCHOLOGICAL    MEDICINE;  containing  tlie 

History,  Nosology,  Description,  Statistics,  Diagnosis,  Pathology,  and  Treatment  of  In- 
sanity.    With  a  Plate.     In  one  handsome  octavo  volume,  of  536  pages,  extra  cloth.     $4  25. 

A  work  alike  characterized  by  great  classical  ele- 
gance and  a  careful  and  judicious  discrimination  on 
the  diagnosis,  pathology  and  treatment  of  this  dread- 


ful malady. —  Va.  Med.  and  Surg.  Jouriud. 

We  do  not  know  where  anything  can  be  found  in 
the  literature  of  the  specialty  to  compare  with  these 


essays,  in  complete  and  logical  treatment,  and  the 
clear,  practical  manner  in  which  their  subjects  are 
discussed.  They  will  be  cited  as  authority  wherever 
the  language  is  used,  and  will,  no  doubt,  be.  exten- 
sively translated. — Anier.  Journal  of  Insanity. 


HARRISON'S  ESSAY  TOWARDS  A  CORRECT 
THEORY  OF  THE  NERVOUS  SYSTEM.  In  one 
octavo  volume  of  292  pp.     $1  50. 

SOLLY   ON   THE  HUMAN   BRAIN;    its  Structure, 


Physiology,  and  Diseases.  From  the  Second  and 
much  enlarged  London  edition.  In  one  octavo 
volume  of  .500  pages,  with  120  wood-cuts;  extra 
cloth.     -$2  50. 


TONES  {G.  HANDFIELD),  M.  D., 

"  Physician  to  St.  Mary's  Hospital,  &g. 

CLINICAL  OBSERVATIONS  ON  FUNCTIONAL  NERYOUS 

DISORDERS.  Publishing  in  the  "Medical  News  and  Library,"  for  1865  and  1866. 
To  form  one  handsovie  octavo  volume  of  about  four  hundred  'pages. 

This  work,  which  is  now  passing  through  the  "Library  Dep.artment"  of  the  Medical  News 
AND  LiBRARr,  will  be  completed  during  the  present  year,  and  will  be  issued  separate  in  a  handsome 
volume  in  December.  The  author  is  known  as  a  physician  of  large  experience  and  scientific  re- 
search, and  his  ample  opportunities  of  investigating  the  symptoms  and  treatment  of  this  obscure 
and  intractable  class  of  diseases  have  been  turned  to  good  account.  Few  disorders  occur  more  fre- 
quently in  practice  or  prove  more  embarrassing  than  these,  and  the  profession  has  long  felt  the 
want  of  an  authoritative  practical  treatise  devoted  especially  to  them.  The  subjects  discussed  by 
the  author  are  :  General  Pathology — Cerebral  Anaemia — Ansemia  of  the  Spinal  Cord — Hypersomia 
of  the  Brain — Spinal  Hypersemia — Cerebral  Paresis  (or  Paralysis) — Spinal  Paresis — Cerebral  Ex- 
citement—  Delirium  Tremens  —  Tetanus  —  Catalepsy — Epilepsy — Headache — Vertigo — Chorea — 
Paralysis  Agitans — Spasmodic  Afiections — Sleeplessness — Facial  Neuralgia — Facial  Paralysis — 
Retinal  Hyperajsthesia — Throat  DyssB,sthesia — Lingual  Neuralgia — Brachial  Neuralgia — Sciatica — 
Angina  Pectoris — Respiratory  Neuroses— Myalgia — Abdominal  Neuralgia — Neuroses  of  Urinary 
Organs  and  Intestines — Uterine  Neuroses — Cutaneous  Neuroses — Mal.Trioid  Disorder — Secretion 
Fluxes — Hysteria — Syphilitic  and  Rheumatic  Nerve  Affections — Remedies. 

The  wide  scope  of  the  treatise,  and  its  practical  character,  as  illustrated  by  the  large  number 
of  cases  reported  in  detail  by  the  author,  can  hardly  fail  to  render  it  exceedingly  valuable  to 
the  profession.  For  terms  of  the  "American  Journal  of  the  Medical  Sciences"  and  the  "Medical 
News,"  see  p   1. 


Henry  C.  Lea's  Publications — {Diseases  of  the,  Skin). 


21 


lYILSON  ( ERASM  US ) ,  F.  R.  S., 

0]St  DISEASES  OF  THE  SKIX.     The  sixth  American,  from  the  fifth 

and  enlarged  English  edition.     In  one  large  octavo  volume  of  nearly  700  pages,  extra 
cloth.      $4  60.     Also—  ' 

A  SERIES   OF   PLATES   ILLUSTRATING  "WILSON    ON   HIS- 

EASES  OF  THE  SKIN;"  consisting  of  twenty  beautifully  executed  plates,  of  which  thir- 
teen are  exquisitely  colored,  presenting  the  Normal  Anatomy  and  Pathology  of  the  Skin, 
and  embracing  accurate  representations  of  about  one  hundred  varieties  of  disease,  most  of 
them  the  size  of  nature.     Price,  in  extra  cloth,  $5  80. 
Also,  the  Text  and  Plates,  bound  in  one  handsome  volume,  extra  cloth.     Price  $9  50. 
This  classical  work  has  for  twenty  years  occupied  the  position  of  the  leading  authority  on  cuta- 
neous disenses  in  the  English  language,  and  the  industry  of  the  author  keeps  it  on  a  level  with  the 
advance  of  science,  in  the  frequent  revisions  which  it  receives  at  his  hands.     The  Lirge  size  of  the 
volume  enables  him  to  enter  thoroughly  into  detail  on  all  the  subjects  embraced  in  it,  while  its 
very  moderate  price  places  it  within  the  reach  of  every  one  interested  in  this  department  of  practice. 


Sucli  a  work  as  the  one  before  us  is  a  most  capital 
and  acceptable  help.  Mr.  Wilson  has  long  been  held 
as  high  authority  in  this  department  of  medicine,  and 
his  book  on  diseases  of  the  skin  has  long  been  re- 
garded as  one  of  the  best  text-boolcs  extant  on  the 
subject.  The  present  edition  is  carefully  prepai-ed, 
and  brought  up  in  its  revision  to  the  present  time.  In 
this  edition  we  have  also  included  the  beautifnl  series 
of  plates  illustrative  of  the  text,  and  in  the  last  edi- 
tion published  separately.  There  are  twenty  of  these 
plate.-^,  nearly  all  of  them  colored  to  nature,  and  ex- 
hibiting with  great  fidelity  the  various  groups  of 
diseases  treated  of  iu  the  body  of  the  work. — Oin- 
cinnati  Lancet,  June,  1SU3. 

No  one  treating  skin  diseases  should  be  without 
a  copy  of  this  standard  work.  —  Canada  Lancet. 
Augus't,  1S63. 

}Y  THE  SAME  AUTHOR.  — 


We  can  safely  recommend  it  to  the  profession  as 
the  best  work  on  the  subject  now  in  existence  in 
the  English  language. — Medical  Times  and  Gazette. 

Mr.  Wilson's  volume  is  an  excellent  digest  of  tlie 
actual  amount  of  knowledge  of  cutaneous  diseases  ; 
it  includes  almost  every  fact  or  opinion  of  importance 
connected  with  the  anatomy  and  pathology  of  the 
skin. — British  and  Foreign  Medical  Review. 

These  plates  are  very  accui'afe,  and  are  executed 
with  an  elegance  and  taste  which  are  highly  creditable 
to  the  artistic  skill  of  the  American  artist  who  executed 
them. — St.  Lnuis  Med.  Journal. 

The  drawings  are  very  perfect,  and  the  fiui.sh  and 
coloring  artistic  and  correct;  the  volume  is  au  indis- 
pensable companion  to  the  book  it  illustrates  and 
completes. — Charleston  Medical  Journal. 


B' 


THE  STUDENT'S  BOOK  OF  CUTANEOUS  MEDICINE  and  Dis- 

EASES  OP  THE  SKIN.     In  one  very  handsome  royal  12mo.  volume.     $.3  50.     (Now  Ready.) 
This  new  class-book  will  be  admirably  adapted  to  I      Thoroughly  practical  in  the  best  sense. — Brit.  Med. 


the  necessities  of  students. — Lancet. 


Journal. 


-DY  THE  SAME  AUTHOR.  

HEALTHY   SKIN;   a  Popular  Treatise  on  the  Skin  and  Hair,  their 

Preservation  ajd  Management.     One  vol.  I2mo.,  pp.  291,  with  illustrations,  cloth.     $1  00. 


'KTELIGAN  {J.MOORE),  M.D.,M.R.I.A., 
A    PRACTICAL    TREATISE    ON    DISEASES    OF    THE    SKIN. 

Fourth  American  edition.     In  one  neat  royal  12mo.  volume,  extra  cloth.     $1  50. 
JjY  THE  SAME  AUTHOR.  

ATLAS   OF   CUTANEOUS    DISEASES.      In   one  beautiful   quarto 

volume,  with  exquisitely  colored  plates,  &c.,  presenting  about  one  hundred  varieties  of 

di.sease.     Extra  cloth,  $5  50. 

of  the  pathology  and  treatment  of  eruptive  diseases. 
It  possesses  the  merit  of  .giving  short  and  condensed 
descriptions,  avoiding  the  tedious  minuteness  of 
many  writers,  while  at  the  same  time  the  work,  as 
its  title  implies,  is  strictly  practical. — Glasgow  Med. 
Journal. 

A  compend  which  will  very  much  aid  the  practi- 
tioner in  this  difficult  branch  of  diagnosis.  Taken 
with  the  beautiful  plates  of  the  Atlas,  which  are  re- 
markable for  their  accuracy  and  beauty  of  coloring, 
it  constitutes  a  very  valuable  addition  to  the  library 
of  a  practical  man. — Buffalo  Med.  Journal. 


The  diagnosis  of  eruptive  disease,  however,  under 
all  circumstances,  is  very  difficult.  Nevertheless, 
Dr.  Jfeligaa  has  certainly,  "as  far  as  possible,"  given 
a  faitliful  and  accurate  representation  of  this  class  of 
disease.s,  and  there  can  be  no  doubt  that  these  plates 
will  be  of  great  use  to  the  student  and  practitioner  in 
drawing  a  diagnosis  as  to  the  class,  order,  and  species 
to  which  the  particular  case  may  belong.  While 
looking  over  the  "Atlas"  we  have  been  induced  to 
examine  also  the  "Practical  Treatise,"  and  we  are 
inclined  to  consider  it  a  very  superior  work,  com- 
bining accurate  verbal  description  with  sound  views 


TJILLIER  {THOMAS),  M.D., 

Physician  to  the  Skin  Department  of  University  College  Hospital,  &o. 

HAND-ROOK  OF  SKIN  DISEASES,  for  Students  and  Practitioners. 

In  one  neat  royal  12mo.  volume  of  about  300  pages,  with  two  plates ;  extra  cloth,  $2  25. 

{Just  Lisued.) 

A  text-book  well  adapted  to  the  student,  and  the 
information  contained  iu  it  show.s  the  author  to  be 
au  nvmaii,  with  tlio  scientific  medicine  of  the  day. — 
London  Lancet,  Feb.  23,  ISM. 

In  the  3.")0  pages,  the  practitioner  will  find  scattered 
a  great  deal  of  very  valuable  information  not  to  be 
rnet  With  in  more  pretentious  and  i'Xlonsive  works  — 
Med.  and  S'lrg.  Review  {Auntralasian),  Oct.  1,  1SC5. 


Tlie  work  of  Dr.  Hillier  will  unquestionably  serve 
the  student  as  a  useful  and  faithful  guide  to  the  ac- 
quirement of  a  knowledge  of  fkln  diHoases.  The 
treatment  laid  down  by  the  author  in  Himple,  rational, 
and  in  accordance  with  the  re.nnlts  of  an  extended 
experience.  Dr.  H.  avoids  all  unneceBsary  multipli- 
cation of  remedieM,  and  rejcctH  all  of  doubtful  value. 
—Am.  Jimrnal  Med.  hoiencea,  July,  18tJ;3. 


22 


Henry  C.  Lea's  Publications — (Dii^eases  of  Children). 


WE^r  {CHARLES),  31.  D., 

Physician  to  ihe  Ho-rpital  for  Sick  Childrera,  S:c. 

LECTURES   ON   THE   DISEASES    OF   IXFAKCY  AND   CHILD- 

HOOD.  Fourth  American  from  the  fifth  re.ised  and  enlarged  English  edition.  In  one 
large  and  handsome  octavo  volume  of  666  closely-printed  pages.  Extra  cloth,  $4  60 ; 
leather,  $5  60.      {Just  issued.) 

This  work  may  now  fairly  claim  the  position  of  a  standard  authority  and  medical  classic.  Five 
editions  in  England,  four  in  America,  four  in  Germany,  and  translations  in  French,  Danish, 
Dutch,  and  Russian,  show  how  fully  it  has  met  the  wants  of  the  profession  by  the  soundness  of  its 
views  and  the  clearness  with  which  they  are  presented.  Few  practitioners,  indeed,  have  had  the 
opportunities  of  observation  and  experience  enjoyed  by  the  Author.  In  his  Preface  he  remarks, 
"The  present  edition  embodies  the  results  of  1200  recorded  cases  and  of  nearly  400  post-mortem 
examinations,  collected  from  between  30,000  and  40,000  children,  who,  during  the  past  twenty- 
six  years,  have  come  under  my  care,  either  in  public  or  in  private  practice."  The  universal  favor 
with  which  the  work  has  been  received  shows  that  the  author  has  made  good  use  of  these  unusual 
advantages. 

infancy  and  childhood. — Culwnihus  Review  of  Med. 
and  Surgery. 

To  occupy  in  medical  literature,  in  regard  to  dis- 
eases of  children  the  enviable  position  which  Dr. 
Watson's  treatise  does  ou  the  diseases  of  adult.s  is 
now  very  generally  assigned  to  our  author,  and  his 
book  is  in  the  hands  of  the  profession  everywliere  as 
aa  original  work  of  great  value. — Md.  and  Va.  Med. 
and  Su.rff.  -/oitrnal. 

Dr.  West's  works  need  no  recommendation  at  this 
date  from  any  hands.  The  volume  before  us,  espe- 
cially, has  won  for  itself  a  large  and  well-deserved 
popularity  among  the  profession,  wherever  the  Eng- 
lish tongue  is  spoken.  .Many  years  will  elapse  before 
it  will  be  repUxced  in  public  estimation  by  any  similar 
treatise,  and  seldom  again  will  the  same  subject  be 
discussed  in  a  clearer,  more  vigorous,  or  pleasing 
style,  with  equal  simplicity  and  power. — Oharleston 
Med.  .Jmi/r.  and  Review. 

There  is  no  part  of  the  volume,  no  subject  on  which 
it  treats  which  does  not  exhibit  the  keen  perception, 
the  clear  judgment,  and  the  sound  reasoning  of  tli-e 
author.  It  will  be  found  a  most  useful  guide  to  the 
young  practitioner,  directing  him  in  his  management 
of  children's  diseases  in  the  clearest  possible  manner, 
and  enlightening  him  on  many  a  dubious  pathological 
point,  while  the  older  one  will  find  in  it  many  a  sug- 
gestion and  practical  hint  of  great  value. — Brit.  Am. 
Med  Journal. 


Of  all  the  English  writers  on  the  diseases  of  chil-  1 
dren,  there  is  no  one  so  entirely  satisfactoiy  to  us  as 
Dr.  West.     For  years  we  have  held  his  opinion  as  j 
judicial,  and  have  regarded  him  as  one  of  the  highest  ! 
living  authorities  in  the  difficult  department  of  medi-  ] 
cal  science  in  which  he  is  most  widely  known.     His 
writings  are  characterized  by  a  sound,  practical  com-  ! 
mon  sense,  at  the  same  time  that  they  bear  the  marks  1 
of  the  most  laborious  study  and  investigation.     We 
commend  it  to  all  as  a  most  reliable  adviser  on  many  j 
occasions  when  many  treatises  on  the  same  subjects 
,will  utterly  fail  to  help  us.    It  is  supplied  with  a  very 
copious  general  index,  and  a  special  index  to  the  for- 
mulfe  .scattered  throughout  the  work. — Boston  Med. 
and  Surg.  Journal,  April  26,  1S66. 

Dr.  West's  volume  is,  in  our  opinion,  incomparably 
the  best  authority  upon  the  maladies  of  children 
that  the  practitioner  can  consult.  Withal,  too — a 
minor  matter,  truly,  but  still  not  one  that  should  be 
neglected — Dr.  West's  composition  possesses  a  pecu- 
liar charm,  beauty  and  clearness  of  expression,  thus 
aft'ording  the  reader  much  pleasure,  even  independent 
of  that  which  arises  from  the  acquisition  of  valuable 
truths. — Cincinnati  Jour,  of  Medicine,  JUarch,  IStitJ. 

We  have  long  regarded  it  as  the  most  scientific  and 
practical  book  on  diseases  of  children  which  has  yet 
appeared  in  this  country. — Buffalo  Medical  Journal. 

Dr.  West's  book  is  the  best  that  has  ever  been 
written  in  the  English  language  on  the  diseases  of 


rjONBIE  [D.  FRANCIS),  M.D. 


A  PRACTICAL  TREATISE  ON  THE  DISEASES  OF  CHILDREN. 

Fifth  edition,  revised  and  augmented.     In  one  large  octavo  volume  of  over  750  closely- 
printed  pages,  extra  cloth.     $4  50: 


Dr.  Condie's  scholarship,  acumen,  industry,  and 
practical  sen.se  are  manifested  in  this,  as  in  all  his 
numerous  contributions  to  science. — Dr.  Holmes's 
Report  to  the  American  Medical  Association. 

Taken  as  a  whole,  in  our  judgment.  Dr.  Condie's 
treatise  is  the  one  from  the  perusal  of  which  the 
practitioner  in  tbis  country  will  rise  with  the  great- 
est satisfaction  — Western  Journal  of  Medicine  and 
Surgery. 

We  pronounced  the  first  edition  to  be  the  best  work 


on  the  diseases  of  children  in  the  English  language, 
and,  notwithstanding  all  that  has  been  published,  we 
still  regard  it  in  that  light. — Medical  Examiner. 

The  value  of  works  by  native  authors  on  the  dis- 
eases which  the  physician  is  called  upon  to  combat 
will  be  appreciated  by  all,  and  the  work  of  Dr.  Cou- 
die  has  gained  for  itself  the  character  of  a  safe  guide 
for  students,  and  a  useful  work  for  consultation  by 
those  engaged  in  practice. — N.  Y.  Med.  Times. 


rjHURCHILL  [FLEETWOOD),  M.D.,  M.R.LA., 

Prof,  of  Midwifery  and  Diseases  of  Women  and  Children  in  the  Dublin  College  of  Physicians. 

ON   THE   DISEASES    OF   INFANTS   AND    CHILDREN.     Second 

American  edition,  revised  and  enlarged  by  the  author.     Edited,  with  Notes,  by  W.  V. 
Keati>''g,  M.  D.    In  one  large  and  handsome  volume  of  over  700  pages,  extra  cloth.    $4  50. 


D 


E  WEES  (  WILLIAM  P.),  M.  D., 

Late  Professor  of  Mid/ioifery,  &c.,  in  the  University  of  Pennsylvania,  &c. 

A  TREATISE  ON  THE  PHYSICAL  AND  MEDICAL  TREAT- 
MENT OF  CHILDREN.  Eleventh  edition,  with  the  author's  last  improvements  and  cor- 
rections.    In  one  octavo  volume  of  548  pages.     $2  80. 


Henry  C.  Lea's  Publicatioxs — {DiaeaM^  of  Women). 


JlfEIGS  {CHARLES  D.),  M.  D., 

Late  Professor  of  Ohstetrlcx,  &c.  in  Jtffer.inn  Medical  College,  Philadelphia. 

WOMAN:    HER  DISEASES  AXD  THEIR  REMEDIES,     A  Series 

of  Lectures  to  his  Class.     Fourth  and  Improved  edition.     In  one  large  and  beautifully 
printed  octavo  volume  of  over  700  pages,  extra  cloth,  $5  00;  leather,  $6  00. 

That  this  work  has  been  thoroughly  appreciated    mend  with  great  pleasure  a  much  improved  edition 
bv  the  profession  of  this  couDtry  as  well  as  of  Europe,     of  a  work  in  which  wo  «aw  little  room  for  improve- 


is  fally  attested  by  the  fact  of  its  having  reached  its 
fourth  edition  in  a  period  of  less  than  twelve  years. 
Its  value  has  been  much  enhanced  by  many  impor- 
tant additions,  and  it  contains  a  fund  of  useful  in- 
formation, conveved  in  an  easy  and  dpjigbtfnl  style. 
Every  topic  discussed  by  the  author  is  rendered  so 
plain  as  to  be  readily  understood  by  evory  student: 
uud,  for  our  own  part,  we  consider  it  not  only  one  of 
the  most  readable  of  books,  but  one  of  priceless  value 
to  the  practitioner  engaged  in  the  practice  of  those 
diseases  peculiar  to  females. — N.  Aiil.  Med.-Ohir.  Re- 
vie  to. 


We  read  the  book  and  find  him  more- 
tliiuker,  an   eloquent    expounder,    and 


-an  ori.ginal 
a   thorough 


meat. — Na.ihville  Medical  .Tourna.L 

We  greet  this  new  edition  of  Dr.  Metg.5' work  on 
woman  with  much  pleasure,  and  commend  it  to  the 
profession,  especially  to  the  yoanger  members,  who 
may  receive  much  valuable  instruction  from  its 
pages,  conveyed  in  a  pleasing  style.  The  teaching 
throughout  the  work  reflects  the  highest  credit  upon 
the  head  and  heart  of  the  author. — Chicago  Medical 
Jov.rnal. 

The  rules  of  the  art  here  described,  the  obstetrical 
opinions  here  expressed,  the  general  direction^  and 
advice  given  and  suggested,  are,  beyond  any  cavil, 
unexceptionably  sagacious  and  prudent.  They  are 
founded  on  a-large  practice,  have  been  tested  by  i 


practitioner.  The  boo^  is  but  twelve  years  old,  but  i  long  experience,  and  come  from  lips  to  whose  teach- 
it  has  been  so  much  appreciated  by  the  profession  ing  thousands  have  listened  for  many  years,  and 
that  edition  after  edition  has  been  demanded,  and  j  never  without  profit. — CharleUon  Bled.  Journal  and 
now  the  fourth  is  on  the  table  by  us.     We  recom-  J  Review. 

JOT  THE  SAME  A  UTHOR.  

OX  THE  NATURE,  SIG-XS,  AND  TREATMENT  OF  CHILDBED 

FEVER.     In  a  Series  of  Letters  addressed  to  the  Students  of  his  Class.     In  one  handsome 
octavo  volume  of  365  pages,  extra  cloth.     $2  00. 


QEURCHILL  {FLEETWOOD),  M.  D.,  M.  R.  1.  A. 

-    ON  THE  DISEASES    OF  WOMEN;    including  those  of  Pregnancy 

and  Childbed.  A  new  American  edition,  revised  by  the  Author.  With  Notes  and  Additions, 
by  D.  Francis  Condie,  M.  D.,  author  of  "  A  Practical  Treatise  on  the  Diseases  of  Chil- 
dren." With  numerous  illustrations.  In  one  large  and  handsome  octavo  volume  of  768 
pages,  extra  cloth,  $4  00 ;  leather,  $5  00. 

From  the  Author^ s  Preface. 
In  reviewing  this  edition,  at  the  request  of  my  American   publishers,  I  have  inserted  several 
new  sections  and  chapters,  and  I  have  added,  I  believe,  all  the  information  we  have  derived  fromi 
recent  researches ;  in  addition  to  which  the  publishers  have  been  fortunate  enough  to  secure  the 
services  of  an  able  and  highly  esteemed  editor  in  Dr.  Condig. 
As  an  epitome  of  all  that  is  known  in  this  depart-    present  day.     To  Dr.  Churchtll,  then,  are  the  pro- 
fession deeply  indebted  for  supplying  them  with  so 
great  a  desideratum — the  achievement  of  which  de- 
servedly entitles  his  name,  already  intimately  asso- 
ciated with  the  diseases  of  women,  to  rank  very  high 
as  au  authority  upon  this  subject.     We  would  briefly 
characterize  it  as  one  of  the  most  useful  which  has 
issued  from  the  press  for  many  years.     To  all  it  bears 
its  own  recommendation  ;  and  will  be  found  to  be 
invaluable  to  the  student  as  a  text-book,  no  less  than 
as  a  compendious  work  of  reference  to  the  qualified 
practitioner. — Glasgow  Med.  Journal. 


ment  of  medicine,  the  book  before  us  is  perhaps  the 
fullest  and  most  valuable  in  the  English  language. 
— DoMin  Medical  Press. 

It  was  left  for  Dr  Chfrchill  to  gather  the  scat- 
tered facts  from  their  various  soujxes,  and  reduce 
them  to  a  .general  system.  This  he  has  done  with  a 
masterly  hand  in  the  volume  now  before  us ;  in 
which,  to  the  results  of  his  own  extensive  observa- 
tion, he  has  added  the  views  of  all  British  and  for- 
eign writers  of  any  note  ;  thus  giving  us  in  a  com- 
plete form,  all  that  is  known  upon  this  subject  at  the 


B 


T  THE  SAME  A  UTHOR.  

ESSAYS  ON  THE  PUERPERAL  FEVER,  AND  OTHER  DIS- 
EASES PECULIAR  TO  WOMEN.  Selected  from  the  writings  of  British  Authors  previ- 
ous to  the  close  of  the  Eighteenth  Century.  In  one  neat  octavo  volume  of  about  450 
jjages,  extra  cloth.     $2  50. 

'DROWN  {ISAAC  BAKER),  M.  D. 

ON  SOME  DISEASES  OF  WOMEN  ADMITTING  OF  SURGICAL 

TREATMENT.     With  handsome  illustrations.      One  volume  8vo.,  extra  cloth,  pp.   276. 
$]   60. 


An  important  addition  to  obstetrical  literature. 
The  operative  suggestions  and  contrivances  which 
Itlr.  Rrow.n"  describes,  exhibit  much  practical  sagacity 
and  skill,  and  merit  the  careful  attention  of  every 
surgeon-accoucheur. — Association  Journal. 


We  have  no  hesitation  in  recommending  this  book 
to  the  careful  attention  of  all  surgeons  who  make 
female  complaints  a  part  of  their  study  and  practice. 
— Dublin  Quarterly  Journal. 


ASnWELT/S  PR.\CTIC.U.  TREATISE  ON  THE  DIS- 
EA.SES  PECUIJ.^R  TO  WO.MEN.  Illustrated  by 
Cases  df;rived  from  Hospital  and  Private  Practice. 
Third  American,  from  the  Third  and  revised  Lon- 
don edition.  In  one  octavo  volume,  extra  cloth, 
of  o28  pages.     *.3  .00. 

EIOBY  0.\  THE  CONSTITUTIONAL  TRE.^TMENT 
OF  FEMALE  DtHEA.SES.  In  one  neat  royal  ]2mo. 
volume,  extra  cloth,  of  about  2i)0  pages,    tjsl  Ou. 


DEWEES'S  TREATISE  ON  THE  DISEASES  OF  FE- 
iMALES.  With  illustrations.  Eleventh  Edition, 
with  the  Author's  last  improvements  and  correc-- 
tions.  In  one  octavo  volume  of  536  pages,  with 
plates,  extra  cloth,  $.3  00. 

COLO.MBAT  DE  L'ISERE  ON  THE  DISEASES  OF 
FKMAl/ES.  Translated  by  C.  D.  Mmos,  M.  D.  Se- 
cond edition.  In  one  vol.  Rvo,  extra  cloth,  with 
numerous  wood-cuts.    pp.  72U.    $3  75. 


24  Henry  C.  Lea's  Publications — (Diseases  of  Women). 

JJODGE  {HUGH  L.),  31. D. 

OX  DISEASES  PECULIAR  TO  WOMEN;  inclucling  Displacements 

of  the  Uterus.     With  original  illustrations.     In  one  beautifully  printed  octavo  volume  of 
nearly  500  pages,  extra  cloth.     $.3  75. 

CONTENTS. 

PART  I.  Diseases  of  Irritation.— Chapter  I.  Nervous  Irritation,  and  its  consequences. 
II.  Irritable  Uterus — Complications.  III.  Local  Symptoms  of  Irritable  Uterus.  IV.  Local 
Symptoms  of  Irritable  Uterus.  V.  General  Symptoms  of  Irritable  Diseases.  VI.  General 
Symptoms  of  Irritable  Uterus — Reflex  Influences  of  Cerebral  and  Spinal  Irritation.  ■  VII.  Pro- 
gress and  Terminations  of  Irritable  Uterus.  VIII.  Causes  and  Pathology  of  Irritable  Diseases. 
IX.  Treatment  of  Irritable  Uterus — Removal  or  Palliation  of  the  Cause.  X.  Treatment  of 
Irritable  Uterus — to  Diminish  or  Destroy  the  Morbid  Irritability.  XI.  Treatment  of  Irritable 
Uterus — modified  by  Menstrual  Disorders  and  Inflammations.  XII.  Treatment  of  Irritable 
Uterus  Complicated  with  Secondary  and  Sympathetic  Symptoms. 

PART  II.  Displacements  op  the  Uterus. — Chapter  I.  Displacement  of  the  Uterus.  II. 
Causes  and  Symptoms  of  Displacement  of  the  Uterus.  III.  Di.ngnosis  of  Displacement  of  the 
Uterus.  IV.  Treatment  of  Displacement  of  the  Uterus.  V.  Treatment,  continued — Internal 
Supporters.  VI.  Treatment,  continued — Lever  Pessaries.  VII.  Treatment,  continued.  VIII. 
Treatment  of  Complications  of  Displacements. 

PART  III.  Diseases  of  Sedation. — Chapter  I.  General  and  Local  Se'&ation.  II.  Sedation 
of  Uterus.     III.  Diagnosis  and  Treatment. 


EST  [CHARLES),  M.D. 
LECTUKES  ON"  THE  DISEASES  OF  WOMEN.    Second  American, 

from  the  second  London  edition.     In  one  neat  octavo  volume  of  about  500  pages,  extra 
cloth.     $3  25.     • 

"We  liave  thus  embodied,  in  this  series  of  lectures, 
one  of  the  mo.st  valuable  treatises  on  the  diseases  of 
the  female  sexual  system  unconnected  with  ge.station, 
in  our  language,  aad  one  which  cannot  fail,  from  the 
lucid  manner  in  which  the  various  sulijects  have 
been  treated,  and  the  careful  discrimination  n.sed  in 
dealiug  only  with  facts,  to  recommend  the  vulume  to 
the  careful  study  of  every  practitioner,  as  affording 
bis  safest  guides  to  practice  within  our  knowledge. 
We  have  seldom  perused  a  work  of  a  more  thoroughly 
practical  character  than  the  one  before  us.  Every 
page  teems  with  the  most  truthful  aud  accurate  infor- 
mation, and  we  certainly  do  not  know  of  any  other 
work  from  which  the  physician,  in  active  practice, 

nY  THE  SA3fE  AUTHOR.  ,  

AN  ENQUIRY  INTO  THE  PATHOLOGICAL  IMPORTANCE  OP 

ULCERATION  OP  THE  OS  UTERL     In  one  neat  octavo  volume,  extra  cloth.     $1  25. 


can  more  readily  obtain  advice  of  the  soundest  cha- 
racter upon  the  peculiar  diseases  which  have  been 
made  the  subject  of  elucidation. — British  Am,.  Med. 
Journal. 

We  return  the  author  our  grateful  thanks  for  the 
vast  amount  of  instruction  he  has  afforded  us.  His 
valuable  treatise  needs  no  eulogy  &n  our  part.  His 
graphic  diction  and  truthful  pictures  of  disease  all 
speak  for  themselves. — Medico-Ghirurg.  Review. 

Most  justly  esteemed  a  standard  work It 

bears  evidence  of  having  been  carefully  revised,  and 
is  well  woi'thy  of  the  fame  it  has  already  obtained. 
— Dull.  Med.  Quar.  Jour. 


OniPSOiV  [SIR  JAMES  Y.),  M.D. 
CLINICAL  LECTURES  ON  THE  DISEASES  OF  WOMEN.    With 

numerous  illustrations.  In  one  handsome  octave  volume  of  over  500  pages,  extra  cloth.  $4. 
The  principnl  topics  embraced  in  the  Lectures  are  Vesico-Vaginal  Fistula,  Cancer  of  the  Uterus, 
Treatment  of  Carcinoma  by  Caustics,  Dysmenorrhoea,,  Amenorrhoea,  Closures,  Contractions,  &e., 
of  the  Vagina,  Vulvitis,  Causes  of  Death  after  Surgical  Operations,  Surgical  Fever,  Phlegmasia 
Dolens,  Cocoyodinia,  Pelvic  Cellulitis,  Pelvic  Hfematoma,  Spurious  Pregnancy,  Ovarian  Dropsy, 
Ovariotomy,  Cranioclasra,  Diseases  of  the  Fallopian  Tubes,  Puerperal  Mania,  Sub  Involution  and 
Super-Involution  of  the  Uterus,  &e.  &c. 


'DENNET  [HENRY),  31.  D. 
A   PRACTICAL    TREATISE    ON    INFLAMMATION    OP    THE 

UTERUS,  ITS  CERVIX  AND  i\PPBNDAGES,   and  on  its  connection  with  Uterine  Dis- 
ease.   Sixth  American,  from  the  fourth  and  revised  English  edition.    In  one  octavo  volume 
of  about  500  pages,  extra  cloth.     $3  75.     {Recently  Issued.) 
From,  the  Author'' s  Preface. 
During  the  past  two  years,  this  revision  of  former  labors  has  been  my  principal  occupation,  and 
in  its  present  state  the  work  may  be  considered  to  embody  the  matured  experience  of  the  many 
years  I  have  devoted  to  the  study  of  uterine  disease. 


Indeed,  the  entire  volume  is  so  replote  with  infor- 
mation, to  all  appearance  so  perfect  in  its  details,  that 
we  could  scarcely  have  thought  anotlici-  page  or  para- 
graph was  required  for  the  full  descripiiou  of  all  that 
is  now  known  with  regard  to  the  diseases  under  con- 
sideration if  we  had  not  been  so  informed  by  the  au- 


thor. To  speak  of  it  except  in  terms  of  the  highest 
approval  would  be  impossible,  aud  we  gladly  avail 
ourselves  of  the  present  opportunity  to  recommend 
it  in  the  most  unqualified  manner  to  the  profession. 
— Dublin  Med.  Press. 


B 


r  THE  SAME  AUTHOR.  ■ • 

A  REVIEW  OF  THE  PRESENT  STATE  OP  UTERINE  PATHO- 

LOGY.     In  one  small  octavo  volume,  extra  cloth.     60  cents. 


Henry  C.  Lea's  Publications — {Midwifery). 


JJODGE  {HUGH  L.),  M.D., 

Late  Professor  of  Midwifery,  &o.  in  the  University  of  Pennsylvanio,,  &c. 

THE  PRINCIPLES  AND  PRACTICE  OF  OBSTETPJCS.  Illus- 
trated with  large  lithographic  jjlates -containing  one  hundred  and  fifty-nine  figures  from 
original  photographs,  and  with  numerous  wood-cuts.  In  one  large  and  beautifully  printed 
quarto  volume  of  560  double-columned  pages,  strongly  bound  in  extra  cloth,  $14.  (Late- 
ly publislied. ) 

From  the  Author's  Preface. 

"lufluenced  by  these  motives,  the  author  has,  in  this  volume,  endeavored  to  present 

not  simply  his  own  opinions,  but  also  those  of  the  most  distinguished  authorities  in 

the  profession ;  so  that  it  may  be  considered  a  digest  of  the  theory  and  practice  of 

Obstetrics  at  the  present  period." 

In  carrying  out  this  design,  the  ample  space  afforded  by  the  quarto  form  has  enabled  the  author 
to  enter  thoroughly  into  all  details,  and  in  combining  the  results  of  his  long  experience  and  study 
with  the  teachings  of  other  distinguished  authors,  he  cannot  fail  to  afford  to  the  practitioner  what- 
ever counsel  and  assistance  may  be  required  in  doubtful  cases  and  emergencies. 

A  distinguishing  feature  of  the  work  is  the  jirofuseness  of  its  illustrations.  The  lithographic 
plates  are  all  original,  and,  to  insure  their  accuracy,  they  have  been  copied  from  photographs  taken 
expressly  for  the  purpose.  Besides  these,  a  very  full  series  of  engravings  on  wood  v/iJl  be  found 
scattered  through  the  text,  so  that  all  the  details  given  by  the  author  are  amply  elucidated  by  the 
illustrations.  It  may  be  added  that  no  pains  or  expense  have  been  spared  to  render  the  mechanical 
execution  of  the  work  in  every  respect  worthy  of  the  character  and  value  of  the  teachings  it  contains. 

*:5J,*  Specimens  of  the  plates  and  letterpiress  will  be  forwarded  to  any  address  free  by  mail  on 
receipt  of  six  cents  in  postage  stamps. 

The  work  of  Dr.  Hodge  is  something  more  than  a  ]  We  have  examined  Professor  Hodge's  work  with 
simple  presentation  of  hi.s  particular  views  in  the  de-  great  satisfaction  ;  every  topic  is  elaborated  most 
partmeat  of  Obstetrics ;  it  is  something  more  than  an  t'ully.  The  views  of  the  author  are  comprehensive, 
ordinary  treatise  on  midwifery ;  it  is,  in  fact,  a  cyclo-  |  and  concisely  stated.  The  rules  of  practice  are  jildi- 
piBdia  of  midwifery.  He  has  aimed  to  embody  in  a  cious,  and  will  enable  the  practitioner  to  meet  every 
single  volume  the  whole  science  and  art  of  Obstetrics,    emergency  of  obstetric  complication  with  confidence. 


An  elaborate  text  is  combined  with  accurate  and  va- 
ried pictorial  illustrations,  so  that  no  fact  or  principle 
is  left  unstated  or  unexplained. — Am,.  Med.  Times, 
Sept.  3,  1S64. 

Vi^e  should  like  to  analyze  the  remainder  of  this 
excellent  work,  but  already  lias  this  review  extended 
beyond  our  limited  space.  We  cannot  conclude  this 
notice  without  referring  to  the  excellent  finish  of  the 
work.  In  typography  it  is  not  to  be  excelled ;  the 
paper  is  superior  to  what  is  usually  afi'orded  by  our 
American  cousins,  quite  equal  to  the  best  of  English 
books.     The  engravings  and  lithographs   are  most 


-Chicago  Med.  Journal,  Aug.  ISG-f. 

More  time  than  we  have  had  at  our  disposal  since 
we  received  the  great  work  of  Dr.  Hodge  is  necessary 
to  do  it  justice.  It  is  undoubtedly  by  far  the  mos't 
original,  complete,  and  carefully  composed  treatise 
on  the  principles  and  practice  of  Obstetrics  which  has 
ever  been  issued  from  the  American  press. — Pacifie 
Med.  and  Surg.  Journal,  July,  1S64. 

We  have  read  Dr.  Hodge's  book  with  great  plea- 
sure, and  have  much  satisfaction  in  expressing  our 
commendation  of  it  as  a  whole.    It  is  certainly  highly 


beautifully  executed.     The  work  recommends  itself   instructive,  and  in  the  main,  we  believe,  correct.   Th'„ 
for  Its  originality  and  is  in  every  way  a  most  valu-    g,.eat  attention  which  the  author  has  devoted  to  the 


able  addition  to  those  on  the  subject  of  obstetrics. 
CanadM  Med.  Journal,  Oct.  180-t 
It  is  very  large,  profusely  and  elegantly  illustrated. 


mechanism  of  parturition,  taken  along  with  the  con- 
clusions at  which  he  has  arrived,  point,  we  think, 
conclusively  to  the  fact  that,  in  Britain  at  least,  the 


and  is  fitted  to  take  its  place  near  the  works  of  great    doctrines  of  Naegele  have  been  too  blindly  received, 
obstetricians.    Of  the  American  works  on  the  subject    — Glasgow  Med.  Journal,  Oct.  ISCi. 
it  is  decidedly  the  best. — Edinb.  Med.  Jour.,  Dec.  '64.  I 


JfJ^O.VTGOMERY  {W.  F.),  M.D., 

Professor  of  Midwifery  in  the  King's  and  Queen's  College  of  Physicians  in  Ireland. 

AN  EXPOSITION  OF  THE  SIGNS  AND  SYMPTOMS  OF  PREG- 

NAXCY.  "With  some  other  Papers  on  Subjects  connected  with  Midwifery.  From  the  second 
and  enlarged  English  edition.  With  tv/o  exquisite  colored  plates,  and  numerous  wood-outs. 
In  one  very  handsome  octavo  volume  of  nearly  600  pages,  extra  cloth.     §3  75. 


31 


ILLER  [HENRY),  M.D., 

Professor  of  Obstetrics  dad  Diseases  of  Women  and  Children  in  the  University  of  Loui.sville. 

PRINCIPLES  AND  PRACTICE  OF  OBSTETRICS,  &c.;  including 

the  Treatment  of  Chronic  Inflammation  of  the  Cervix  and  Body  of  the  Uterus  considered 
a.s  a  frequent  cau.'-e  of  Abortion.  With  about  one  hundred  illustrations  on  wood.  In  one 
very  handsome  octavo  volume  of  over  600  pages,  extra  cloth.     $o  75. 


TYLER  SMITH  0>'  PARTURITIOI^,  AND  THE  PRIN- 
CIPLES A.VD  PRACTICE  OF  OBSTETRICS.  In 
one  royal  12mo.  volume,  extra  cloth,  of  400  pages. 

RIOBY'S  SYSTEM  OF  MIDWIFERY.  With  Notes 
aud   Additional    IUui<trationii.      Second    American 


edition.  One  volume  octavo,  extra  cloth,  422  page.s. 
$2  .JO. 
DEWEES'R  COMPREHENSIVE  SYSTEM  OF  MID- 
WIFERY. Illustrated  by  occasional  cases  and 
many  eiiijravings.  Twelfth  edition,  with  the  an- 
thor'H  last  irnprovementH  and  corrections.  In  one 
octavo  volume,  extra  cloth,  of  600  pages.    $3  00. 


26 


Henry  C.  Lea's  Publications — {Midwifery). 


UAMSBOTHAM  [FRANCIS  H.),  M.D. 


THE    PRINCIPLES   AND    PRACTICE    OF    OBSTETRIC    MEDI- 

CINE  AND  SURGERY,  in  reference  to  the  Pjocess  of  Parturition.  A  new  and  enlarged 
edition,  thoroughly  revised  by  the  author.  With  additions  by  W.  V.  Keating,  M.I>., 
Professor  of  Obstetrics,  &c.,  in  the  Jefferson  Medical  College,  Philadelphia.  In  one  large 
and  handsome  imperial  octavo  volume  of  650  pages,  strongly  bound  in  leather,  with  raised 
bands;  with  sixty-four  beautiful  plates,  and  numeioas  wood-cuts  in  the  text,  containing  in 
all  nearly  200  large  and  beautiful  figures.     $7  00. 


We  will  only  add  that  the  student  will  learn  from 
it  all  he  need  to  know,  and  the  practitioner  will  find 
it,  as  a  book  of  reference,  surpassed  by  none  other. — 
Stethoscope. 

The  character  and  merits  of  Dr.  Eamsbotham's 
work  are  so  well  known  and  thoroughly  establi.shed, 
that  comment  is  unnecessary  and  praise  superfluous. 
The  illustraiions,  which  are  numerous  and  accurate, 
are  executed  in  the  highest  style  of  art.  We  cannot 
too  highly  recommend  the  work  to  our  readers. — St. 
Louis  Med.  and  Surg.  Journal. 


To  the  physician's  library  it  is  indispensable,  while 
to  the  student,  as  a  text-book,  from  which  to  extract 
the  material  for  laying  the  foundation  of  an  education 
on  obstetrical  science,  it  has  no  superior. — Ohio  Mad. 
and  Surg.  Journal. 

When  we  call  to  mind  the  toil  we  underwent  in 
acquiring  a  knowledge  of  this  subjed,  wo  cannot  but 
envy  the  student  of  the  present  day  the  aid  which 
this  work  will  afford  him. — Am.  Jour,  of  the  Med. 
Sciences. 


AfEIGS  [CHARLES  D.),  M.D., 

Lately  Professor  of  Obstetrics,  &c.,  in  the  Jefferson  Medical  College,  Philadelphia. 

OBSTETRICS:    THE  SCIENCE  AND  THE  ART.     Fotirth  edition, 

revised  and  improved.     With  one  hundred  and  twenty-nine  illustrations.     In  one  beauti- 
fully printed  octavo  volume  of  730  large  pages.     Extra  cloth,  $5  00 ;  leather,  $6  00. 

together  with  the  elevation  of  tone  and  eloquence  in 
style  often  exhibited  by  the  author,  constitute  no 
slight  merit  in  works  on  the  subjects  with  which  the 
author  is  here  occupied  — LoJidun  3Ted    Gazette. 

We  have  made  a  somewhat  careful  examination  of 
this  new  edition  of  the  Science  and  the  Art  of  Obstet- 
rics, and  are  satisfied  that  there  is  no  better  or  more 
useful  guide  to  the  educated  practitioner. — J^aW  Or- 
leans Monthly  Med.  Register. 


We  have,  therefore,  great  satisfaction  in  bringing 
under  our  readers'  notice  the  matured  views  of  the 
higliest  American  authority  in  the  department  to 
which  he  has  devoted  his  life  and  talents.  They  com- 
prise not  only  the  "fruit  of  many  years  of  painful  (oil 
in  the  aciiui>ition  of  clinical  e.Kporience  and  know- 
ledge," but  tln'y  Contain  also  the  evidences  of  an 
extended  acquaintance  with  European  medical  lite- 
rature, both  continental  and  British.     This  feature. 


riHURCHILL  [FLEETWOOD),  M.D.,  M.R.LA. 
ON  THE  THEORY  AND  PRACTICE  OF  MIDWIFERY.     A  new 

American  from  the  fourth  revised  and  enlarged  London  edition.  With  notes  and  additions 
by  D.  Francis  Condie,  M.  D.,  author  of  a  "Practical  Treatise  on  the  Diseases  of  Chil- 
dren,'' <fec.  With  one  hundred  and  ninety- four  illustrations.  In  one  very  handsome  octavo 
volume  of  nearly  700  large  pages.     Extra  cloth,  $4  00  j  leather,  $5  00. 

In  adapting  this  standard  favorite  to  the  wants  of  the  profession  in  the  United  States,  the  editor 
has  endeavored  to  insert  everything  that  his  experience  has  shown  him  would  be  desirable  for  the 
American  student,  including  a  large  number  of  illustrations.  With  the  sanction  of  the  author, 
he  has  added,  in  the  form  of  an  appendix,  some  chapters  from  a  little  "  Manual  for  Midwives  and 
Nurses,"  recently  issued  by  Dr.  Churchill,  believing  that  the  details  there  presented  can  hardly 
fail  to  prove  of  advantage  to  the  junior  practitioner.  The  result  of  all  these  additions  is  that  the 
work  now  contains  fully  one-half  more  matter  than  the  last  American  edition,  with  nearly  one- 
half  more  illustrations;  so  that,  notwithstanding  the  use  of  a  smaller  type,  the  volume  contains 
almost  two  hundred  pages  more  than  before. 

No  effort  has  been  spared  to  secure  an  improvement  in  the  mechanical  execution  of  the  work 
equal  to  that  which  the  text  has  received,  and  the  volume  is  confidently  presented  as  one  of  the 
handsomest  that  has  thus  far  been  laid  before  the  American  profession  ;  while  the  very  low  price 
at  which  it  is  ottered  should  secure  for  it  a  place  in  every  lecture-room  and  on  every  office  table. 


These  additions  render  the  work  still  more  com- 
plete and  acceptable  tliaa  ever;  and  with  the  excel- 
lent style  in  which  the  publishers  have  presented 
this  edition  of  Churchill,  we  can  comuiend  it  to  the 
profession  with  great  cordiality  and  pleasure. — Cin- 
cbuiati  Lancet. 

Few  wiu'ks  on  this  branch  of  medical  science  are 
equal  to  it,  certainly  none  excel  it,  whether  in  regard 
to  theory  or  practice,  and  in  one  respect  it  is  superior 
to  all  others,  viz.,  in  its  statistical  information,  and 
therefore,  on  these  grounds  a  most  valuable  work  for 
the  physician,  student,  or  lecturer,  all  of  whom  will 
find  in  it  the  information  which  they  are  seeking  — 
Brit.  Am.  Journal. 

The  present  treatise  is  very  much  feniarged  and 
amplified  beyond  the  previous  editions,  but  nothing 


has  been  added  which  could  be  well  dispensed  with. 
An  examination  of  the  table  of  contents  shows  how 
thoroughly  the  author  has  gone  over  the  ground,  and 
the  caie  he  has  taken  in  the  text  to  present  the  sub- 
jects in  all  their  bearings,  will  render  this  new  edition 
even  moie  necessary  to  the  obstetric  student  than 
were  either  of  the  former  editions  at  the  date  of  their 
appearance.  No  treatise  on  obstetrics  with  which  we 
are  acquainted  can  compare  favorably  with  this,  in 
respect  to  the  amount  of  material  which  has  been 
gathered  from  every  source. — Boston  Mtd.  and  Surg. 
Journal. 

There  is  no  better  text-book  for  students,  or  work 
of  reference  and  study  for  the  practising  physician 
than  this.  It  should  adorn  and  enrich  every  medical 
library. — Chicago  Med.  Journal. 


Henry  C.  Lea's  Publications — (Surgery). 


2t 


fiROSS  [SAMUEL  D.),  M.D., 

Professor  of  Surgery  in  the  Jefferson  Medical  College  of  Philadelphia. 

A  SYSTEM  OF  SURGERY:    Pathological,  -Diagnostic,  Therapeutic, 

and  Operative.    Illustrated  by  upwards  of  Thirteen  Hundred  Engravings.    Fourth  edition, 
carefully  revised,  and  improved.    In  two  large  and  beautifully  printed  royal  octavo  volumes 
of  2200  pages,  strongly  bound  in  leather,  with  raised  bands.     $16  00. 
The  continued  favor,  shown  by  the  exhaustion  of  successive  large  editions  of  this  great  work, 
proves  that  it  has  successfully  supplied  a  want  felt  by  American  practitioners  and  students.    Though 
but  little  over  six  years  have  elapsed  since  its  first  publication,  it  has  already  reached  its  fourth 
edition,  while  the  care  of  the  author  in  its  revision  and  correction  has  kept  it  in  a  constantly  im- 
proved shape.     By  the  use  of  a  close,  though  very  legible  type,  an  unusually  large  amount  of 
matter  is  condensed  in  its  pages,  the  two  volumes  containing  as  much  as  four  or  five  ordinary 
octavos.     This,  combined  with  the  most  careful  mechanical  execution,  and  its  very  durable  binding, 
renders  it  one  of  the  cheapest  works  accessible  to  the  profession.     Every  subject  properly  belonging 
to  the  domain  of  surgery  is  treated  in  detail,  so  that  the  student  who  possesses  this  work  may  be 
said  to  have  in  it  a  surgical  library. 


It  must  long  remain  the  most  comprehensive  work 
on  this  important  part  of  medicine. — Bostori  Ifedical 
and  Surgical  Journal,  March  23,  1865. 

We  have  compared  it  with  most  of  our  standard 
works,  Xach  as  those  of  Erichsen,  Miller,  Pergusson, 
Syme,  and  others,  and  we  must,  in  justice  to  our 
author,  award  It  the  pre-eminence.  As  a  work,  com- 
plete iu  almost  evei'y  detail,  no  matter  bow  minute 
or  trifling,  and  embracing  every  subject  known  in 
the  principles  and  practice  of  surgery,  we  believe  it 
stands  without  a  rival.  Dr.  Gross,  in  his  preface,  re- 
marks "ray  aim  has  been  to  embrace  the  whole  do- 
main of  surgery,  and  to  allot  to  every  subject  its 
legitimate  claim  to  notice;"  and,  we  assure  our 
readers,  he  has  kept  his  word.  It  is  a  work  which 
we  can  most  confidently  recommend  to  our  brethren, 
for  its  utility  is  becoming  the  more  evident  the  longer 
it  is  upon  the  shelves  of  our  library. — Canada  Med. 
Joiirnal,  September,  1865. 

The  first  two  editions  of  Professor  Gross'  System  of 
Surgery  are  so  well  known  to  the  profession,  and  so 
highly  prized,  that  it  would  be  idle  for  us  to  speak  in 
praise  of  this  work. —  Chicago  Medical  Joii/rnal, 
"September,  1865. 

We  gladly  indorse  the  favorable  recommendation 
of  the  work,  both  as  regards  matter  and  style,  which 
we  made  when  noticing  its  first  appearance. — British 
and  Foreign  Medico- Chirurgical  Bevievj,  Oct.  1865. 

The  most  complete  work  that  has  yet  issued  from 
the  press  on  the  science  and  practice  of  surgery. — 
London  Lancet. 

This  system  of  surgery  is,  we  predict,  destined  to 
take  a  commanding  position  in  our  surgical  litera- 
ture, and  be  the  crowning  glory  of  the  author's  well 
earned  fame.  As  an  authority  on  general  surgical 
subjects,  this  work  is  long  to  occupy  a  pre-eminent 
place,  not  only  at  home,  but  abroad.  We  have  no 
hesitation  in  pronouncing  it  without  a  rival  in  our 
language,  and  equal  to  the  best  systems  of  surgery  in 
any  language. — N.  Y.  Med.  Journal. 

Kot  only  by  far  the  best  text-book  on  the  subject, 
as  a  whole,  within  the  reach  of  American  students, 
but  one  which  will  be  much  more  than  ever  likely 
to  be  resorted  to  and  regarded  as  a  high  authority 
abroad. — Am.  Journal  Med,.  Sciences,  Jan.  1865. 

The  work  contains  everything,  minor  and  major, 
operative  and  diagnostic,  including  mensuration  and 
examination,  venereal  diseases,  and  utei'ine  manipu- 
lations and  operations.  It  is  a  complete  Thesaurus 
o<'  modern  surgery,  where  the  student  and  practi- 

-DY  TEE  SAME  AUTHOR.  

A  PRACTICAL    TREATISE    O^   THE    DISEASES,   INJURIES, 

AND  MALFORxMATlONS  OF  THE  URINARY  BLADDER,  THE  PROSTATE  GLAND, 
AND  THE  URETHRA.  Second  edition,  revised  and  much  enlarged,  with  one  hundred 
and  eighty-four  illustrations.  In  one  large  and  very  handsome  octavo  volume,  of  over  nine 
hundred  jiage.s,  extra  cloth.     $4  00. 


tioner  shall  not  seek  in  vain  for  what  they  desire. — 
San  Francisco  Med.  Press,  Jan.  1865. 

Open  it  where  we  may,  we  find  sound  practical  in- 
formation conveyed  in  plain  language.  This  book  i.s 
no  mere  provincial  or  even  naiional  system  of  sur- 
gery, but  a  work  which,  while  very  largely  indebted 
to  the  past,  has  a  strong  claim  on  the  gratitude  of  the 
future  of  surgical  science. — Edinburgh  Med.  Journal, 
Jan.  1865. 

A  glance  at  the  work  is  .sufficient  to  show  that  the 
author  and  publisher  have  spared  no  labor  in  making 
it  the  most  complete  "System  of  Surgery"  ever  puli- 
lished  in  any  country. — St.  Louis  Med.  and  Surg. 
Journal,  April,  1S65. 

The  third  opportunity  is  now  offered  during  our 
editoi-ial  life  to  review,  or  rather  to  indorse  and  re- 
commend this  great  American  work  on  Surgery. 
Upon  this  last  edition  a  great  amount  of  labor  has 
been  expended,  though  to  all  others  except  the  author 
the  work  was  regarded  in  its  previous  editions  as  so 
full  and  complete  as  to  be  hardly  capable  of  improve- 
ment. Every  chapter  has  been  revised ;  the  text  aug- 
mented by  nearly  two  hundred  pages,  and  a  con- 
siderable number  of  wood-cuts  have  been  introduced. 
Many  portions  have  been  entirely  re-written,  and  the 
additions  made  to  the  text  are  principally  of  a  prac- 
tical character.  This  comprehensive  treatise  upon 
surgery  has  undergone  revisions  and  enlargements, 
keeping  pace  with  the  progress  of  the  art  and  science 
of  surgery,  so  that  whoever  is  in  possession  of  this 
work  may  consult  its  pages  upon  any  topic  embraced 
within  the  scope  of  its  department,  and  rest  satisfied 
that  its  teaching  is  fully  up  to  the  present  standard 
of  surgical  knowledge.  It  is  also  so  comprehensive 
that  it  may  truthfully  be  said  to  embrace  all  that  is 
actually  known,  that  is  really  of  any  value  in  the 
diagnosis  and  treatment  of  surgical  diseases  and  acci- 
dents. Wherever  illustration  will  add  clearness  to  the 
subject,  or  make  better  or  more  lasting  impression,  it 
is  not  wanting;  in  this  respect  the  work  is  eminently 
superior. — Buffalo  Med.  Journal,  Dec.  186i. 

A  system  of  surgery  which  we  think  unrivalled  in 
our  language,  and  which  will  indelibly  associate  his 
name  with  sui'gical  .science.  And  what,  in  our  opin- 
ion, enhances  the  value  of  the  work  is  that,  while  the 
practising  siirgeon  will  find  all  that  he  requires  in  it, 
it  is  at  the  same  tin\e  one  of  the  most  valuable  trea- 
tises which  can  be  put  into  the  hands  of  the  student 
seeking  to  know  the  principles  and  practice  of  this 
brancli  of  the  profession  which  he  designs  subse- 
quently to  follow. — The  Brit.  Am.  Journ.,  Montreal. 


Whoever  will  peruse  the  vast  amount  of  valuable 
practical  information  it  contains  will,  we  tiiiuk,  agree 
with  OS,  that  there  is  no  work  in  the  English  lan- 


guage which  can  make  any  just  pretensions  to  be  its 
equal. ^-iV.  Y.  Journal  of  Medicine. 


pY  THE  SAME  AUTHOR.  

A  PRACTICAL    TREATISE    OX    FOREIGN    BODIES   IN  TUB 

AIR-PABSAGES.       In    one   hand.'ome   octavo   volume,    extra  cloth,    with   illustrations. 
pp.  468.     $2  75. 


2S 


Henry  C.  Lea's  Publications — {Surgery). 


WRICHSEN  {JOHN), 

Professor  of  Surgery  in  University  College,  London. 

THE  SCIENCE  AND  ART  OF  SURGERY;  being  a  Treatise  on  Sur- 

gical  Injuries,  Diseases,  and  Operations.     New  and  improved  American,  from  the  Second 
.  enlarged  and  carefully  revised  London  edition.     Illustrated  with  over  four  hundred  wood 

engravings.     In  one  large  and  handsome  octavo  volume  of  1000  closely  printed  pages  f  extra 

cloth,  §6;  leather,  raised  bands,  $7. 
We  are  bound  to  state,  aad  we  do  so  without  wish-  !  to  give  it  but  a  passing  notice  totally  unworthy  of  its 
ing  to  draw  invidious  comparisons,  that  the  worli  of  merits.  It  may  be  confidently  asserted,  that  no  work 
Mr.  Erichsen,  in  most  respects,  surpasses  any  that  j  on  the  science  and  art  of  surgery  has  ever  received 
has  preceded  it.  Blr  Erichsen's  Is  a  practical  worlc,  \  more  u.niversal  commendation  or  occupied  a  higher 
combining  a  due  proportion  of  the  "Science  and  Art  position  as  a  general  text-book  on  surgery,  than  this 
of  Surgery."     Having  derived  no  little  instruction    treatise  of  Professor  Erichsen. — Savannah  Journal  of 


from  it,  in  many  important  branches  of  surgery,  we 
can  have  no  hesitation  in  recommending  it  as  a  valu- 
able book  alike  to  the  practitioner  and  the  student. 
—  Dublin  Quarterly. 


jiledicine. 

In  fulness  of  practical  detail  and  perspicuity  of 
style,  convenience  of  arrangement  and  soundness  of 
discrimination,  as  well  as  fairness  and  completenes 


Gives  a  very  admirable  practical  view  of  the  sci-    of  discussion,  it  is  better  suited  to  the  wants  of  both 
ence  and  art  of  surgery. — Edinburgh  Med.  and  Surg,     student  and  practitioner  than  any  of  its  predecessors. 


Journal. 

We  recommend  it  as  the  best  compendium  of  sur- 
gery in  our  language. — London  Lancet. 

It  is,  we  think,  the  most  valuable  practical  work 
on  surgery  in  existence,  both  for  young  and  old  prac- 
titioners.— Nashville  3Ied.  and  Surg.  Journal 

The  limited  time  we  have  to  review  this  improved 


-Am.  Journal  of  3Ied.  Sciences. 
After  careful  and  frequent  perusals  of  Erichsen's 
surgery,  we  are  at  a  loss  fully  to  express  otir  admira- 
tion of  it.  The  author's  style  is  eminently  didactic, 
and  characterized  by  a  most  admirable  directness, 
clearness,  and  compactness.  These  traits  have  en- 
abled him.  in  a  volume  of  about  1000  pages,  largely 
occupied  by  wood-cuts,  to  present  what  is,  in  many 


edition  of  a  work,  the  first  issue  of  which  we  prized  respects,  the  most  full  and  complete, systematic  trea- 
.  as  one  of  the  very  best,  if  not  the  best  text-book  of  tise  on  the  siibjecf  of  which  it  treats  in  the  Euglijh 
surgery  with  which  we  were  accxuainted,  permits  us    language. — Ohio  Med.  and  Surg.  Journal. 


j\£ILLER  [JAMES), 

Late  Professor  of  Surgei-y  in  the  University  of  Edinburgh,  &c. 

PRINCIPLES  OF  SURGERY.     Fourth  American,  from  the  third  and 

revised  Edinburgh  edition.  In  one  large  and  very  beautiful  volume  of  700  pages,  with 
two  hundred  and  forty  illustrations  on  wood,  extra  cloth.     %?j  lb. 

Y  THE  SAME  AUTHOR.  

THE    PRACTICE    OF    SURGERY.     Fourth  American,  from  the  last 

Edinburgh  edition.  Revised  by_the  American  editor.  Illustrated  by  three  hundred  and 
sixty-four  engravings  on  wood.  In  one  large  octavo  volume  of  nearly  700  pages,  extra 
cloth.     $3  75. 

It  is  seUlum  that  two  volumes  have  ever  made  so  acquired.    The  author  is  an  eminently  sensible,  prac- 

profound  an  impression  in  so  short  a  time  as  the  tical,  and  well-informed  man,  who  knows  exactly 

"Principles"  and  the  "  Practice"  of  Surgery  by  Mr.  what  he  is  talking  about  and  exiictiy  how  to  talk  it. 

Miller,  ov  so  richly  merited  the  reputation  they  have  — Kentucky  Medical  Recorder. 


B 


JpiRRIE  [WILLTAM),  F.  R.  S.  E., 

Professor  of  Surgery  in  the  University  of  Aberdeen. 

THE  PRINCIPLES  AND  PRACTICE  OF  SURGERY.     Edited  by 

JohxNeill,  M.  D.,  Professor  of  Surgery  in  the  Penna.  Medical  College,  Surgeon  to  the 
Pennsylvania  Hospital,  &c.  In  one  very  handsome  octavo  voltime  of  7bO  pages,  with  316 
illustrations,  extra  cloth.     $3  75. 

We  know  of  no  other  surgical  work  of  reasonable  I  or  where  subjects  are  more  soundly  or  clearly  taught, 
size,  wherein  there  is  so  much  theory  aud  practice,  |  — 2Vie  Stethoscope. 


(^ARGENT  (F.  W.),  M.  D. 


ON  BANDAGING  AND  OTHER  OPERATIONS  OF  MINOR  SUR- 

GERY.    New  edition,  with  an  additional  chapter  on  Military  Surgery.     One  handsome  royal 
12mo.  volume,  of  nearly  400  pages,  with  184  wood-cuts.     Extra  cloth,  $1  75. 


Exceedingly  convenient  and  valuable  to  all  mem- 
bers of  the  profession. — Chicago  Medical  Examiner, 
May,  1S62. 

The  very  best  manual  of  Minor  Surgery  we  have 
seen. — Buffalo  Med.  Journal. 


We  cordially  commend  this  volume  as  one  which 
the  medical  student  should  mo^st  closely  study ;  and 
to  the  surgeon  in  practice  It  mu.st  prove  itself  instruct- 
ive on  many  points  which  he  may  have  forgotten.— 
Brit.  Am.  Journal,  May,  1362. 


MALGAIGNE'S  OPERATIVE  SUEGEET.     With  nu- 
merous illustrations  on  wood.     In  one  handsome 
octavo  volume,  extra  cloth,  of  nearly  600  pp.    $2  oO. 
SKEY'S  OPEEATIVE  SURGERY.    In  one  very  haird- 
.    some  octavo  volume,  extra  cloth,  of  over  6.50  pages, 
with  about  100  wood-cuts.    $3  25. 


FEEGUSSON'S  SY.STEM  OF  PRACTICAL  SUEGEET. 
Fourth  American,  from  the  third  and  enlarged  Lon- 
don edition.  la  one  large  aud  beautifully  printed 
octavo  volume  of  about  700  pages,  with  393  liand- 
some  illustrations.     Leather,  $1. 


Henry  C.  Lea's  Publications — {Surgery). 


29 


'^RDITT  {ROBERT),  M.R.C.S.,  §-c. 
THE  PRINCIPLES  AND   PRACTICE  OF  MODERN  SURGERY. 

A  new  and  revised  American,  from  the  eighth  enlarged  and  improved  London  edition.  Illus- 
trated with  fonr  hundred  and  thirty -two  wood- engravings.  In  one  very  handsome  octavo 
volume,  of  nearly  700  large  and  closely  printed  pages.    Extra  cloth,  $4  00;  leather,  $5  00. 


All  that  the  surgical  student  or  practitioner  could 
desire. — Dublin  Quarterly  Journal. 

It  is  a  most  admirable  book.  We  do  not  know 
when  we  have  exainined  nne  with  more  pleasure.' — 
Boatoii  Med.  and  Sarg.  Journal. 

In  Mr.  Druitt's  bouk,  though  confaining  only  some 
seven  hundred  pages,  both  the  principles  and  the 
practice  of  surgery  are  treated,  and  so  clearly  and 
perspicuously,  as  to  elucidate  every  important  topic. 
The  fact  that  twelve  ediiions  have  already  been  called 

for,  in  these  days  of  active  competition,  would  of  every  medical  student, 
itself  show  it  to  possess  marked  superiority.  We  and  Review. 
have  examined  the  book  must  thoroughly,  and  can 
say  that  this  success  is  well  merited.  His  book, 
moreover,  possesses  the  iuestimable  advantages  of 
haviug  the  subjects  perfectly  well  arranged  and  clas- 
sified, and  of  being  written  in  a  style  at  once  clear 
and  succinct. — Ain.  Journal  of  Med.  Sciences. 


theoretical  surgical  opinions,  no  work  that  we  are  at 
present  acqniiinted  with  can  at  all  cumpare  with  it. 
It  is  a  compendium  of  surgical  theory  (if  we  may  u.-e 
the  word)  and  practice  in  itself,  and  well  deserves 
the  estimate  placed  upon  it. — Brit.  Am.  Journal. 

Thus  enlarged  and  improved,  it  will  continue  to 
rank  among  our  best  text-books  on  elementary  sur- 
gery.— Columhu.i  Rev.  of  Med.  and  Surg. 

We  must  close  this  brief  notice  of  an  admirable 

work  by  recommending  it  to  the  earnest  attention  of 

Charleston  Medical  Journal 


A  text-book  which  the  general  voice  of  the  profes- 
sion in  both  England  and  America  has  commended  as 
one  of  the  most  admirable  "manuals,"  or,  "  vude 
mecum."  as  its  English  title  runs,  wbich  can  be 
placed  in  the  hands  of  the  student.  The  merits  of 
Druitt's  Surgery  are  too  well  known  to  every  one  to 


Whether  we  view  Druitt's  Surgery  as  a  guide  to    need  any  further  eulogium  from  us. — Nashville  Med. 
operative  procedures,  or  as  representing,  the  latest    Journal. 


TJAMILTON  [FRANK  K),  M.D., 

Professor  of  Fractures  and  Dislocations,  &c.  in  Bellevue  Hosp.  Med.  Qollege,  New  TorJc. 

A  PRACTICAL  TREATISE    ON   FRACTURES  AND   DISLOCA- 

TIONS.  Third  edition,  thoroughly  revised.  In  one  large  and  handsome  octavo  volume, 
with  several  hundred  illustrations.  {Preparing  for  early  jniblication.) 
The  demand  which  has  so  speedily  exhausted  two  large  editions  of  this  work  shows  that  the 
author  has  succeeded  in  supplying  a  want,  felt  by  the  profession  at  large,  of  an  exhaustive  treatise 
on  a  frequent  and  troublesome  class  of  accidents.  The  unanimous  voice  of  the  profession,  abroad 
as  well  as  at  home,  has  pronounced  it  the  mo.st  complete  work  to  which  the  surgeon  can  refer  for 
information  respecting  all  details  of  the  subject.  In  the  preparation  of  this  new  edition,  the 
author  has  sedulously  endeavored  to  render  it  worthy  a  continuance  of  the  favor  which  has  been 
recorded  to  it,  and  the  experience  of  the  recent  war  has  afforded  a  large  amount  of  material  which 
he  has  sought  to  turn  to  the  best  practical  account. 

this  work;  to  do  so  would  carry  us  far  beyond  the 
limits  which  we  have  assigned  to  us,  to  say  nothing 
of  the  fact  tliat  it  would  be  a  matter  of  supererogation, 
inasmuch  as  no  intelligent  practitioner  will  be  likely 
to  be  without  a  copy  of  it  for  ready  use.  No  library, 
'hoM'ever  extensive,  will  be  complete  without  it.— 
North  American  Medico- Ghirurgical  Review. 

This  is  a  valuable  contribution  to  the  surgery  of 
most  important  aifections,  and  is  the  more  welcome, 
inasmuch  as  at  the  present  time  we  do  uot  possess  a 
single  complete  treatise  on  Fractures  and  Dislocations 
in  the  English  language.  It  has  remained  for  our 
I  American  brother  to  produce  a  complete  treatise  upon 


The  volume  before  us  is  (we  say  it  with  a  pang  of 
wounded  patriotism)  the  best  and  handiest  book  on 
the  subject  in  the  English  language.  It  is  in  vain  to 
attempt  a  review  of  it ;  nearly  a.s  vain  to  seek  for  any 
gins,  either  of  commission  or  omission. — Edinburgh 
Med.  and  Surg.  JournuX. 

From  the  great  labor  and  time  bestowed  upon  its 
preparation,  we  had  been  led  to  anticipate  a  very 
thorough  and  elaborate  monograph,  and  an  attentive 
perusal  of  its  pages  has  satisfied  us  that  our  expecta- 
tions have  been  fully  realized.  The  work  is  by  far 
the  most  complete  disquisition  on  fractures  and  dis- 
locations in  the  English  language.     It  is  not  our  in- 


tention to  present  anything  like  a  formal  analysis  of  !  the  subject. — London  Lancet. 


nURLING  {T.B.),  F.R.S., 

Surgeon  to  the  London  Hospital,  President  of  the  Hunterian  Society,  &'C. 

A  PRACTICAL   TREATISE   ON  DISEASES   OF   THE   TESTIS, 

SPERMATIC  CORD,  AND  SCROTUM.  Second  American,  from  the  second  and  enlarged 
En>rli,sh  edition.  In  one  handsome  octavo  volume,  extra  cloth,  with  numerous  illustra- 
tions,    pp.  420.     $2  00. 


B 


A  R  WELL  {RICHARD),  F.  R.  G.  S., 

Assistant  Surgeon  Oharing  Cross  Ho.rpital,  &r. 

A  TREATISE  ON  DISEASES  OF  THE  JOINTS.     Illustrated  with 

enjjravings  on  wood.    In  one  very  handsome  octavo  volume  of  about  500  pages ;  extra  cloth, 


BP.ODIE'S  CI.INICAL   LECTURES   ON    SURGERY. 
i  Vol.  &V0.,  3o0  pp.;  clolh,  $1  25. 

COOPER  OJf  THE  STRUCTURE  AND  DISEASES  OF 

THETR-rTlif,    A.VI)  0.V  THB  THyilDS   Gl.AWB.       Oue  VOl. 

imperial  8vo.,  extra  cloth,  with  177  figares  on  29 
pla.Le».    $2  90. 


COOPER'S  LECTURES  ON  THB  PRINCIPLES  AND 
PiiACTiCK  oi'  SuRORiwr.  In  one  very  large  octavo 
volume,  extra  cloth,  of  700  pages.    $2  00. 

GIBSON'S  INSTITUTES  AND  PRACTICE  OF  SUK- 
(iiJuY.  Kiglilh  edition,  improved  and  altered.  With 
tliiriy-four  plates.  In  ,two  liandsonio  octavo  voP 
uni ';.•:,  about  lOUO  pages,  leather,  raised  bauds.  $6  .JO. 


30  Henry  C.  Lea's  Publications — (Surgery). 

mOYNBEE  [JOSEPH],  F.  R.  S., 

Aural  Surgeon  to  and.  Lecturer  on  Surgery  at  St.  Mary''s  Hospital. 

THE  DISEASES  OF  THE  EAR:  their  Nature,  Diagnosis,  and  Treat- 

ment.     With  one  hundred  engravings  on  wood.     Second  American  edition.     In  one  very 
handsomely  printed  octavo  volume  of  440  pages ;  extra  cloth,  $4. 


The  appearance  of  a  volume  of  Mr.  Toynbee's,  tliere- 
foi'e,  iu  which  the  subject  of  aiival  disea.se  is  treated 
in  the  most  scientific  manner,  and  our  linowledge  in 
respect  to  it  placed  fully  on  a  par  with  that  which 
we  possess  respecting  most  other  organs  of  the  body, 
is  a  matter  for  .sincere  congratulation.  We  may  rea- 
sonably hope  that  henceforth  the  subject  of  this  trea- 
tise will  cease  to  be  araoug  the  opproiria  of  medical 
science. — London  Medical  Review. 


The  work,  as  was  stated  at  the  outset  of  our  notice, 
is  a  model  of  its  kind,  and  every  page  and  paragraph 
of  it  are  worthy  of  the  most  thorough  study.  Con- 
sidered all  in  all — as  an  original  work,  well  written, 
philosophically  elaborated,  and  happily  illustrated 
with  cases  and  drawings — it  is  by  far  the  ablest  mo- 
nograph that  has  ever  appeared  on  the  aiiat^imy  and 
diseases  of  the  ear,  and  one  of  the  most  valuable  cou- 
tributious  to  the  art  and  science  of  surgery  iu  the 
nineteenth  century. — N.  Am.  Med.-C/iirurg.  Reoieio. 


TA  URENCE  [JOHN  Z.),  F.  R.  C.  S.,     and      MOON  [ROBERT  C), 

Editor  of  the  OpMhalmic  Jieview,  &e.  Sou.se  Surgeon  to  the  Southwark  Oph- 

thalmic Hospital,  &c. 

A  HANDY-BOOK   OF    OPHTHALMIC    SURGERY,  for  the  use  of 

Practitioners.    With  numerous  illustrations.    In  one  very  handsome  octavo  volume.      {Jiist 
Ready .) 

(from  the  authors'  preface.) 
"In  writing  these  pnges  it  has  been  our  aim  to  bring  the  principles  and  practice  of  modern 
ophthalmic  surgery  within  a  small  compass,  to  supply  the  wants  of  the  busy  practitioner,  who 
may  have  neither  time  nor  opportunity  to  read  the  innumerable  contributions  that  ophthalmic 
surgery  and  science  have  received  within  the  last  fifteen  years. 

"In  describing  symptoms,  we  have  limited  ourselves  to  those  which  are  essential  for  the  recog- 
nition of  disease  ;  in  describing  operations,  <tc.,  to  those  details  which  are  essential  for  its  treat- 
ment. ' ' 

TONES  [T.  WHARTON),  F.  R.  S., 

Professor  of  Ox:>hthalmic  Jled.  and  Surg,  in  University  College,  London. 

THE  PRINCIPLES  AND  PRACTICE  OF  OPHTHALMIC  MEDI- 
CINE AND  SURGERY.  With  one  hundred  and  seventeen  illustrations.  Third  and  re- 
vised American,  with  Additions  from  the  second  London  edition.  In  one  handsome  octavo 
volume  of  455  pages,  extra  cloth.     $3  25. 

We  know  ofno  work  which  contains  the  same  amount  I  It  is  an  excellent  pi'actical  treatise  on  the  medical 
of  information  in  the  same  compass;  we  especially  re-  |  and  sui'gical  diseases  of  the  eye,  and  is  well  adapted 
commend  the  book  to  the  Americau  physician  and  me-  I  to  the  wants  both  of  the  student  and  practitioner. — 
dical  student. — Sa'n  Francisco  Med.  Press.  \  Chicago  Med.  Examiner. 


M 


ACKENZIE  [W.],  M.D., 

Surgeon  Oculi.st  in  Scotland  in  ordinary  to  her  Majesty,  &o. 

A  PRACTICAL  TREATISE  ON  DISEASES  AND  INJURIES  OF 

THE  EYE.  To  which  is  prefixed  an  Anatomical  Introduction  explanatory  of  a  Horizontal 
Section  of  the  Human  Eyeball,  by  Thomas  Wharton  Jones,  F.  R.  S.  From  the  fourth 
revised  and  enlarged  London  edition.  With  Notes  and  Additions  by  Addinell  Hewsox, 
M.  D.,  Surgeon  to  Wills  Hospital,  &e.  .tc.  In  one  very  large  and  handsome  octavo  volume 
of  1027  pages,  extra  cloth,  with  plates  and  numerous  wood-cuts.     $6  60. 


BORLAND  [VV.  W.),  31.  D. 


DISEASES  OF  THE  URINARY  ORGANS;  a  Compendium  of  their 

Diagnosis,  Pathology,  and  Treatment.     With  illustrations.     In  one  large  and  handsome 
octavo  volume  of  about  600  pages,  extra  cloth.     $3  50. 
Taken  as  a  whole,  we  can  recommend  Dr.  Morland's  I  of  every  medical  or  surgical  practitioner. — Brit,  and 
conipendiumasavery  desirableaddltionto  thelibrary  |  For.  Med.-Ohir.  JRevieu),  April,  18.39. 


ASHTON  [T.  J.) 


ON  THE   DISEASES,  INJURIES,  AND  MALFORMATIONS    OF 

THE  RECTUM  AND  ANUS;  with  remarks  on  Habitual  Constipation.  Second  American, 
from  the  fourth  and  enlarged  London  edition.  With  handsome  illustrations.  In  one  very 
beautifully  printed  octavo  volume  of  about  -300  pages.     $3  25.      {Just  Issued.) 

We  can  recommend  this  volume  of  Mr  Ashton's  in 
the  strongest  terras,  as  contaiuing  all  tlie  latest  details 
of  the  pathology  and  treafmeut  of  diseases  connected 
with  the  rectum. — Canada  3Ied.  Journ.,  March,  ISIjH. 

This  is  a  new  and  carefully  revised  edition  of  one 
of  the  most  valuable  special  treatises  that  the  phy- 
sician and  surgeon  can  have  in  his  library. — Chicago 
Medical  Examiner,  Jan.  1S66, 


The  short  period  which  has  elapsed  since  the  ap- 
pearance of  the  former  American  reprint,  and  the 
numerous  editi.uis  published  in  England,  are  the  best 
arguments  we  can  otier  of  the  merits,  and  of  the  u.se- 
lessuess  of  any  commeudation  on  our  part  of  a  book 
already  so  favorably  known  to  our  readers. — Boston 
Med.  and  Surg.  Journal,  Jan.  2.5,  1S66. 


Henry  C.  Lea's  Publications — {Medical  Jurisprudence,  &c.).      31 


T 


^AYLOR  [ALFRED  S.),  31. B., 

Lecturer  on  Med.  Juri-ip.  and  Chemisitry  in  Gny's  IJnspital. 

MEDICAL  JURISPRUDENCE.      Fifth  American,  from  the  seventh 

improved  and  enlarged  London  edition.  With  Notes  and  lieferences  to  American  Decisions, 
by  Edward  Hartshorne,  M.D.  In  one  large  octavo  volume  of  over  700  pages,  extra 
cloth.     $4  00. 

We  have  the  more  pleasure  in  expressing  our 
heariy  coincidence  with  the  general  verdjct  of  the 
two  profession.s.  medical  and  legal,  in  favor  of  this 
admii-able  treatise,  which,  like  the  one  just  men- 
tioufd,  although  printed  iuthe  manual  form,  is  really 
the  most  elaborate  work  on  the  subject  that  our  lite- 
rature possesses,  and  will  unquestionably  hold  its 
ground  as  the  standard  of  medical  jurisprudence  in 
this  country  so  long  as  it  shall  be  kept  by  its  author 
so  completely  up  to  the  mark  as  it  now  is. — Tlie Brit- 
ish and  Foreign  Medico- Ohirv.rgical  Review/:. 

Without  materially  increasing  the  bulk  of  this  most 
admirable  wurk,  we  have  a  new  edition  brought  close 
up  to  the  present  day,  with  old  errors  removed  and 
very  many  new  discoveries  added.  This  is  a  work 
well  worthy  the  high  position  of  its  author,  aud  a 
fair  representative  and  exponent  of  the  state  of  foren- 
sic medicine  in  this  country,  second  to  none,  we  ven- 
ture to  say,  in  the  woi'ld.  To  attain  this  every  chapter 
has  undergone  a  close  revision,  and  many  new  cases 
and  observations  have  been  added;  at  the  same  time 
no  extensive  changes  have  been  made  because  un- 
called for.  It  would  be  a  waste  of  time  to  attempt 
any  description  of  this  work,  which  must  have  found 
its  way  to  the  bookshelf  of  almost  every  practitioner 


Taylor's  Medical  Jurisprudence  has  been  the  text- 
book in  our  colleges  for  years,  and  the  present  edi- 
tion, with  the  valuable  additions  made  by  the  Ameri- 
can editor,  rendiu'  it  (he  most  standard  work  of  the 
day,  on  the  peculiar  province  of  medicine  on  whicli 
it  treats.  The  American  editor,  Ur.  Hartshorne,  has 
done  his  duty  to  the  text,  and,  upim  the  whole,  we 
cannot  but  consider  this  volume  the  best  and  richest 
treatise  on  medical  jurisprudence  in  our  language. — 
Brit.  Am.  Med.  Journal. 

The  presentation  to  the  profession  of  a  new  and  im- 
proved edition  of  this  well-known  and  de-ervedly 
popular  work  cannot  be  looked  upon  otherwise  than 
as  a  subject  of  congratulation.  The  book  has  many 
merits.  It  is  brief,  it  is  comprehensive;  it  treats  in  a 
clear  aud  satisfactory  manner  upon  a  large  number 
of  medico-legal  subjects,  the  most  interesting  and  im- 
portant that  can  he  presented  to  the  attention  of  the 
physician,  and  the  completeness  of  the  work  Is  en- 
hanced, especially  to  the  American  reader,  by  the 
appropriate  though  not  vei'y  copious  notes  and  re- 
ferences to  recent  American  cases,  by  Dr.  Hartshorne. 
— Chicago  Med.  Jour. 

We  need  hardly  say  that  this  work  is  quite  beyond 
the  pale  of  criticism,  and  that  all  we  have  to  do  is  to  |  in  the  kingdom  ;  those  who  have  it  not  should  pos- 
couLrratulate  the  profession  on  having  its  contents  sess  it  forthwith.  There  is  no  more  useful  work  of 
again  laid  before  them,  in  1861,  in  a  thoroughly  re-  !  reference  on  this  or  any  subject. — London  MedUxil 
vised  condition. — Briti-i-h  Med.  Journal.  \  Review. 


■DY  THE  SAME  AUTHOR.  

OX  POISONS,  IN  RELATION  TO  MEDICAL  JURISPRUDENCE 

AND  MEDICINE.     Second  American,  from  a  second  and  revised  London  edition.     In  one 
large  octavo  volume  of  766  pages,  extra  cloth.     $5  00. 


TYINSLOW  [FORBES],  M.D.,  D.  G.L.,  Sfc. 


ON  OBSCURE   DISEASES  OF  THE  BRAIN  AND    DISORDERS 

OF  THE  MIND;  their  incipient  Symptoms,  Pathology,  Diagnosis,  Treatment,  and  Pro- 
phylaxis. Second  American,  from  the  third  and  revised  English  edition.  In  one  handsome 
octavo  volume  of  nearly  600  page.?,  extra  cloth.     $4  25.      I^Jiist  Issued.) 

SUMMARY  OF  CONTENTS. 
Chapter  I.  Introduction — II.  Morbid  Phenomena  of  Intelligence — III.  Premonitory  Symp- 
toms of  Insanity — IV.  Confessions  of  Patients  after  Ptecovery — V.  State  of  the  Mind  during 
Piecovery — VI.  Anomalous  and  Masked  Affections  of  the  Mind — VII.  Stage  of  Consciousness — 
VIII.  Stage  of  Exaltfition — IX.  Stage  of  Mental  Depression — X.  Stage  of  Aberration — XI.  Im- 
pjairment  of  Mind — XII.  Morbid  Phenomena  of  Attention — XIII.  Morbid  Phenomena  of  Memory 
— XIV.  Acute  Disorders  of  Memory — XV.  Chronic  Affections  of  Memory — XVI.  Perversion  and 
Exaltation  of  Memory — XVII.  Psychology  and  Pathology  of  Memory — XVIII.  Morbid  Pheno- 
mena of  Motion — XIX.  Morbid  Phenomena  of  Speech — XX.  Morbid  Phenomena  of  Sensation — 
XXI.  Morbid  Phenomena  of  the  Special  Senses — XXII.  Morbid  Phenomena  of  Vision,  Hearing, 
Tiiste,  Touch,  and  Smell — XXIII.  Morbid  Phenomena  of  Sleep  and  Dreaming — XXIV.  Morbid 
Phenomena  of  Organic  and  Nutritive  Life — XXV.  General  Principles  of  Pathology,  Diagnosis, 
Treatment,  and  Prophylaxis. 


Of  the  merits  of  Dr.  Winslow's  treatise  the  profes- 
t-ioD  has  snflicicntly  judged.  Jt  has  taken  its  place  in 
the  front  rank  of  the  works  upon  the  special  depart- 
ment uf  practical  mfdicine  to  wliich  it  per  aius. — 
Ciw.innoli  Journal  (if  Medicine,  March,  1800. 

It  JH  an  interesting  volume  that  will  amply  repay 
for  a  careful  perusal  by  all  intelligent  rejfters  — 
Chicago  Med  E.ca'ininer,  Feb.  18G0. 

A  work  which,  like  the  present,  will  largely  aid 
the  practitioner  in  recognizing  and  arresting  tlie  first 
in:(idioiis  advances  of  cerebral  and  mental  disease,  is 
one  of  immense  practical  value,  aud  demands  earnest 
attention  aud  diligent  study  on  the  part  of  all  who 
have  embraced  the  medical  profession,  and  have 
tliereby  undertaken  responsibilities  in  which  the 
■wellare  and  happiness  of  individuals  and  families 
are  largely  involved.  We  shall  therefore  close  this 
brief  and  necessarily  very  imperfect  notice  of  Dr. 
Wiuslow's  great  and  classical  work  by  exprenBiug 


our  conviction  that  it  is  long  since  so  important  and 
beautifully  written  a  volume  has  issued  from  the 
British  medical  press.  The  details  of  the  maua,ge- 
raent  of  confirmed  cases  of  insanity  more  nearly  in- 
terest those  who  have  made  mental  diseases  their 
special  study;  but  Dr.  Winslow's  masterly  exposi- 
tion of  the  early  symptoms,  and  his  grapliic  descrip- 
tions of  the  insidions  advances  of  incipient  insanity, 
togeiher  with  his  judicious  observations  on  the  treat- 
ment of  disorders  of  the  mind,  should,  we  repeat,  be 
carefully  studied  by  all  who  have  undertaken  the 
respijusibiUties  of  medical  practice. — Dabtin  Medical 
Pre.iH. 

It  is  (he  most  interesting  as  well  as  valuable  book 
that  we  have  seen  for  a  long  time.  It  is  truly  fasci- 
nating— Am.  Jour.  Med.  Hcienaen. 

Dr.  Winslow's  work  will  undoubtedly  occupy  an 
unii<iie  position  in  the  medico-psycliol.pgjcal  litera- 
ture uf  liiift  country. — London  Med.  Jievcew. 


32 


Henky  C.  Lea's  Publications. 


INDEX    TO    CATALOGUE, 


Abel  and  Bloxam's  Handtiook  of  Chemistry 
Allen's  Dissector  and  Practical  Anatomist 
American  Journal  of  the  Medical  Sciences 
Anatomical  Atlas,  by  Sinilli  and  Horner 
Ashtou  on  tbe  Kectum  and  Anus  . 
Asbwell  on  Diseases  of  Females  . 
Blakiston  on  the  Chest    .... 
Brinton  on  the  Scomach 
Barclay's  Medical  Diagnosis  . 
Barlow's  Practice  of  Bledicine 
Bartlett  on  Fevers  of  the  United  States 
Barwell  on  the  Joints     .... 
Beale  on  the  Laws  of  Health 
Bennet  (Henry)  on  Diseases  of  the  Uterus 
Bennet's  Review  of  Uterine  Pathology 
Bowman's  (John  E.)  Practical  Chemistry 
Bowman's  (John  E.)  Medical  Cliemistry 
Brande  &  Taylor's  Chemistry 
Brodie's  Clinical  Lectures  un  Surgery  . 
Brown  on  the  Surgical  Diseases  of  Women 
Buckler  on  Bronchitis     .... 
Bucknill  aud  Tuke  on  Insanity 
Budd  on  Diseases  of  the  Liver 
Bumstead  on  Venereal    .... 
Carpenter's  Human  Physiology    . 
Carpenter's  Comparative  Physiology   . 
Carpenter  on  the  Microscope 
Ciirpenter  on  the  Use  and  Abuse  of  Alcohol 
Carson's  Synopsis  of  Materia  Medica    . 
Christison  aud  Griffith's  Dispensatory 
Churchill's  System  of  Midwifery  . 
Churchill  on  Diseases  of  Females 
Churchill  on  Diseases  of  Children 
Churchill  on  Puerperal  Fever 

Clymer  on  Fevers 

Colombat  de  I'lsere  on  Females,  by  Meigs 
Condie  on  Diseases  of  Children 
Cooper's  (B.  B.)  Lectures  on  Surgery    . 
Cooper  (Sir  A.  P.)  on  the  Testis,  &c.      . 
Curling  on  Diseases  of  the  Te>tis  . 
Cyclop"edia  of  Practical  Medicine  . 
Daltou's  Human  Physiology  . 
De  Jongh  on  Cod-Liver  Oil 
Dewees's  System  of  Midwifery 
Dewees  on  Diseases  of  Females 
Dewees  on  Diseases  of  Children    . 
Dickson's  Practice  of  Medicine 
Druitt's  Modern  Surgery 
DungUsou's  Medical  Dictionary    . 
Dunglison's  Human  Physiology     . 
Dunglison  on  New  Remedies 
Dunglison's  Therapeutics  and  Materia  Med 
Ellis's  Medical  Formulary,  by  Thomas 
Erich.sen's  System  of  Surgery 
Fergussou's  Operative  Surgery 
Flint  on  Respiratorj'  Organs  . 

Flint  on  the  Heart 

Flint's  Practice  of  Medicine   . 
Fownes's  Elementary  Chemistry  . 
Frick  on  Renal  Affections 
Gardner's  Medical  Chemistry 

Gibson's  Surgery 

Gluge's  Pathological  Histology,  by  Leidy 
Graham's  Elements  of  Chemistry  . 
Gray's  Anatomy      ..... 
Griffith's  (R.  S.)  Universal  Formulary  . 
Griffith's  (J.  W.)  Manual  on  the  Blood,  &c. 
Gross  on  Urinary  Organs 
Gross  on  Foreign  Bodies  in  Air-Passages 
Gross's  Principles  and  Practice  of  Surgery 
Gross's  Pathological  Anatomy 
Habershon  on  Alimentary  Canal   . 
Hamilton  on  Dislocations  and  Fractures 
Harrison  on  the  Kevvoii.s  System  . 
Hoblyn's  Medical  Dictionary 

Hodge  on  Women 

Hodge's  Obstetrics 

Holland's  Medical  Notes  and  Reflections 
Horner's  Anatomy  and  Histology 
Hughes  on  Auscultation  and  Percussion 
Hiliier'a  Handbook  of  Skin  Diseases    . 


PAGE 

12  I 

l\ 
7 


Jones's  (T.  W.)  Ophthalmic  Medicine  and  Surg, 
Jones  and  Sieveking's  Pathological  Anatomy 
Jones  (C.  Haudlield;  on  JN'ervous  Disorders 
Kirkes'  Physiology  .... 

Knapp's  Chemical  Technology 
Lalleiaand  and  Wilson  on  Spermatorrhosa 
La  Roche  on  Yellow  Fever     .         . 
La  Roche  on  Pneumonia,  &o. 
Laurence  and  Moon's  Ophthalmic  Surgerj^ 
Laycock  on  Medical  Observation  . 
Lenmaun's  Physiological  Chemistry,  2  vols, 
Lehmann's  Chemical  Physiology  . 
Ludlow's  Manual  of  Examinations 

Lyons  on  Fever 

jilaclise's  Sui'gical  Anatomy  . 

iMalgaigne's  Operative  Surgery,  by  Brittan 

Marwick's  Examination  of  Urine  . 

Mayne's  Dispensatory  and  Formulary 

Mackenzie  on  Diseases  of  the  Eye 

Medical  News  and  Library     . 

Meigs's  Obsretrics,  the  Science  and  the  Art 

Meigs's  Letters  on  Diseases  of  Women 

Meigs  on  Puerperal  Fever 

Miller's  System  of  Obstetrics 

iMiller's  Practice  of  Surgery  . 

Miller's  Principles  of  Surgery 

Montgomery  on  Pregnancy     . 

JMorland  on  Urinary  Oi-gans   . 

Morland  on  Urremia         .... 

Neill  and  Smith's  Compendium  of  Med.  Science 

Neligan's  Atlas  of  Diseases  of  the  Skin 

Neligan  on  Diseases  of  the  Skin ,   . 

Prize  Essays  ou  Consumption 

Parrish's  Practical  Pharmacy 

Peaslee's  Human  Histology    . 

Pirrie's  System  of  Surgery 

Pereira's  Mat.  Medica  and  Therapeutics,  abrid 

Qualn  and  Sharpey's  Anatomy,  by  Leidy 

Roberts  on  Urinary  Diseases  . 

Ramsbotham  on  Parturition  . 

Reese  on  Blood  and  Urine 

Ricord's  Letters  on  Syphilis,  by  Lattimore 

Rigby  on  Female  Diseases 

Rigby's  Midwifery 

Rokitanaky's  Pathological  Anatomy     . 

Royle's  Materia  Medica  and  Therapeutics 

Sargent's  Jlioor  Surgery 

Sharpey  aud  Quain's  Anatomy,  by  Leidy 

Simon's  General  Pathology     ... 

Simpson  on  Females        .... 

Skey's  Operative  Surgery 

Slade  on  Diphtheria        .... 

Smith  (H.  H.)  and  Horner's  Anatomical  Atl 

Smith  (Tyler)  ou  Parturition 

Smith  (Edward)  on  Consumption  . 

Solly  on  Anatomy  and  Diseases  of  the  Brai 

StiU6's  Therapeutics        .... 

Salter  on  Asthma 

Tanner's  Manual  of  Clinical  Medicine  . 
Taylor's  Medical  Jurisprudence    . 

Taylor  on  Poisons 

Todd  and  Bowman's  Physiological  Anatomy 
Todd  on  Acute  Diseases  .        .        .        . 
Toynbee  on  the  Ear         .... 
Walshe  on  the  Lungs      .... 
Walshe  on  the  Heart       .... 
Watson's  Practice  of  Physic  . 
West  on  Diseases  of  Females 
West  on  Diseases  of  Children 
West  on  Ulceration  of  Os  Uteri 
What  to  Observe  in  Medical  Cases 
Williams's  Principles  of  Aledicine 
Wilson'S|  Human  Anatomy     . 
Wilson's  Dissector  ..... 
Wilson  ou  Diseases  of  the  Skin 
Wilson's  Plates  on  Diseases  of  the  Skin 
VVilsou's  Handbook  of  Cutaneous  Medicine 
Wilson  on  Healthy  Slvin 
Wilson  on  Spermatorrhoja 
Winslow  ou  Brain  and  Mind 


ADE 

30 
1.3 
20 


COLUMBIA  UNIVERSITY 

This  book  is  due  on  the  date  indicated  below,  or  at  the 
expiration  of  a  definite  period  after  the  date  of  borrowing, 
as  provided  by  the  rules  of  the  Library  or  l)y  special  ar- 
rangement with  the  Librarian  in  charge. 


DATE  BORROWED 

DATE  DUE 

DATE  BORROWED 

DATE  DUE 

C28(636)M50 

D17 
1864 


ysiology 


i 


\ 


